PPP Notes - Site Lighting

SITE ELECTRICAL UTILITIES

 (These notes are compiled from AGS)

SITE LIGHTING

 

• Creating good design for site lighting is not just about picking the latest technology or the best fixture.  It is about using lighting to convey the overall story of a project. 
• The story may be one of safety in a casino parking lot or it may be one of excitement in an outdoor mall where visitors can gather with their families for an evening to have dinner and see a movie.
• Site lighting design requirements vary from project to project, and so need to be defined with the individual project team prior to preparing a design.
• Site lighting requirements typically include lighting pedestrian pathways, landscaping, landscape features, water features, and architectural features such as statuary and adjacent public roadways, parking areas, and nearby facades.
• Site lighting design, at its core, is about lighting the environment in a manner that responds to the desired function of the guests within the space.
• There may be multiple functions such as wayfinding, creating gathering spaces, interacting with the organic and built environments, and meeting security requirements, which all must be taken into account.
• The overall design intent of the space must allow for these functions to coexist seamlessly, or the guest experience will be negative.
• As a part of the design preparation, designers will want to familiarize themselves with the landscape design and current foliage specifications on the project.
• Lighting fixtures can be used to highlight trees, accent shrubbery, and be mounted in trees to light the path below.
• It is important to know which trees are deciduous and which trees retain their canopies when making these determinations.
• It is also highly recommended that lighting designers work closely with the landscape architect to understand which trees will allow the attachment of lighting hardware and mounting straps.
• Once the site lighting tasks and requirements have been determined, the designer can begin selecting fixtures, determining lamp types, and preparing the layout.

 

SITE LIGHTING REGULATIONS AND CODES

 

• Other factors to consider when designing site lighting are local and national energy codes, any locality-specific dark-sky ordinances, and the current lighting levels in the surrounding and adjacent areas.
• The International Dark-Sky Association (IDA) is a nonprofit group whose mission is “to preserve and protect the nighttime environment and our heritage of dark skies through quality outdoor lighting.”
• This association (www.darksky.org) has been an active voice in the creation of many of the local dark-sky ordinances.
• Several calculation programs are available to help verify the illuminance levels are being met in the site lighting design. 
• AGI32 (www.agi32.com) is commonly used for site lighting studies as is LumenMicro by Lighting Technologies (www.lighting-technologies.com).
• The most difficult part of creating a good lighting design is to meet all of the functional and code requirements of a site while mixing in the desired aesthetics of the project.
• Providing the right nighttime identity for a site is key to making any project a success.

 

SITE LIGHTING DOCUMENTATION

 

• Required documentation for the lighting design submittal will vary from project to project, but the basic elements will remain the same.
• A minimum of suggested documentation would include:
• A layout depicting the design intent
• Fixture cut sheets and specifications showing fixtures desired on the project.
• Mounting details showing any special integration requirements.

 

AREA LIGHTING

 

• Path lighting fixtures generally include pole/post lighting, bollards, and step lights.
• Pole lighting can be decorative to match the architecture, make a statement, or be purely functional.
• Pole, post, and bollard heights and spacing are determined by calculating the desired and/or required illuminance values, along with creating a layout that meets the aesthetic qualities as determined by the project design team.
• As a general rule, the minimum mounting height should be no less than one-half the maximum project distance from a single fixture head.
• When using poles, posts or bollards, designers should be prepared to coordinate anchor bolt details and the need for any additional foundations required to meet local wind-loading requirements.
• Project engineers should be consulted, as well as the fixture manufacturer, to confirm the product can meet the wind-loading requirements.
• Mounting details should be customized for any site-specific requirements, and the specified manufacturer should be treated as a valuable resource for the information needed to complete this effort.
• It is also highly recommended that the Illuminating Engineering Society of North America (IESNA) by a key resource for all projects located within North America. 
• The IESNA has compiled a series of recommended lighting requirements and illuminance values for many of the tasks involved in creating the site lighting.
• There is a variety of lighting illuminance levels, depending on the adjacent architecture.
• For example, a bank parking lot may require higher levels of illuminance, due to security issues, than those of a library parking lot on the same street.
• The KIM theory of relativity says, “Poles belong in parking lots.  And, once you leave the parking lot, the outdoor lighting should become less and less conspicuous until it becomes an integral part of the architecture.”
• In addition, the luminaire style and geometry should remain consistent.  
• SITE/ROADWAY ZONE LIGHTING: Parking lots and roadways require luminaires on 20’-40’ poles to efficiently light these large areas.  Therefore, this lighting becomes dominant, and sets the design and style for all other lighting as you progress towards the building.
• PEDESTRIAN ZONE LIGHTING: As you leave the parking lot and transition to pedestrian areas, poles should decrease in height, to 10’-16’.  In addition, luminaires should decrease in scale, and can have more decorative features to be appreciated at the pedestrian level.
• LANDSCAPE/PATH ZONE LIGHTING: Near the building, luminaires should begin to disappear, blending into the landscape and hardscape elements.
• BUILDING/PERIMETER LIGHTING: No pole-mounted luminaires should ever be used near the building, as they will dominate the architecture.  The only exception would be the use of decorative luminaires to delineate entrances to the structure.  Building mounted, architecturally compatible fixtures should be almost invisible.

PPP Notes - Runoff Control

RUNOFF CONTROL SYSTEMS

 (These notes are compiled from AGS)

NATURAL WETLAND SYSTEMS

 

• Wetlands naturally detain and filter water.
• Scattered throughout the United States, from tropical areas to tundra, they form in depressions in the landscape where the water table is near or at the surface of the soil.
• They may be as small as a tabletop or span tens of thousands of acres.
• There is no single, correct, ecologically sound definition for wetlands, primarily because of their diversity. 
• These systems are an important part of the ecosystem because they produce food and timber, purify drinking water, absorb and store floodwater, suppress storm surges, and help maintain biodiversity.
• Water is supplied to a wetland either by surface sources (i.e., streams or rivers) or by groundwater.
• The sensitivity of wetlands determines appropriate buffer distances between them and developed areas.
• Buffers, which may range from 30 to 300 ft. or more, should respond to the effect runoff may have on the wetland ecosystem.  (Consult a wetlands scientist to formulate buffer distances).
• In general, four wetland sensitivity issues should be taken into account:
• HYDROLOGY: The wetland’s source of water could be altered by development.
• VEGETATION: The plant species in a wetland have different levels of hardiness.
• ECOLOGICAL STATE: More pristine systems are more sensitive to development and runoff pollution.
• ANIMAL SPECIES: Nesting birds, for example, need greater buffer distances than wintering waterfowl.

