Hello everyone, first time fine homebuilding forum poster here and I’m hoping someone can give me some sound guidance. I’m looking to seal up a very large gap in my NYC apartment, for both insulation/pest management purposes. Looking around my space recently I discovered in the main living area about a 3/4″-1″ wide gap behind the steam pipe in the corner (I think that’s what that pipe is called), that runs just about the entire length of the window trim next to it. From the front the gap is not noticeable as the window trim seems to butt right against the steam pipe. The pipe is also only a few inches away from the abutting wall so it’s not really a place one ever tends to go looking behind, but I can not unsee what I have discovered.
Initially I considered milling up a strip of wood to stick in the gap but the wall is very irregular and at one point goes over some moulding, scribing the strip would be next to impossible given the gap’s location. I then thought a polyurethane foam sealant could do the trick but have concerns about spraying that stuff directly on the backside of the steam pipe due to it’s heating up in the winter time. I tried to look into the temp that the foam is able to withstand which from what I gathered was somewhere around 240 degrees Fahrenheit. My findings also suggest that the mechanical properties of polyurethane foam degrade sharply around 300 Fahrenheit and starts to decompose around 400 Fahrenheit. I’m not entirely sure how hot these exposed steam pipes are able to get but from what I’ve gathered so far it can be over 200 Fahrenheit.
Assuming the excessive heat is not an issue, I am also concerned with the foams expanding properties. I really have no idea the state of the pipe, how worn out it is or not. Essentially I fear spraying the foam back there could potentially put pressure on the pipe, causing it to leak and/or crack.
If anyone has any guidance they could provide it would be greatly appreciated. I’ve also attached a couple of photos of the job at hand.
Thank you all very much for your time!!!
Replies
Welcome to Breaktime.
I honestly can’t answer your question but would imagine shortly you will know how hot it will get. Steam for sure or hot water with radiators?
If you didn’t notice it before, will others notice it?
Is there a draft from that space?
If you can, post a couple pics both from afar and a closeup.
Consider using high-temperature silicone sealant, which can handle heat better than polyurethane foam and won't exert pressure on the pipe. It’s flexible enough to fill the gap without risk of damaging the steam pipe.
Unfortunately I am failing to figure out how to upload an image, I tried attaching the appropriate .jpg file within the allowed file size but it's just not posting with the original post.
I am pretty sure it is a steam pipe and not hot water because it only get hot in the winter time, along with the radiator.
Visually it isn't bothersome in the least bit, but it is a large apartment building in NYC and therefore I am mostly just concerned with keeping pests out.
I also have my doubts about silicone because the gap is very large, probably about 3/4" to 1" inch in width and about 8' feet long.
Any further recommendations would be greatly appreciated.