Alternative Building Materials Sd 21
Alternative Building Materials
SD-21
Design Objectives
Maximize Infiltration
Provide Retention
Source Control
Minimize Impervious Land
Coverage
Prohibit Dumping of Improper
Materials
Contain Pollutant
Collect and Convey
Description
Alternative building materials are selected instead of conventional materials for new
construction and renovation. These materials reduce potential sources of pollutants in
stormwater runoff by eliminating compounds that can leach into runoff, reducing the need for
pesticide application, reducing the need for painting and other maintenance, or by reducing the
volume of runoff.
Approach
Alternative building materials are available for use as lumber for decking, roofing materials,
home siding, and paving for driveways, decks, and sidewalks.
Suitable Applications
Appropriate applications include residential, commercial and industrial areas planned for
development or redevelopment.
Design Considerations
Designing New Installations
Decking
One of the most common materials for construction of decks and other outdoor construction has
traditionally been pressure treated wood, which is now being phased out. The standard
treatment is called CCA, for chromated copper arsenate. The key ingredients are arsenic (which
kills termites, carpenter ants and other insects), copper (which
kills the fungi that cause wood to rot) and chromium (which reacts
with the other ingredients to bind them to the wood). The amount
of arsenic is far from trivial. A deck just 8 feet x 10 feet contains
more than 1 1/3 pounds of this highly potent poison. Replacement
materials include a new type of pressure treated wood, plastic and
composite lumber.
January 2003
California Stormwater BMP Handbook
1 of 3
New Development and Redevelopment
www.cabmphandbook.com
SD-21
Alternative Building Materials
There are currently over 20 products in the market consisting of plastic or plastic-wood
composites. Plastic lumber is made from 100% recycled plastic, # 2 HDPE and polyethylene
plastic milk jugs and soap bottles. Plastic-wood composites are a combination of plastic and
wood fibers or sawdust. These materials are a long lasting exterior weather, insect, and chemical
resistant wood lumber replacement for non structural applications. Use it for decks, docks,
raised garden beds and planter boxes, pallets, hand railings, outdoor furniture, animal pens,
boat decks, etc.
New pressure treated wood uses a much safer recipe, ACQ, which stands for ammoniacal copper
quartenary. It contains no arsenic and no chromium. Yet the American Wood Preservers
Association has found it to be just as effective as the standard formula. ACQ is common in Japan
and Europe.
Roofing
Several studies have indicated that metal used as roofing material, flashing, or gutters can leach
metals into the environment. The leaching occurs because rainfall is slightly acidic and slowly
dissolved the exposed metals. Common traditional applications include copper sheathing and
galvanized (zinc) gutters.
Coated metal products are available for both roofing and gutter applications. These products
eliminate contact of bare metal with rainfall, eliminating one source of metals in runoff. There
are also roofing materials made of recycled rubber and plastic that resemble traditional
materials.
A less traditional approach is the use of green roofs. These roofs are not just green, they're alive.
Planted with grasses and succulents, low- profile green roofs reduce the urban heat island effect,
stormwater runoff, and cooling costs, while providing wildlife habitat and a connection to nature
for building occupants. These roofs are widely used on industrial facilities in Europe and have
been established as experimental installations in several locations in the US, including Portland,
Oregon. Their feasibility is questionable in areas of California with prolonged, dry, hot weather.
Paved Areas
Traditionally, concrete is used for construction of patios, sidewalks, and driveways. Although it
is non-toxic, these paved areas reduce stormwater infiltration and increase the volume and rate
of runoff. This increase in the amount of runoff is the leading cause of stream channel
degradation in urban areas.
There are a number of alternative materials that can be used in these applications, including
porous concrete and asphalt, modular blocks, and crushed granite. These materials, especially
modular paving blocks, are widely available and a well established method to reduce stormwater
runoff.
Building Siding
Wood siding is commonly used on the exterior of residential construction. This material
weathers fairly rapidly and requires repeated painting to prevent rotting. Alternative “new”
products for this application include cement-fiber and vinyl. Cement-fiber siding is a masonry
product made from Portland cement, sand, and cellulose and will not burn, cup, swell, or
shrink.
2 of 3
California Stormwater BMP Handbook
January 2003
New Development and Redevelopment
www.cabmphandbook.com
Alternative Building Materials
SD-21
Pesticide Reduction
A common use of powerful pesticides is for the control of termites. Chlordane was used for many
years for this purpose and is now found in urban streams and lakes nationwide. There are a
number of physical barriers that can be installed during construction to help reduce the use of
pesticides.
Sand barriers for subterranean termites are a physical deterrent because the termites cannot
tunnel through it. Sand barriers can be applied in crawl spaces under pier and beam
foundations, under slab foundations, and between the foundation and concrete porches,
terraces, patios and steps. Other possible locations include under fence posts, underground
electrical cables, water and gas lines, telephone and electrical poles, inside hollow tile cells and
against retaining walls.
Metal termite shields are physical barriers to termites which prevent them from building
invisible tunnels. In reality, metal shields function as a helpful termite detection device, forcing
them to build tunnels on the outside of the shields which are easily seen. Metal termite shields
also help prevent dampness from wicking to adjoining wood members which can result in rot,
thus making the material more attractive to termites and other pests. Metal flashing and metal
plates can also be used as a barrier between piers and beams of structures such as decks, which
are particularly vulnerable to termite attack.
Redeveloping Existing Installations
Various jurisdictional stormwater management and mitigation plans (SUSMP, WQMP, etc.)
define “redevelopment” in terms of amounts of additional impervious area, increases in gross
floor area and/or exterior construction, and land disturbing activities with structural or
impervious surfaces. The definition of “redevelopment” must be consulted to determine
whether or not the requirements for new development apply to areas intended for
redevelopment. If the definition applies, the steps outlined under “designing new installations”
above should be followed.
Other Resources
There are no good, independent, comprehensive sources of information on alternative building
materials for use in minimizing the impacts of stormwater runoff. Most websites or other
references to “green” or “alternative” building materials focus on indoor applications, such as
formaldehyde free plywood and low VOC paints, carpets, and pads. Some supplemental
information on alternative materials is available from the manufacturers.
Fires are a source of concern in many areas of California. Information on the flammability of
alternative decking materials is available from the University of California Forest Product
Laboratory (UCFPL) website at: http://www.ucfpl.ucop.edu/WDDeckIntro.htm
January 2003
California Stormwater BMP Handbook
3 of 3
New Development and Redevelopment
www.cabmphandbook.com