 

ON-SITE RUNOFF CONTROL MEASURES

 

• Architects can use several on-site measures to control runoff in development projects.
• One of the most commonly used measures is a simple open storage area for runoff.
• The configuration of such open systems varies, depending on the desired level of pollutant treatment.
• Typically called storage ponds, retention basins, or (when made to resemble a natural environment) a constructed stormwater wetland, open systems generally operate more thoroughly with increased retention time.
• Simple storage ponds are typically dry between storms after runoff has evaporated or infiltrated the groundwater.
• Dry ponds sometimes include a wet lower area for additional runoff retention.
• Wet ponds are permanently wet, allowing pollutants to settle to the bottom. 
• Wet ponds that extend runoff retention time with control devices can remove a very high percentage of particulate pollutants.
• Constructed stormwater wetlands (engineered, shallow marshlike areas) retain runoff for long periods), allowing pollutants to settle out of the water column and providing biological, chemical, and physical processes for breaking down pollutants.
• Wetland vegetation slows the velocity of stormwater, reducing erosion and allowing pollutants to settle.
• Many organic and inorganic compounds are removed from wetlands by the chemical processes of absorption, precipitation, and volatilization.
• Constructed stormwater wetlands can also filter excess nutrients such as nitrogen and phosphorous contained in runoff from gardens and septic tanks.
• To correctly size a wetland used for stormwater runoff control, consider the total volume and velocity of water entering and leaving the system.
• Potential advantages of using constructed stormwater wetlands are that they have relatively low capital and operating costs, off consistent compliance with permit requirements, and greatly reduce operational and maintenance costs.

 

STORMWATER WETLANDS

 

• Stormwater wetlands can be defined as constructed systems explicitly designed to mitigate the effects of stormwater quality and quantity on urban development.
• They temporarily store stormwater runoff in shallow pools that create growing conditions suitable for emergent and riparian wetland plants.
• In combination, the runoff storage, complex microtopography, and emergent plants in the constructed wetland form an ideal matrix for the removal of urban pollutants.
• Unlike natural wetlands, which often express the underlying groundwater level, stormwater wetlands are dominated by surface runoff.
• Storm water wetlands can best be described as semitidal, in that they have a hydroperiod characterized by a cyclic pattern of inundation and subsequent drawdown, occurring 12 to 30 times a year, depending on rainfall and the imperviousness of the contributing watershed.
• Storm water wetlands usually fall into one of four basic designs:
• SHALLOW MARSH SYSTEM: The large surface area of a shallow marsh design demands a reliable groundwater supply or base flow to maintain sufficient water elevation to support emergent wetland plants.  Shallow marsh systems take up a lot of space, requiring a sizeable contributing watershed (often more than 25 acres) to support a shallow permanent pool.
• POND/WETLAND SYSTEM:  A pond/wetland design utilizes two separate cells for stormwater treatment., a wet pond and a shallow marsh.  The multiple functions of the latter are to trap sediments, reduce incoming runoff velocity, and remove pollutants.  Pond/wetland systems consume less space than shallow marsh systems because the bulk of the treatment is provided by a deep pool rather than a shallow marsh.
• EXTENDED DETENTION WETLAND: In extended detention wetlands, extra runoff storage is created by temporarily detaining runoff above the shallow marsh.  This extended detention feature enables the wetland to occupy less space, as temporary vertical storage partially substitutes for shallow marsh storage.  A growing zone is created along the gentle side slopes of extended detention wetlands, from the normal pool level to the maximum extended detention water surface.
• POCKET WETLANDS: Pocket wetlands are adapted to serve small sites (from 1 to 10 acres).  Because the drainage area is small, pocket wetlands usually do not have a reliable base flow, creating a widely fluctuating water level.  In most cases, water levels in the wetland are supported by excavating down to the water table.  In drier area, a pocket wetland is supported only by storm water runoff, and during extended periods of dry weather it will have no shallow pool at all (only saturated soils).  Due to their small size and fluctuating water levels, pocket wetlands often have low plant diversity and poor wildlife habitat value.
• The selection of a particular wetland design usually depends on three factors:
• AVAILABLE SPACE
• CONTRIBUTING WATERSHED AREA
• DESIRED ENVIRONMENTAL FUNCTION
• However, storm water wetlands are not typically located within delineated natural wetland areas, which provide critical habitat and ecosystem services, and are protected under local, state, and federal statutes.
• It’s also important to point out that storm water wetlands should not be confused with constructed wetlands, which are used to mitigate the permitted loss of natural wetlands under wetland protection regulations.
• The primary goal of wetland mitigation is to replicate the species diversity and ecological function of the lost natural wetland, whereas the more limited goal of storm water wetlands is to maximize pollutant removal and create generic wetland habitat.
• Storm water wetlands are also distinguished from natural wetlands that receive storm water runoff as a consequence of upstream development.
• Although not intended for stormwater treatment, wetlands influenced by stormwater are common in urban settings. 
• Storm water runoff that becomes a major component of the water balance of a natural wetland can severely alter the functional and structural qualities of the wetland. 
• The end result is a storm water-influenced natural wetland that is more characteristic of a storm water wetland than a natural one.

 

SHALLOW MARSH SYSTEM

 

• Most of the shallow marsh system is 0 to 18 inches deep, a depth that creates favorable conditions for the growth of emergent wetland plants. 
• A deeper forebay is located at the major inlet, and a deep micropool is situated near the outlet.

 

POND/WETLAND SYSTEM

 

• The pond/wetland system consists of a deep pond that leads to a shallow wetland. 
• The pond removes pollutants and reduces the space required for the system.

 

EXTENDED DETENTION WETLAND

 

• The water level in an extended detention wetland can increase by as much as 3 ft. after a storm, returning to normal levels within 24 hours.
• As much as half the total treatment volume can be provided as extended detention storage, which helps protect downstream channels from erosion and reduces the space needed for the wetland.

 

PPP Notes - Civil and Mechanical Utilities

SITE CIVIL/MECHANICAL UTILITIES

 (These notes are compiled from AGS)

SUBSURFACE DRAINAGE SYSTEMS

 

• Subsurface drainage systems are very different engineering designs from surface drainage systems. 
• Surface drainage systems intercept and collect stormwater runoff and convey it away from building and site with the use of large inlets and storm drains.
• Subsurface drainage systems typically are smaller in size and capacity and designed to intercept the slower underground flows of a natural groundwater table, underground stream, or infiltration of soils from surface sources. 
• Surface and subsurface systems typically require discharge either through a pumping station or by gravity drainage to an adequate outfall.

