Grading the Home- Wenatchee and Chelan Home Inspection
One thing that has struck me during home inspections is how often many of the cement (or asphalt) appurtenances can be installed in a manner that will cause issue with the home.
This could include sidewalks/walkways or patios poured over the top of siding materials or more importantly when these components are installed in such a manner to create a negative or flat grade around the home.
During the home inspection I will be looking for staining from pooling and other evidence of improper drainage.
Your home should always have grading designed in such a way to carry water away from the structure and foundation walls. The IRC codes suggest the grade should be a minimum of 6 inches within the first 10 feet away from the home for soils. In addition ASCE (American Society of Civil Engineers) 7.35 suggest that ground surface swales parallel to the house walls (rear yard and both side yards) shall have longitudinal slopes of at least 2% (6” per 25′) if practical, and 1% (3” per 25’) minimum.
What about the grade for concrete, brick or asphalt surfaces? This is less defined.
A surprising amount of water can infiltrate the surface of these materials. FHWA (Federal Highway Admin.) studies show typical moisture infiltration rates for asphalt is around 33% - 50% and for concrete it is around 50% - 67%.
Again ASCE 7.35 suggests concrete or hardscape surfaces that may allow water to flow towards the foundation system perimeter should be modified to direct water away from the foundation perimeter. Gaps between concrete surfaces along the foundation system perimeter that allow surface water to infiltrate into the foundation bearing soils should be eliminated.
Generally accepted grading for these types of surfaces is 1/8 to 1/4 inch per foot (the more the better). If you do not have a proper grade on these surfaces water can collect and can lead to moisture accumulation at the foundation.
Here we have an example of a negative grade at the walkway. This looks innocent enough.
Here we see the effects of the water accumulation at this area. Water is traveling down the foundation wall and under the footing and resurfacing in the crawlspace. Over time this can lead to undermining of the footing.
Remember when any cement, pavers or asphalt surfaces are to be installed the contractor should properly plan for drainage from these surfaces.
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NCW Home Inspections, LLC is a Licensed Washington State Home Inspection service located in Wenatchee Washington serving Chelan County, Douglas County, Kittitas County, Okanogan County and Grant County Washington and the cities of Wenatchee, Leavenworth, Cashmere, Orville, Cle Elum, East Wenatchee, Quincy and many more…
Your Wenatchee and Chelan Professional Home and Structural Pest Inspection Service
509-670-9572 or on the web atwww.ncwhomeinspections.com
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