Replies

1. GBA Editor
   Martin Holladay | Dec 04, 2016 04:26am | #1

   David,
   For a new house, the best way to seal this seam is with caulk or a gasket before the drywall is installed. But it's too late for that. (If you build another house, you might be interested in learning how this is done. This article will describe the best approach: Airtight Drywall.)

   Assuming the baseboard has not been installed, you want to clean up the area very thoroughly with a vacuum cleaner, and the seal the gap between the drywall and the subfloor with caulk or (if the gap is wide) with canned spray foam.

2. 
   schreibdave15 | Dec 04, 2016 07:11am | #2

   Thanks Martin. This is a tract home and getting the builder to get his subs to do any air sealing that is out of the ordinary is very hard - even when I am willing to pay extra for the time and materials necessary to do it in the ways described in your attachment. So I pick my battles and I come in at night and on weekends (without permission) and foam and caulk what I can. I have been following behind the sheet rock guys for 3 days now. They think I am nuts but I feed them, so ...

   I paid extra to have spray foam spayed around the baffles and in the narrow gaps in the framing. The installer apparently didnt understand what his assignment was because he got foam all over the place but very little in the areas where I needed it. To add insult to injury he had to rip out the already installed fiberglass to get at those locations and after spraying 2" of foam in the cavity he threw out the FG leaving 3.5" of empty space - space that could just as easily have been stuffed with the FG that was lying at his feet - and that I had already paid for.

   When I bring up air sealing these are the kinds of answers I get: 1- "I didnt do that in MY house", 2- "this is the way we always do it." 3- "how is that outlet going to leak air? It will be covered by a ($.39 plastic) receptacle cover", etc etc

   Sorry for the rant. Back to my question. It is really tough to get either foam or caulk up into that tight area where the sheetrock comes down over the bottom plate. The angle is impossible, you cant see the gap and neither caulk nor foam really want to adhere to the 1/2 of exposed, dusty SR. That's what made me think that a continuous strip of quality tape would work best. I would vacuum the dust out of that crevice and then carefully apply 2" tape so that it covers maybe 1/2" of the face of the drywall and then is adhered tightly to the bottom plate. What do you think? I have a foam gun so the fastest, easiest and cheapest way to do it would be with foam but I am not convinced that the foam will get into that important crevice between the back of the SR and the face of the bottom plate.

   Thanks again

3. GBA Editor
   Martin Holladay | Dec 04, 2016 12:14pm | #3

   David,
   At this point, it's easier to seal the drywall to the subfloor than it is to seal the drywall to the bottom plate.