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RED53 08-17-2008 04:41 PM

Insulating under shower drain
We are in the process of installing a 3 piece shower stall. When the drain cover is not in place, and you look into the drain, you can also see the "light of day" of our crawl space. Shouldn't we insulate this area (seems we would get alot of cold air up thru this area) ? If so, how do we do it and with what? Hope this makes sense- I'm just the wife whose intuition and common sense forsees a potential problem here! Thanks!

wire_twister 08-17-2008 05:48 PM

Insulate from inside the crawlspace with fiberglass insulation. Do not pack the insulation tight just cover the space loosely.

Marlin 08-17-2008 08:49 PM

What kind of drain do you have that you can see light through without the cover on it?

buletbob 08-17-2008 08:51 PM


Originally Posted by wire_twister (Post 149437)
Insulate from inside the crawlspace with fiberglass insulation. Do not pack the insulation tight just cover the space loosely.

I agree. BOB

Piedmont 08-18-2008 09:03 AM

I plug every plumbing fixture penetration with expanding foam sealant, I'll take the opposite view and say fiberglass isn't the way to go. It is terrible at stopping air flow, and shouldn't be for sealing air leaks and in a moist environment is particularly a bad choice it turns into a mold/mildew breeding ground. I think stuffing it with fiberglass just isn't the way to go, it doesn't stop air flow, and with cold air flowing through it moisture can condense and I think installed at your shower drain attempting to stop air flow, instead you will create an environment for mold/mildew.

I would use expanding sealant around the floor penetraion (not shower drain) and let it expand and seal. Practice with it if you've not used it before it will expand about 3x-4x larger than when you first apply so leave it room to expand or if there isn't much room only use a small bead. If you judge wrong and it doesn't expand enough to seal the opening, you can always apply it again to finish the job which is much better than putting too much, which causes it to expand uncontrollably out every crack and it will just keep coming... it's better to be safe than sorry and put too little and another application if necessary. The cans have to be used upside down, nail polish remover can remove accidents while still wet but once dry it requires elbow grease. If possible try to seal the floor penetration from below to minimize it interfering with your shower drain. Expanding sealant is approved for wet conditions, impossible for mold/mildew to grow, and for sealing air leaks so it's the right tool for the job however it's also permanent as it dries solid and sticky as crazy glue the only way to remove it once dry is with a razor/knife.

RED53 08-18-2008 03:40 PM

Thanks for help!
Thanks for all the replies to my question. Marlin, in regards to your question about the drain - the hole around the drain pipe is a little larger than the drain itself and its around the drainpipe that I can see the light of the crawlspace. Does that make sense?!? I think I've found a new best friend in DYI - I've always got a question about home repair!!!

buletbob 08-18-2008 03:48 PM

the code here on the island requires all holes that are drilled between floors walls from basement to first floor on up to second floor ceiling. must be caulked with an approved fire caulk. so here sealing with insulation would of been norm. I do agree with the expanding foam idea makes sense, but here we couldn't,t get away with it. I hope the OP can take advantage to using it, that would be the way to go. Good Luck. BOB

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