 

STORM DRAINAGE UTILITIES

 

• Storm drainage utilities are designed to collect and dispose of rainfall runoff to prevent the flow of water from damaging building structures (through foundation leakage), site structures, and the surface grade (through erosion).
• The two basic types of surface drainage are the open system and the closed system.
• The OPEN SYSTEM, which utilizes a ditch/swale and culvert, is used in less densely populated, more open areas where the flow of water above grade can be accommodated fairly easily.
• The CLOSED SYSTEM, which utilizes pipes, an inlet/catch basin, and manholes, is used in more urban, populated areas, where land must be used efficiently and water brought below the surface quickly to avoid interference with human activity.
• The two systems are commonly combined where terrain, human density and land uses dictate.
• A pervious or porous paving is often used for parking and other hard site surfaces.
• This drainage system allows water to percolate through the paved surface into the soil; similar to the way the land would naturally absorb water.

 

DESIGN CONSIDERATIONS FOR SURFACE DRAINAGE SYSTEMS

 

• When designing surface drainage systems, follow these guidelines:
• Lay out all slopes, grates, swales, and other drainage features according to the ADA, without restricting accessible routes for persons with disabilities.  Refer to applicable codes, standards, and regulations for accessibility requirements.
• Lay out grades so runoff can safely flow away from buildings.  If drains become blocked, do not allow backed-up water to accumulate around the foundation. 
• Keep in mind that an open system, or one in which water is kept on top of the surface as long as possible, is generally more economical than a closed system.
• Keep in mind that an open system, or one in which water is kept on top of the surface as long as possible, is generally more economical than a closed system.
• Consider the effect of ice forming on the surface when determining slopes for vehicles and pedestrians.
• Consult local codes on such criteria as intensity and duration of rainstorms and allowable runoff for the locality.
• Note that formulas given in this discussion are meant for approximation only.  Consult a qualified engineer or landscape architect to design a site-specific system.

 

POROUS PAVING SYSTEMS

 

• Porous paving materials, methods for sizing channels, and design considerations for porous paving systems are all vital for quality landscape design.

 

POROUS PAVING MATERIALS

 

• The two principal types of porous paving are monolithic surfacing material and unit pavers.
• MONOLITHIC POROUS PAVING is stone aggregate bound with asphalt or Portland cement.  The aggregate must be sorted to exclude the “fines” or sand-sized particles that normally fill the voids between larger pieces.  Without the fines, water is able to run through the paving material.  Generally, porous asphalt and concrete are both strong enough for parking and roadway surfaces and pedestrian uses.
• PRECAST CONCRETE UNIT PAVERS, with shapes that allow water to flow through them, can also give surface stability for parking or driveways.  Paver types are available for exposed placement, or for burial just below the surface.  In the latter case, the soil-pea gravel or vegetation in the pavers is exposed and can help percolate precipitation into the ground.
• To reduce runoff and increase water absorption, porous paving must be underlaid with a bed of unbound aggregate. 
• The unbound aggregate acts as a structural support and forms a reservoir to hold precipitation until it can percolate into the soil. 
• Use of porous paving may permit use of a significantly smaller and simpler storm drainage system.

 

METHOD FOR SIZING CHANNELS

 

• Channels and pipes for handling water runoff may be sized by determining the flow of water (Q) with the formula Q = Va. 
• “V” is the velocity of the runoff water in ft./sec. as determined by the Manning formula, and “a” is the cross-sectional area of water given in square feet. 
• For a given “Q,” adjust the channel or pipe shape, size, and/or slope to obtain the desired velocity (one that will not erode earth, grass ditches, or other features).
• The Manning formula is V = (1.486/n) x (r x 0.67) x (S x 0.5), in which:
• n = values relating to surface characteristics of channels
• r = hydraulic radius
• S = slope drop in ft./length
• Use the formula for calculating runoff (Q = C x I x A) to determine the flow required for a site; compare it to the capacity of a channel sized according to the Manning formula to determine whether the channel design is satisfactory.
• Q = ratio of runoff in cubic feet per second
• C = ratio of runoff to rainfall
• I = rainfall intensity in inches per hour
• A = area of the watershed in acres

 

DESIGN CONSIDERATIONS FOR POROUS PAVING SYSTEMS

 

• Design considerations for working with porous paving systems include the following:
• Soils around porous paving installations must have a minimum percolation rate of about ½ in / hr., and should not be more than about 30% clay.  On sites where the slope is greater than 3%, terracing the paved areas allows the bottom of each reservoir to remain level.
• Proper specification and supervision are important in the installation of porous paving materials.  Soil under the reservoir must not be unduly compacted during construction.
• Porous concrete can withstand heavier loads than porous asphalt.  Because it does not soften in hot weather and may be more susceptible to freeze/thaw damage, it is better suited to warmer climates.  Additives may be introduced to improve cold climate performance.
• Porous asphalt has good freeze/thaw resistance, but is best suited for areas in which traffic is limited, such as employee parking.
• While clogging of monolithic porous paving is generally not a problem, recommended maintenance may include use of a hydrovac once or twice a year, as well as the prompt removal of leaves and windblown sand.
• The reservoir below porous paving has no fixed depth but is designed according to the slope of the site, the soil percolation rate, and the size of the design storm.  Consult a civil engineer or landscape architect.

 

PPP Notes - Trees and Plants

PLANTING OF TREEES AND SHRUBS

 (These notes are compiled from AGS)

TREES PLANTS AND GROUND COVERS

 

• The physical environment of the site, the design needs of the project, and the design character of the trees are all factors that must be considered in selecting trees and preparing a landscape plan for a building.
• Soil conditions (acidity, porosity) at the site, the amount and intensity of sunlight and precipitation, and the seasonal temperature range in the area create the physical environment in which trees must be able to survive.
• In addition, it is essential to consider how the location and topography of the site will direct the wind, resulting in cold winds and cooling breezes that can affect the health of trees.
• Trees can be used to address the design needs of a project by directing pedestrian or vehicle movement, framing vistas, screening objectionable views, and defining and shaping exterior space.
• Trees can also be used to modify the microclimate of a site and to help conserve building energy use from heating, cooling, and lighting systems.
• The design character of the trees themselves plays a part in which species are best suited for a particular application.
• The shape of a tree can be columnar, conical, spherical, or spreading, and the resulting height and mass will change over time as the tree matures.
• Some trees grow quickly, and others more slowly, and their color and texture varies from coarse to medium to fine, affecting their character.
• The appearance of deciduous trees changes with the seasons, while the effect of an evergreen remains relatively constant.

