Checklist: Achieving Durability in Buildings: A Checklist for Action
Survey site to assess moisture and drainage conditions.
Potential moisture problems on a site may be identified by examining soils, surface water flows, drainage conditions, and existing vegetation. An understanding of site conditions will inform drainage strategies and other design features.Grade site to drain water away from building.
Grade the ground away from the building at a minimum of 4% (1/2" per 12" or 4 cm/m) for at least 6' (2 m) out from the foundation. With paved surfaces against the building (patios, sidewalks, driveways), grade at a minimum of 2%.Provide gutters and downspouts.
Use gutters and downspouts to capture rainwater falling on the roof and carry it away from the building.Provide foundation waterproofing or dampproofing and drainage.
Treat the outside of foundation walls with spray-on or trowel-on waterproofing in wet sites and dampproofing in drier sites. Provide a free-draining layer against the foundation and footing drains at the base of the wall that drain to daylight or sumps.Protect foundation walls from frost heaving.
Insulate the exterior of the foundation or the ground outside the foundation (shallow frost-protected foundation) to prevent frost heaving and the development of cracks that can become pathways for moisture.Provide capillary break on foundation components.
Apply a capillary break on top of the footing before pouring or laying the foundation walls, and on top of the foundation walls before framing the building.Provide adequate roof overhangs.
Protect building walls from rain with roof overhangs on both eaves and rakes. A minimum 12" (30 cm) overhang is recommended in climates with more than 20" (50 cm) of rain annually, with the recommended overhang increasing to 18" (450 cm) with over 40" (100 cm) of rain per year.Provide drainage plane (rain screen) in walls.
Provide a drainage plane or rainscreen detail in walls to reduce moisture problems and prolong the life of exterior finishes. With wood siding, provide an airspace on the outside of the sheathing and any housewrap using strapping perpendicular to the siding.Follow recommended practice for vapor barriers, air barriers, and vapor retarders.
Recommendations on vapor barriers and vapor diffusion retarders have changed dramatically in recent decades. Most building scientists today recommend concentrating on air barriers and avoiding a separate vapor barrier in all but the coldest climates so that the wall cavity can dry to the interior or exterior.Provide proper flashing.
Proper flashing details are critical in controlling moisture entry into buildings. Make sure that flashing is properly lapped to shed rain.Rely on caulks and sealants only where repairs are possible.
Caulks and sealants generally have short lifespans and need to be reapplied periodically; rely on them only in locations where they can be reapplied fairly easily.Ventilate roofs in most situations.
While hot roofs have been used very successfully, most building science experts still recommend vented roofs in most situations so that any accumulated moisture can be vented.Do not ventilate crawl spaces.
Most building science experts today recommend against venting crawl spaces and unheated basements. Block moisture entry into the crawl space or basement with a capillary break, such as a layer of polyethylene on the ground or beneath the concrete slab.Keep wood away from ground contact.
To prevent decay and obviate the need for treated wood, choose non-wood materials where ground contact or splash-back is possible.Use treated wood where ground contact or splash is expected.
Where ground contact or splash-back is possible, use wood that has been treated to prevent decay. Use the least-toxic treated wood option that will serve the needs. See, for example, EBN Vol. 13, No. 10.Specify high-performance windows or glazings.
Use windows and glazings with high R-value (low U-factor). These will reduce condensation problems, which can lead to rot and other durability problems.Protect building materials from weather on the job site.
Fully protect all building materials from rain to avoid introducing mold or shortening the useful life of those materials.Pressure-test plumbing for leaks.
After plumbing a building, pressure-test to ensure that there are no leaks. Leaking pipes are one of the leading causes of mold and decay in buildings.Protect against leaking clothes washers.
Burst clothes-washer hoses are one of the leading causes of insurance claims in houses. Use only quality hoses, instruct homeowners to replace hoses periodically, and position the washer on a drainage basin large enough to capture at least the volume of water in the tub.Insulate cold-water pipes.
Cold-water pipes in certain climates are a source of condensation and moisture damage. Insulate pipes to eliminate this problem.Ventilate all bathrooms and kitchens.
Bathrooms and kitchens are the leading sources of moisture in most houses. Vent both to the exterior with quiet spot fans or a central ventilation system. Low noise is important so that occupants will use the fans.Install entryway track-off matting.
Significant moisture is carried into buildings on occupants’ feet. Install track-off entryway systems to capture this moisture. See EBN Vol. 10, No. 10.Heat and Sunlight
Specify reflective roofing.
Use reflective roofing to keep the surface temperature down, which will prolong the life of both the roofing and the substrate. Reflective roofing is most widely available for low-slope roofs, but reflective pitched roof options are also available.Consider a green roof.
With a low-slope roof, as on most commercial buildings, consider a green (vegetated) roof to extend the life of the roof membrane. See EBN Vol. 10, No. 11.Specify light-colored exterior wall finishes.
Use light-colored wall surfaces (as with roofs) to keep surface temperatures lower and prolong the life of coatings and siding materials.Specify overhangs above south windows.
Sunlight will degrade certain interior finishes and furniture. Use overhangs above windows to help block sunlight during the summer months. Note that the benefits of sunlight penetration (such as passive solar heating and daylighting) may outweigh the drawbacks.Specify UV-protective glazings as needed.
To protect interior finish materials and furnishings, specify glazings that block the most destructive ultraviolet radiation.Specify UV-resistant materials.
For outdoor exposure, use materials that are UV-resistant or protected from the sun. Plastics used outdoors, for example, should include UV inhibitors. Interior materials, such as fabrics, should be fade-resistant if used in rooms with significant solar gain.Provide vegetative shading.
To protect buildings from excessive heat and sun, plant trees, vines, and other vegetation. See “Cooling Load Avoidance Strategies” in EBN Vol. 3, No. 3.Ozone and Acid Rain
Avoid susceptible materials in high-pollution regions.
In areas with significant smog or acid rain, avoid roofing and other exterior finishes that are susceptible to damage from these pollutants.Insects
Provide physical termite barriers.
In areas with risk of termites, install termite shields to block the entry of subterranean termites into buildings. Instruct building owners on inspection of termite shields. Other products, such as TermiMesh™ and termite-barrier sand, provide additional protection. See EBN Vol. 9, No. 9.Provide insect-resistant materialsas needed.
In areas where termite damage is common, provide wood treated with borates or sodium silicate (such as TimberSil™) for structural framing members, or consider use of steel framing.Provide termite bait treatment where needed.
In areas with known termite problems, recommend the use of termite-bait systems (rather than blanket insecticide treatments) to protect wood materials.Prevent vegetation from contacting building.
To minimize insect entry, provide at least some separation between the building and vegetation, such as shrubs and trees.Material Selection – General
Keep shortest-life materials most accessible.
Design building assemblies so that the least durable components are most accessible.Choose durable materials and products.
When choosing between comparable-function materials, choose the more durable. Spending more on longer-lasting materials and products is often justified.Provide guidance on maintenance requirements.
Provide building occupants with specific information on the maintenance of materials and products to ensure long life.
