b'YOUR TOOLKIT FOR BUILDING EXCELLENCEcontinued from page: 22designed and installed foundation drainage system cansee if rainwater can easily enter the foundation drainage system.lower the elevation of a water table.The water table canSoil moisture exists in soil even when all subsurface water be lowered because the foundation drains allow subsurfacehas been drained out of the soil.Capillary water in the soil water to drain out of the soil around the building foundation.can often cause moisture problems inside building spaces Theresultingsubsurfacewaterfreezoneprovidesathat are in contact with the soil when building foundation place for a building foundation to exist without beingcomponents are not protected from soil moisture.The impacted by subsurface water in contact with buildingspecific details for protecting a building foundation from foundation.The ability of a foundation drainage systemsoil moisture varies depending upon building foundation to lower a water table is discussed in more detail in theconstruction system.The two publications mentioned APA Build a Better Home: Foundations publication.earlier provide detailed discussions and diagrams on how A post-frame building foundation can be protected fromto protect different foundations from soil moisture.In subsurface water using a foundation drainage system if ageneral, gravel (often 3/4 diameter) or damp proofing high-water table is found on a post-frame building site.Themethodsprovideacapillarybreakprotectingthe drainage system must be placed outside (typically 2 or more)foundation from capillary moisture movement.A vapor of the post foundations and at a lower elevation than the bottombarrier, often polyethylene film, minimizes moisture of the post foundation pads.The installation of a foundationvapor movement from the soil into the building space.drainage system must not impact the post foundations. The post foundations of a post-frame building need to beProtecting the exterior building envelope kept subsurface water free to minimize frost heave issues. from moistureSurface water that infiltrates into the soil becomes subsurfaceIndoor moisture sources can be the cause of many types water.The key is to minimize surface water infiltrationof building moisture problems.Two solution aspects near a building.As discussed in part two of this series,need to be addressed with respect to indoor moisturegood site drainage must be established so surface waterprotecting the exterior building envelope and removing drains away from building. However, foundation drainexcessmoisturewithventilation.Thisfourthpart systems need to be protected from surface water infiltrationfocuses on protecting the building exterior envelope.flooding.Many foundation resources will show the need forWhere a building is located impacts how to properly protect granular backfill or gravel to be placed against a basementexterior walls and insulated ceiling assemblies from moisture foundation wall, especially on building sites with clay and/orproblems.Different climate zones have been established highly expansive soils.The granular or gravel backfill helpsfor the US as shown in Figure 3.The specific design and protect the foundation wall from high soil pressures whenconstruction details vary depending upon where your soils expand during wet periods.A low permeability soilbuilding is located.The climate map shown in Figure 3 needs to be placed at least 6 to 8continued on page 24inches think to minimize surface water infiltration directly intoFigure 3Climate Zone Map from DOE and USEPA.the granular or gravel backfill. If the granular backfill is installed from the drainage system to the top of the finish grade around a building, rainwater is likely to drain directly into the gravel backfill especially during heavy and extended rainfall events. When rainfall directly enters a foundation drainage system, the drainage system typically becomes flooded because the typical 4 perforated drainage pipe is not nearly large enough to serve as a storm water drainage system.If a building basement with a basement foundation often becomes wet during heavy or extended rainfall periods, check to continued on page: 23 FRAME BUILDER - NOV2023 / 23'