 

PHYSICAL CHARACTERISTICS

 

• CROWN: The head of foliage of a tree
• LEAVES: The foliage unit of a tree that function primarily in food manufacturing by photosynthesis.
• ROOTS: Anchors a tree and helps hold against soil erosion.
• ROOT HAIRS: Absorb minerals from the soil moisture and send them as nutrient salts in the sapwood to the leaves.
• HEARTWOOD: Nonliving central part of a tree, gives strength and stability.
• ANNUAL RINGS: Reveal the age of a tree by showing yearly growth.
• OUTER BARK: Aged inner bark that protects tree from desiccation and injury.
• INNER BARK (PHLOEM): Carries food from leaves to branches, trunk, and roots.
• CAMBIUM: Layer between xylem and phloem where cell-adding growth occurs, new sapwood to inside and new inner bark outside.
• SAPWOOD (XYLEM): Carries nutrients and water to leaves from roots.

 

GLARE PROTECTION

 

• Trees protect viewer from glare of surfaces such as water, paving and glass.
• The vertical angle of the sun changes seasonally; therefore, the area of a building subject to the glare of reflected sunlight varies.
• Plants of various heights can screen sun (and artificial light) glare from adjacent surfaces.

 

AIR INFILTRATION

 

• Large masses of plants physically and chemically filter and deodorize the air, reducing air pollution.
• Particulate matter trapped on the leaves washes to the ground during rainfall.
• Gaseous pollutants are assimilated by the leaves.
• Fragrant plants can mechanically mask fumes and odors.  Also, these pollutants are chemically metabolized in the photosynthesis process.

 

WIND PROTECTION

 

• Shelterbelt (providing trees) wind protection reduces evaporation at ground level, increases relative humidity, lowers the temperature in summer and reduces heat loss in winter, and reduces blowing dust and drifting snow.
• The amount of protection afforded is directly related to the height and density of the shelterbelt.

 

SHADE PROVISION

 

• In summer, trees obstruct or filter the strong radiation from the sun, cooling and protecting the area beneath them.
• In winter, evergreen trees still have this effect, whereas deciduous trees, having lost their leaves, do not.

 

SOUND ATTENUATION

 

• A combination of deciduous and evergreen trees and shrubs reduces sound more effectively than deciduous plants alone.
• Planting trees and shrubs on earth mounds increases the attenuating effects of a buffer belt.

 

RUNOFF REDUCTION

 

• Leaves and branches are coated with thin films of water, holding it from running off.
• Branch structure channels water to dry area under the tree to be absorbed.
• Roots absorb water runoff from branches.
• Mature trees absorb or delay runoff from stormwater, and general design considerations are the topics addressed in this section.

 

PLANTING DETAILS

 

• Planting details for trees and shrubs, tips on soil improvement and general design considerations are topics to be addressed by all design professionals.

 

TREE PLANTING DETAILS

 

• These three guidelines will aid in the successful planting of trees:
• For container-grown trees, use fingers or small hand tools to pull the roots out of the outer layer of potting soil; then cut or pull apart any roots circling the perimeter of the container.  Incorporate commercially prepared mycorrhiza spores in the soil immediately around the root ball at rates specified by the manufacturer.
• During the design phase, confirm that water drains out of the soil; design alternative drainage systems as required.
• Thoroughly soak the tree root ball and adjacent prepared soil several times during the first month after planting, and regularly throughout the following two summers.
• Note that the planting process is similar for deciduous and evergreen trees.

 

SHRUB PLANTING DETAILS

 

• For successful shrub planting, follow these guidelines:
• For container-grown shrubs, use fingers or small hand tools to pull the roots out of the outer layer of potting soil; then cut or pull apart any roots that circle the perimeter of the container.  Incorporate commercially prepared mycorrhiza spores in the soil immediately around the root ball at rates specified by the manufacturer.
• Confirm that water drains out of the soil during the design phase; design alternative drainage systems as required.

 

SOIL IMPROVEMENT

 

• The quality of soil available for planting varies widely from site to site, especially after construction activity has occurred. 
• The nature of construction results in compaction, filling, contamination, and grading of the original soil on a site, rapidly making it useless for planting.
• Previous human activity at a site can also affect the ability of the soil to support plants.
• During the design phase, assumptions must be made regarding the probably condition of the soil after construction is complete.
• The health of existing or remaining soil determines what types of soil preparation will be required and the volume of soil to be prepared.
• Conditions will vary from location to location within a project, and details must be condition-specific.
• For large projects or extreme conditions, it is useful to consult an expert experienced in modifying planting soils at urban sites.
• To ensure good soil health at a project site, follow these guidelines:
• Whenever possible, connect the soil improvement area from tree to tree.
• Always test soil for pH and nutrient levels, and adjust these as required.
• Loosen soil with a backhoe or other large coarse-tilling equipment, when possible.  Tilling that produces large, coarse chunks of soil is preferable to tilling that results in fine grains uniform in texture.
• Make sure that the bottom of planting soil excavations is rough; to avoid matting of soil layers as new soil is added.  It is preferable to till the first lift (2 to 3 in.) of planting soil into the subsoil.

 

CONSTRUCTION AROUND EXISTING TREES

 

• Great care should be taken not to compact, cut, or fill the earth within the crown area of existing trees.
• Most tree roots are located in the top 6 to 18 in. of the soil, and often spread considerably farther than the drip line of the tree.
• Compaction can cause severe root damage and reduce the movement of water and air through the soil.
• To avoid compacting the earth, do not operate equipment or store materials within the crown spread.
• Before construction begins, inject the soil within the crown area of nearby mature trees with commercially prepared kelp-based fertilizer and mycorrhiza fungus developed to invigorate tree roots.
• Prune tree roots at the edge of the root save area, as roots pulled during grading can snap or split well into the root save area.
• Rot and disease that enters dying roots in compacted or filled areas can move into the tree if root pruning has not been carried out.
• Install tree protection fencing and silt protection at the limits of construction activity near trees.
• During construction, apply additional water in the canopy area to compensate for any root loss beyond the crown spread.
• Have all mature trees inspected by a certified arborist before construction begins, to identify any special problems.
• Remove all deadwood, and treat all trees for existing insect and disease problems.
• When possible, begin fertilization and problem treatments at least one full growing season before construction.
• Removal of significant portions of the crown will affect the health of a tree by reducing its ability to photosynthesize in proportion to the mass of its trunk. 
• Younger, healthier trees withstand construction impacts better than older trees.

