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Re: Waterproofing and Sealing Sill Plates on Concrete Slab

From: rkymtndepass@yahoo.com
Category: Drainage/Waterproofing
Remote Name: 71.37.87.128
Date: 02 Dec 2005
Time: 11:52 AM

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Question: How do you waterproof or seal a sill plate on a concrete slab as well as the wall sheeting that attaches to it?

Builders Websource Answer®: Several companies manufacture products specifically to seal / moisture-proof sill plates that come in contact with concrete slabs and foundations. The sill sealers are generally made from compressible polyethylene foam that you install between the foundation and the sill plate, creating a air-tight membrane that also helps to keep the sill plate from rotting. Available in 25' - 82' rolls, sill sealer or seal gasket comes in various widths depending on the sill plate. Typical sizes include 3.5 (for 2x4 sill plates), 5.5 (for 2x6 sill plates), 7.5 (for 2x8 sill plates), and 9.5" (for 2x10 sill plates). You can also use the larger widths with 2x4 or 2x6 sill plates by wrapping the excess up over the base of the exterior wood sheathing. In this case, to prevent moisture from creeping into the base of the sill plate, be sure that any external vapor barrier, such as stucco paper or building wrap, laps over the top of the edge of the sill wrap and continues all the way down to the weep screed (placed typically just below the cold joint between the foundation and the sill plate).

One reputable manufacturer, PROTECTO WRAP, offers a range of sill sealer products. According to the company's webiste, "Protecto Premium Energy Sill Sealer combines a full 3/8” closed cell polyethylene foam with an aggressive self adhesive waterproofing membrane that conforms and seals off the voids and irregularities between the top of the foundations and sill plate." An even better product is Protecto Triple Guard. "Triple Guard’s triple protection adheres to the face of the foundation, adheres to the top of the foundation wall, and adheres to the face of the sill plate/skirt board, totally sealing off the cold joint between the foundation and frame construction," according to the company. Benefits of products such as Protecto Triple Guard include:

• Reduced energy costs
• Fewer builder call-backs
• 50% more protection from energy loss compared to 1/4" sill sealers
• Self adhering for easy installation
• Mitigates moisture damage and sill plate rot
• Adapts to foundation irregularities to prevent air and insect infiltration
• Approved for residential and commercial installation

The following table compares similar products from several manufacturers:

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