John Sayers' Recording Studio Design Forum Archive

Hello everyone,

I'd love to get some input on best practices for sealing these types of penetrations while trying to maintain as much of the isolation as possible. I have a 6" coreslab + topper on top of a large basement space. There are a lot of plumbing penetrations that need sealing. There isn't a firestop code requirement, so I'm able to accommodate any solution. So I'm wondering what others would suggest to specifically address reducing sound transmission through the gaps surrounding these pipes. Especially since I've already got such a massive assembly and how much I should practically be concerned with keeping mass continuity.

My initial inclination is to do the common fill/backer rod and caulk fill from above (with a high density, non-hardening, stable silicone caulk). Keeping the caulk layer fairly thin to allow proper cure. Or should I be looking at other solutions such as filling a larger volume with concrete or other dense fill?

I've attached a few pics here to show the tolerances involved.

Thanks everyone

if you check out Mason Industries - they have a number of products designed for sealing pipes through concrete. might be pricey though. another option is the backer rod, or semi-rigid pipe insulation but i'd do multiple layers of the silicone once each layer is set.

Thanks Glenn. Yeah, I did look into the Mason Industries hardware. They always have such interesting problem solving solutions whenever I look there! Unfortunately, I'm heading towards the lower cost territory (long sad story there). Good thinking on the multiple-pass method though. I'll steal that thought! Especially since I'll be doing the labor on this myself

Would you mind sharing thoughts/experience on a good thickness/layering schedule? Reading specs on Silicone caulk seems to recommend max single curing thicknesses of around 1/2", and my obsessive brain just would want to keep layering past 2 or 3 and never stop

i think 1/2" at a time would work. so if you do 2 or 3 layers on each side of the wall (presuming it's probably 8" thick), then you'll have a nice seal and some damping of the pipe on either side of the all.

in theory: should you use some kind of flexible conduit between rooms or does it matter (in reality)?