 

GENERAL RANGE OF SOIL MODIFICATIONS AND VOLUMES

 

• GOOD SOIL (NOT PREVIOUSLY GRADED/COMPACTED)
• Min. Width – 6’ or twice the width of the root ball, whichever is greater.
• COMPACTED SOIL (NOT PREVIOUSLY GRADED)
• 15’
• GRADED SUBSOILS AND CLEAN FILLS WITH 5-35% CLAY
• 20’
• POOR-QUALITY FILLS, HEAVY CLAY SOILS, SOILS CONTAMINATED
• 20’

 

ROOT PRUNE TRENCH

 

• A root prune trench severs roots with a clean cut, protecting remaining roots from cracking, rot, and disease.
• Typically 3” or more in width and 18-24” in depth.
• Root prune trenches are typically cut with rock saws or trenchers, and filled after with soil.

 

UNDERGROUND UTILITY LINES NEAR EXISTING TREES

 

• Fewer roots are severed by tunneling under a tree than by digging a trench beside it.

 

TREE AND ROOT PROTECTION

 

• If construction operations must take place within the crown spread area, install 6 in. of wood chips on top of the soil to protect it.
• Use plywood matting over mulch in areas where equipment must operate. 
• Protect the trunk of the tree with planking loosely cabled around the tree to reduce scarring by equipment.
• Remove planking, matting, and mulch as soon as operations are finished. 
• A barrier such as that illustrated can keep construction equipment and personnel from compacting the soil around tree roots.

 

TREE PLANTING IN URBAN AREAS

 

• Traditional urban designs in which trees are regularly spaced in small opening within paved areas generally result in poor tree performance because such designs generally do not provide adequate soil for root growth, and ignore the fact that trees must significantly increase trunk size every year.
• Moreover, competition for space, both at ground level and below, is intense in urban areas.
• Although it is possible to design uncompacted soil volumes for trees under pavement, this is very expensive and the soil is never as efficient as that in open planting beds.
• Increasing trunk size can only be accommodated by using flexible materials that can change configuration over time.
• Urban designs that have flexible relationships between trees, paving, and planting beds and large areas of open planting soil offer the best opportunity for long-term tree health and lower maintenance costs.
• Areas of dense urban development leave little room for tree roots to develop.
• Large areas of pavement, competition with foundations and utilities for space belowground, and extensive soil compaction and disruption limit the amount of soil available for trees.
• When the area of ground around the tree is open to the rain and sun is less than 400 to 500 sq. ft. per tree, the following design guidelines should be followed to encourage the growth of large healthy trees.
• Five major parts of the tree structure must be accommodated in the design process:
• CROWN GROWTH: The tree crown expands every growing season at a rate of 6 to 18 in. per year.  Once the crown reaches a competing object such as a building or another tree canopy, the canopy growth in that area slows and then stops.  Eventually the branches on that side of the tree die.  As the canopy expansion potential is reduced, the overall growth rate and tree health are also reduced.
• TRUNK GROWTH: The tree trunk expands about ½ to 1 in. per year.  As the tree increases in size, the lower branches die and the trunk lengthens.  Tree trunks move considerably in the wind, especially during the early years of development, and are damaged by close objects.
• TRUNK FLARE: At the point at which the trunk leaves the ground, most tree species develop a pronounced swelling or flare as the tree matures.  This flare grows at more than twice the rate of the main trunk diameter and helps the tree remain structurally stable.  Any hard object placed in this area, such as a tree grate or confining pavement, will either damage the tree or be moved by the tremendous force of this growth.
• ZONE OF RAPID ROOT TAPER: Tree roots begin to form in the trunk flare and divide several times in the immediate area around the trunk.  In this area, about 5 to 6 ft. away from the trunk, the roots rapidly taper from about 6 in. in diameter to about 2 in.  Most damage to adjacent paving occurs in this area immediately around the tree.  Keeping the zone of rapid taper free of obstructions is important to long-term tree health.  Once a tree is established, the zone of rapid taper is generally less susceptible to compaction damage than the rest of the root zone.
• ROOT ZONE: Tree roots grow radially and horizontally from the trunk and occupy only the upper layers (12 to 24 inches) of the soil.  Trees in all but the most well-drained soils do not have taproots.  A relationship exists between the amount of tree canopy and the volume of root-supporting soil required.  This relationship is the most critical factor in determining long-term tree health.  Root-supporting soil is generally defined as soil with adequate drainage, low compaction, and sufficient organic and nutrient components to support the tree.  The root zone must be protected from compaction both during and after construction.  Root zones that are connected from tree to tree generally produce healthier trees than isolated root zones.

 

SOIL VOLUME FOR TREES

 

• There’s a linear relationship between the soil volume required and the ultimate tree size.
• The ultimate tree size is defined by the project size of the crown and the diameter of the tree at breast height.  For example, a 16-in. diameter tree requires 1000 cu ft. of soil.

 

SOIL MODIFICATIONS

 

• To improve the soil’s ability to retain water and nutrients:
• Thoroughly till organic matter into the top 6 to 12 inches of most planting soils.  (Do not add organic matter to soil more than 12 in. deep).  Use composted bark, recycled yard waste, peat moss, or municipal processed sewage sludge.  All products should be composted to a dark color and be free of pieces with identifiable leaf or wood structure.  Recycled material should be tested for pH and certified free of toxic material by the supplier.  Avoid material with a pH higher than 7.5.
• Modify heavy clay or silt soils (more than 40% clay or silt) by adding composted pine bark (up to 30% by volume) and/or gypsum.  Coarse sand may be used if enough is added to bring the sand content to more than 60% of the total mix.
• Improve drainage in heavy soils by planting on raised mounds or beds and including subsurface drainage lines.
• Modify extremely sandy soils (more than 85% sand) by adding organic matter and/or dry, shredded clay loam up to 30% of the total mix.

 

SOIL VOLUME – REQUIREMENT FOR TREES

 

• Soil volume provided for trees in urban areas must be sufficient for long-term maintenance.
• There must be adequate drainage and room to grow for trees.

 

SOIL VOLUME – INTERCONNECTION

 

• The interconnection of soil volumes from tree to tree has been observed to improve the health and vigor of trees.

 

SOIL PROTECTION FROM COMPACTION OR DEGRADATION

 

• Coarse plantings keep pedestrians out of planters.
• Curbs protect planters from pedestrians and deicing salts.
• Underground steam lines must be insulated or vented to protect planter soil.

