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Foundation Waterproofing and Drainage
For the Northwest Environment


The potential drainage problems you may encounter in the rainy Pacific Northwest depend on your particular soils. While sandy soil doesn't pose much threat, much of the Puget Sound region is composed of clay-based soil which can be more problematic. In order to avoid a wet crawl space, leaky basement or soggy yard, foundation drainage issues need to be handled correctly.

PVC Drainage Piping

We specify rigid 4" PVC perforated pipe with glued joints. This is in lieu of the soft black "slinky" drain pipe which is prone to getting crushed and cannot be Roto-Rooted. Downspouts should all lead to a drain tile system composed of 4" rigid PVC pipes with glued joints. This system should be totally separate from the footing drains.

Use a Waterproof Coating

Foundation walls for crawl spaces (including the top of the footings) should be coated with asphalt emulsion at the very least, and with a membrane if they are over 48" tall. Basement walls should always be coated with a waterproof membrane, not just asphalt emulsion. In addition to the membrane, drainage matt should be installed against the wall to guide the water down to the footing drains.

485 Rainier Blvd North, suite 103 Issaquah, WA 98027 .. Tel: 425 - 557 - 3774 .. Fax: 425 - 557 - 3760 .. info@merrilldesign.net