Well, I started using expanding foam as subfloor adhesive, and so far I like it. A little goes a long way, and 4 tall cans did the whole thing. If you decide to do it, have a can of acetone and some paper towels handy, as you end up getting slimed alot.
One nice thing about the stuff is that its so slimy that it makes it easy to slide the sheet around to position it, making for a lot less beating to get it to fit the tongue in the groove. A downside it that it gets tacky in about 10 minutes, and sticks tenatiously. Globules are dry to the touch in about 15 minutes. If you get excess on the floor or groove, wait until it sets up about 15 minutes, as by then it will scrape off easy with a piece of scrap. If you wait too long, its harder to scrape off.
I’m doing the floor by myself, but it would be nice to have two people working so someone can nail off the floor right away, as you’d get better contact. I had to pry a small piece up off half a joist, and it stuck like crazy.
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I told you it could be messy, didn't I?
working alone, another potential pitfall is if you step in it while it is greasy. The bottom can come up at you pretty fast when your feet aren't under you anymore and bouncing off joists is less fun than you might think.
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Isn't glue for subfloors a LOT less costly? A 3/8 bead from a quart tube goes a long way, a can of foam?...I can't see the sense. Cents.
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
A can of subfloor glue foam is equivalent to several 1 quart tubes of subfloor glue. Foam is much more economical, except for the initial outlay for the gun.
Regards,
Tim Ruttan
Edited 9/25/2004 9:38 am ET by TRIMBUTCHER
ok, I was thinking 'greatstuff'...that's how much subfloor I do..LOL thanks.
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
Hmm, so you're telling me I'm going to have a bitch of a time getting them back up if get the impulse to foam them down? Most of what I mess with is renovation crap, and typically I have to do it with at least a thought of how it the renovation might be reversed. Which is why I lean towards the time consuming countersunk screws. Easy to pop them out and pull the sheet back up.
But I don't know if I was answered in a previous thread. Does anyone think fanfold would work under subfloor to reduce vibrations?
The problem with foam is in that application is that you have the loads in a fairly narrows area, the top of the joist and it will crush it.
Also the nailing/screwing of the sub floor to the joist will still tie them together.
Go a google on STC floor assemblies.
STC is sound transmission coeffficent or something like that. I know that for wall assembleies there are a number of web sites showing the affects of different construction. I am assuming the same for floors.
Fanfold might actually make more noise. Subfloor sound usually comes from movement. The subfloor moves from the joist and the sliding nail is what makes the noise. Fanfold or another flexible member in between the joist and the sheet of subfloor would likely make for a lot more squeaky fasteners over time.
By the way, everyone is talking about "expanding foam", and Bill mentions about it "getting crushed". Are you guys talking about Great Stuff, or are you talking about an approved subfloor foam adhesive, like this? I would never assume that the chemistry of one is equivalent to the other...
Regards,
Tim Ruttan
" Bill mentions about it "getting crushed"."
That was a side issue about using fan-fold foam sheets for floor isolation.
But, yes, the sub-floor foam adhesive will get "crushed", but it is still liquid at this point.
great stuff is not structural and will crush from the load. I am talking about the kinds formulated specifically for adhesives.
The expanding foams are a combination of three components
A - the propellant to push it out of the can. This is dispelled into the atmosphere and is not part of the final product.
B - An expansion agent which reacts with moisture and/or oxygen in the air to make the stuff foam up. When it is formulated for insulation/filler/ it has a lot of expansion agent to make it foam up to 1000% the volumn or so.
You can see cans labeled 'low-expansion" which is supposed to only expand up to 300% insteead of ten. This is for around windows and doors so the jambs don't get tweaked too much.
but in stuff formulated for structural glue - the expansion agent is only for about 100% so the structure of the voids is less air and more solids when it cures.
C - Finally, the actual polyurethene solids which are very strong, wear resistant, and have great adhesion - the same reason they are used for floor surfacing.
C
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That link doesn't work anymore... We're doing work soon and I'd love to know what that product is! Especially if that would work for existing subfloors and joists. We're opening up the ceiling and hoping to work from below. Thanks!
Search for Advantech subfloor adhesive. Working from below could get pretty messy with any adhesive. The advantech stuff comes out as a bead of foam and quickly collapses to a gel. The way it's intended to be used is that it is applied to each joist just before the ply/OSB is dropped on it. Not sure if it wouldn't drip down if you tried to apply it to the subfloor instead of the joist.