 

VISUALLY SYMMETRICAL TREES

 

• If visually symmetrical tree planting is required, symmetrical soil volumes are also required to produce trees of similar crown size.

 

TREE GUARDS

 

• Tree guards can protect young trees from trunk damage caused by bicycles.
• If made too small, however (less than 30 in. in diameter), they can damage the tree as it grows and are difficult to remove.
• The high cost and potential harm to trees outweigh the minor protection tree guards afford a trunk.
• They should be used only in areas with particularly high traffic.

 

SELECTING PLANTS FOR ROOFTOP PLANTING

 

• When choosing plants for a rooftop setting, consider the factors outlined here:
• WIND TOLERANCE: Higher elevations and exposure to wind can cause defoliation and increase the transpiration rate of plants.  High parapet walls with louvers can reduce wind velocity and provide shelter for plants.
• HIGH EVAPORATION RATE: The drying effects of wind and sun on the soil in a planter reduce soil moisture rapidly.  Irrigation, mulches, and moisture-holding soil additives (diatomaceous earth or organic matter) help reduce this moisture loss.
• RAPID SOIL TEMPERATURE FLUCTUATION: The variation in conduction capacity of planter materials results in a broad range of soil temperatures in planters of different materials.  Cold or heat can cause severe root damage in certain plant species.  Proper drainage helps alleviate this condition.
• TOPSOIL: Improve topsoil in planters to provide optimum growing conditions for the plants selected.  A general formula calls for adding fertilizer (determined by soil testing) and one part peat moss to five parts sandy loam topsoil.  More specific requirements for certain varieties of plants or grasses should be considered.
• ROOT CAPACITY: Choose plant species carefully, considering their adaptation to the size of the plant bed.  If species with shallow, fibrous roots are used instead of species with a coarse root system, consult with a nursery advisor.  Consider the ultimate maturity of the plant species when sizing a planter.

 

ROOFTOP PLANTING DETAILS

 

• There are five factors when designing rooftop planting:
• SOIL DEPTH: Minimum soil depth in a planter varies with the plant type: for large trees, the soil should be 37 inches deep or 6 inches deeper than the root ball; for small trees, 30 inches deep; for shrubs, 24 inches deep; and for lawns, 12 inches deep (10 in. if irrigated).
• SOIL VOLUME: To determine sufficient soil volume, refer to the linear relationship between soil volume and ultimate tree size (graph provided in text).
• SOIL WEIGHT: The saturated weight of normal soil mix ranges from 100 to 120 pcf, depending on soil type and compaction rate.  Soils can be made lighter by adding expanded shale or perlite.  Soils lighter than 80 pcf cannot provide structure adequate to support trees.
• DRAINAGE FABRIC: Plastic drainage material should be a minimum of ½ in. thick.  Most drainage material comes with a filter fabric attached, but the overlap joints provided are not wide enough for the unconsolidated soils found in planters.  A second layer of woven filter fabric, delivered in rolls greater than 10 ft. in width, should be installed.  Tuck the fabric over the exposed top of the drainage material to keep soil out of the drainage layer.
• INSULATION: Most planters do not require insulation; however, in colder climates planters with small soil volumes located over heated structures may require insulation.  Consult local sources for a list of cold-hardy plants.

PPP Notes - Landscaping

LANDSCAPING

 

IRRIGATION

 

• Irrigation system design considerations include the water supply, site conditions, climate, and plant material selection.
• The available volume of the water supply is measured in gallons per minute (gpm).
• The available pressure of the water supply is measured in pounds per square inch (psi).
• Water supply can be from a public or private utility system, or can be pumped from a well or pond.
• Selection of irrigation equipment and sizing of distribution piping is based on available volume and pressure of the water supply.
• Site conditions that must be considered are topography, drainage, soil type, and solar exposure.
• Important climatic conditions include predominant wind direction, annual rainfall, and temperature variations.
• When irrigation systems are subject to freezing temperatures, precaution against damage to the system components from freezing must be built into the design.
• Planting materials have different requirements for water.
• In fact, variations of turf grass may have vastly different watering needs.
• Plant water requirements include water lost by evaporation into the atmosphere from the soil and soil surface, and by transpiration, which is the water actually used by the plan.
• The combination of these is called evapotranspiration (ET).
• Because turf grass has the highest rate of ET of any planting materials in the landscape, and because the ET of turf varies depending on the seasons, irrigation systems are designed to replace water lost at the highest level of ET for the turf grass in the landscape.

 

IRRIGATION SYSTEM COMPONENTS

 

• There are a number of common irrigation system components, among them:
• Backflow Preventer: Prevents water from the irrigation system from backflowing into the potable water supply.
• Controller: Acts as a timer that maintains status of the day of the week and time of the day in order to activate electric control valves at a specific day, and duration.
• Main Line: The primary pipe supply line that distributes water from the point of connection of the source of supply to the electric control valve.  Main line piping of sizes 2.5” diameter and larger are typically class 200 PVC.  Piping of sizes 2 in. and smaller are typically schedule 40 PVC.
• Electric Control Valve: Low-voltage solenoid-actuated valves that control the flow of water from the main line into the lateral line piping.  Electric control valves are activated by the controller.  Signals are sent from the controller to the valves through direct burial wires.
• Lateral Line Piping: The pipe supply line that distributes water from an electric control valve to a sprinkler head or a drip emitter.  Depending on the application, lateral line piping can schedule 40 PVC, class 200 PVC, or class 160 PVC.  Lateral line piping for drip irrigation is typically polyethylene tube.
• Sprinkler Head: A water distribution device attached to the lateral line piping.  Rotary and impact sprinkler heads are used to irrigate large areas and can be spaced from 20 to 80 ft. o.c.  Popup spray sprinkler heads are used to irrigate smaller areas and can be spaced from 5 to 20 ft o.c.  Sprinkler heads are used to irrigate turf grass or broad areas of low-growing shrubs or ground covers.  For optimum efficiency, sprinkler heads are spaced to provide overlapping head-to-head coverage.
• Bubbler Head: A water-distribution device used to irrigate shrubs and ground covers by placing water immediately adjacent to the plant, or by flooding a planting bed.
• Drip Emitter: A water distribution device that distributes water very slowly, in increments measured in gallons per hour.  Drip emitters are used to water individual plants.

