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Community and Q&A

Waterproofing slab to wood sill?

Florida Homeowner | Posted in General Questions on

Good Morning!

I am closing in a four wall external (element exposed) area. The area already had a slab and the back all that was exposed was not in great condition. I demo’d the back wall and rebuilt it (picture attached) and roofed the area (there was no roof prior, just stucco). The slab for the house is 4 inches higher than the slab for the room that I am building. Both are above grade. I am going to stucco the external wall that is in the picture. My question is how do I water proof the outside joint where the slab meet the wood sill as a precaution? I was think to use a liquid rubber membrane and then cover that with a window flashing. The than the stucco would go over both. We are expecting an addition so the family and this area will be the nursery off our bedroom. I just want to make sure I do not run in to additional issues in the future. Thanks for any help/suggestions provided.

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  1. GBA Editor
    Martin Holladay | | #1

    Your detail will look something like the detail shown below. You need to seal the crack between your mudsill (bottom plate) and the concrete with foam sill-seal. This also provides a capillary break. You can improve the airtightness of this crack by installing a bead of silicone caulk on one or both sides of the crack.


  2. GBA Editor
    Martin Holladay | | #2

    Here is another weep screed detail. I think that the bottom of the weep screed should ideally be 6 or 8 inches above grade, but that isn't always possible.


    1. AlainDiaz | | #3

      Martin Holladay, could you tell me where did you get that detail?
      Thank you.

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