 

COORDINATION CONSIDERATIONS

 

• Check the contract to ascertain that an irrigation system is to be provided.
• On rare occasions, it is an option, which should have been determined when signing the contract.
• An irrigation plan should show:
• Limits of irrigation
• Approximate limits of grass versus shrub and ground cover areas
• Point of connection (POC) for the water
• Controller location
• Grading plan
• Any out-of-the ordinary conditions (e.g., underground obstructions, areas over structure, isolated planting areas, tree pits, or pots) with a note clarifying whether there areas are or are not to be irrigated
• Coordination with the plumbing engineer should occur near the start of the construction documents phase, mainly because the services needed to supply an irrigation system are the same as those for the domestic water system for a building.
• These include the location of the water meter and any calculations for the gallons per minute (gpm) and pounds per square inch (psi).
• When working on a project that has a water meter room within the building, it is wise to let the plumbing engineer know (even as early as the design development phase) that a backflow preventer and an irrigation meter separate from the domestic water meter will be needed.
• Ask the plumbing engineer to show the POC 2 ft. beyond the outside face of the exterior wall, or vault at a depth of 18 in. below finish grade and with a cap.
• This is particularly important for commercial jobs where meter room is below grade and the exterior wall is likely cast-in-place concrete. 
• If the irrigation main supply shows on the plumbing drawings, this will ensure the pipe is installed in the wall properly, with a waterstop, and has a tight seal around the pipe.
• There is no need for the water and electrical power sources to be located near each other; they only have to meet at the remote control valves.
• There needs to be a series of wires (one for each valve, plus a central wire) going through an exterior building wall 18 in. below grade or through the bottom of the pedestal, which has to be mounted on a concrete pad.
• These wires should always be enclosed in a “sleeve,” which is usually PVC.
• Once outside, the wires should remain encased in PVC pipe until they reach a mainline trench.
• From there they go off in all directions to the remote control valves, which should be buried under the pipe in the same trench.
• Irrigation sleeves should be installed prior to paving operations, but after final subgrade elevation has been established.
• The controller is best located in a place out of view from the general public.

PPP Notes - Retaining Walls

SITE DEVELOPMENT

 

RETAINING WALLS

 

• Retaining walls are designed and constructed to resist the thrust of the soil, which can cause the wall to fail by overturning, sliding or setting.
• In stone walls, resistance to soil thrust can be helped by battering the stonework (i.e. recessing or sloping the masonry back in successive courses).
• Garden-type retaining walls, usually no higher than 4 ft., are generally made from small building units of stone, masonry, or wood.
• For higher walls, reinforced concrete is more commonly used.
• Terracing may be built with walls of wood, stone, brick, or concrete.
• Walls less than 2 ft. high do not require drains or weepholes.
• Preservative-treated wood is recommended for any design in which wood comes in contact with the ground. 
• Redwood may be substituted if desired.
• Stagger vertical joints from course to course 6 in. minimum horizontally.  The thickness of the wall at any point should not be less than half the distance from that point to the top of the wall.

 

CAST-IN-PLACE CONCRETE RETAINING WALLS

 

• When designing cast-in-place concrete retaining walls, keep these guidelines in mind:
• Provide control and/or construction joints in concrete retaining walls approximately every 25 ft.  Every fourth control and/or construction joint should be an expansion joint.  Coated dowels should be used if average wall height on either side of a joint is different.
• Consult with a structural engineer for final design of all concrete retaining walls.
• Concrete keys may be required below retaining wall footing to prevent sliding in high walls and those built on moist clay.

PPP Notes - Exterior Stairs and Ramps

EXTERIOR STAIRS AND RAMPS

 

EXTERIOR STAIRS/RAMPS

 

• Throughout the centuries, stairs and ramps have been used to address elevation changes in the landscape.
• They can be heroic or modest, nuanced or straightforward, detailed or plain.
• They represent for designers opportunities to create delight, variety, viewpoints, and accents in the movement of people across a landscape.
• They are also zones for heightened access and safety consideration.
• This section leaves for the designer’s imagination the full potential of stairs and ramps as artistic design elements, and concentrates instead on access and safety design issues.

 

REGULATIONS

 

• Stairs and ramps as components of the pedestrian walkway system are regulated for minimum design standards at federal, state and local levels.
• With the ADA, the role of stairs and ramps in creating accessibility for all became a specific design focus.
• For designers, the first requirement is to thoroughly review the relevant jurisdiction’s accessibility and safety codes related to stairs and ramps.
• Any discrepancies between the information presented in this discussion and any regulation should always be resolved in the favor of the regulation.
• There are differences in the design requirements between local, state, and federal accessibility and safety regulations.
• Identifying and determining the relevant regulations for a project requires research and discussion with the project client.
• Private and local government projects usually must adhere to local, state, and federal requirements.
• State and federal projects usually exempt themselves from application of regulations enacted by lower jurisdictional levels.
• A review meeting early in the design process with the relevant building code enforcement group is advisable.  Determining the applicable regulations with the client is a professional liability responsibility of the design professional.

 

EXTERIOR VERSUS INTERIOR DESIGN STANDARDS

 

• Exterior stairs and ramps must deal with climatic issues that interior situations do not – obvious examples being rain and snow.
• In addition, the design and spatial variety of exterior landscape spaces make the location of stairs and ramps less predictable for pedestrians.
• Thus, in exterior design factors such as tread depth and slope, traction and detectable warning zones become important issues to consider.
• Directly applying interior stair and ramp standards to exterior locations is generally not a good practice.

 

EXTERIOR STAIR DETAILS

 

• A rule of thumb for tread depths and riser heights for exterior stairs can be translated to this equation:
• Height of Two Risers + Depth of One Tread = 26 Inches
• For exterior locations, a recommended range for risers is between 4 and 7 inches, with recommended tread depth of 12 and 18 inches.
• Stairs in exterior locations require a slope on the tread to shed rain and snow melt.  A generally recommended slope is a 2% slope from front to back of tread, or a ¼-in. on a 12-in.-wide tread.
• The leading edge of a step is called the step nose.
• Stairs nose details vary depending on the material used.
• Detailing of the stair nose is an important safety detail.
• The current accessibility standard is that step noses should have a radius of ½-in., with no overhang deeper than ½-in. on the step.
• The goal is to reduce the potential points where a person’s shoe could become trapped or tripped, such as a toe under a step overhang or a heel at a sharp nose edge.

 

CONSTRUCTION OF EXTERIOR STAIRS

 

• A construction concern for concrete stairs is the placement of reinforcing bars.
• Reinforcing steel should be placed a minimum of 3 in. back from any exposed surface of the step.
• Maintaining a minimum 3-in. clearance reduces the potential for breakup of the step due to differential freeze/thaw expansion between the reinforcing steel and the concrete.  This is especially important in the stair nose zone.
• Adding slip dowels and keyed joints at the top of concrete stairs to adjacent concrete paving or subsurface layers is a good construction detail, to avoid differential settlement and tripping hazards.
• The bottom step footing on concrete stairs or concrete subsurface for stairs should extend down, at a minimum, to the local freeze depth.
• Manufactured metal stair nosings are sometimes used in heavily trafficked locations to reduce the wear and tear on step noses.
• In climates with freezing temperatures, selecting a product and installation method that accounts for deferential freeze/thaw effects between the metal and the step material is important.
• Metal stairs in exterior locations should be built with open-mesh metal grating or with embossed or raised patterning on the tread surface, to provide traction and the ability to release rain or snow quickly from the surface of the step.
• When open-mesh metal materials are used on steps, the rule of ¼-in. maximum clear opening to provide safety for shoe heels is a good safety standard to follow.
• Exterior raised steps made with wood, plastics or composites do not require a tread slope if there is a ¼-in. to ½-in. gap between each wood member.
• This gap helps to release rain and snow buildup that can cause slipperiness.
• For timber steps that are laid on grade, selecting wood varieties and installation methods that resist moisture rot is important to achieve long-term durability.
• Cedar, redwood, and preservative treated woods are generally considered reliable selections for ground-laid timber steps.
• Gravel subsurface is often used in high-moisture environments to reduce the moisture buildup beneath ground-laid timber steps.
• Stone, when used in ground-laid steps, should be selected for flat tops and be large enough so that they do not overturn when pressure is applied at the step nose. 
• Lapping each stone step by approximately one-fourth to one-third of their tread depth helps to prevent this overturning.
• If laid with spacing between each stone step, each stone should be buried up to one-third the thickness of the stone, and be level on its top surface.
• Gravel beds or designed structural soil mixes such as base course should be considered whenever high moisture content or poor structural soil conditions exist.
• A solid subsurface contributes to the long-term durability and stability of a set of steps.

 

EXTERIOR STAIR RUNS, WIDTHS, AND LANDINGS

 

• Single steps should be avoided, as they create a tripping hazard because of their lack of visibility. 
• Stairs and steps in general should be distinguished from surround paving by a difference in material, color, or pattern, to highlight and make them more prominent. 
• In most jurisdictions, when there are more than three steps, handrails must be provided.
• As a general rule, exterior stair landings should, at a minimum, match the width of the stairs and be a minimum of 3 ft. deep.
• Exterior stairs when located at main entries or emergency exits of buildings should, at a minimum, be the width of the exiting doorways.  This helps to maintain a safe emergency egress zone.
• Providing a landing at doorways and gates that are served by stairs makes using doorways safer and more convenient.
• The swing of the door should be accounted for in scaling the depth of a landing, to avoid having to be on a step to open or close a door or gate.
• Installing intermediate stair landings where an elevation change of between 2.5 and 5 ft. has been reached on a run of stairs creates a comfortable resting place for users.
• When longer runs of stairs are used consideration for larger landings with opportunities for sitting should be given.
• Landings should be built with a minimum 2% slope toward the downhill edge.

 

RAMPS

 

• Accessible ramp slope standards initially were based on research using disabled adult males as the test population.  This means that, perhaps, it is not the best standard for the elderly, children, or the frail.
• Thus, for the greatest universal access of a project, designers should target for the lowest ramp slope rate practical.
• Research based on the elderly and children is beginning to show that a better slope rate for those populations is 1:16 or lower.
• The 1:12 or 8.333% slope rate should be considered the maximum rate, not the goal.
• As a practical cost consideration, any ramp that is flatter than 1:20 does not require handrails and, thus, can avoid that cost.

 

STREET RAMPS

 

• There are two common locations for exterior ramps: at street corners and crossings, and where grade changes occur. 
• The design of street ramps is highly regulated by local, state, and federal ordinances.
• This discussion does not provide street ramp standards because the design requirements are diverse and undergo frequent review and modification.
• Thus, for street ramp standards, the design professional is referred directly to the relevant ordinance determined by discussion with the relevant code enforcement agency and the client.

 

EXTERIOR RAMP DETAILS

 

• The most important design feature of an exterior ramp is the surface of the ramp.  Ensuring that it is not slick in wet weather is critical for safety.
• Follow these guidelines:
• On concrete ramps, the surface should be, at minimum, a medium broom finish, with the brook strokes being perpendicular to the flow of traffic.
• Stone clad ramp designs should consider honed or scored surfaces, and avoid any smooth, flat finish.
• Metal ramps designs should consider structural grille/grate panels or embossed or patterned metal, and avoid any smooth finish.
• Installing slip dowels or keyed joints at the tops and bottoms of ramps to adjacent paving helps to avoid differential movement that causes tripping hazards at the entries to the ramp.

 

RAMP WIDTHS AND LANDINGS

 

• Design guidelines for ramp widths and landings are as follows:
• An accessible ramp should have a clearance between ramp handrails of at least 36”, to allow a person in a wheelchair room for his or her hands to turn the wheels.
• A ramp landing should occur at a maximum of 30 ft. of run of a ramp.  The ramp landing must be a minimum of 60 in. clear depth.
• If ramps change direction at landings, the minimum landing size must be 60 in. by 60 in.
• If an exterior doorway is located at a ramp landing, the landing must comply with safety and access requirements for the door.

 

STAIRS AND RAMPS HANDRAILS

 

• As part of the accessible system, stair and ramp handrails are covered under access and safety regulations.  Their placement, height, length, strength, and safety details fall under the design guidance of these regulations.
• Thus, familiarity with the relevant codes is paramount.
• General requirements for all handrails are:
• The top of handrail to stair nose or ramp surface distance should be constant – a height between 34 and 38 in.
• The diameter of width of the handrail must be 1-1/4 in. to 1-1/2 in.
• Structurally, the handrail must be able to withstand 250 lb. of downward pressure per inch.
• The ends of handrails should not be sharp at the ends.
• General standards for stair handrails are:
• At the top of the stair run, the rail must be level for 12 in. before the first step nose.
• At the bottom of the stair run, the rail must extend for one tread length at the same slope as over the majority of the stairs, then remain level for an additional 12 in.
• General standards for ramp handrails are:
• At the top of the ramp, the rail must be level for 12 in. before the top of the ramp.
• At the bottom of the ramp, the rail must remain level for 12 in., beyond the end of the ramp.