Sealing gap between top plate and ceiling / drywall

Old 12-05-22, 01:52 PM
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Sealing gap between top plate and ceiling / drywall

I recently finished installing a drywall ceiling in my garage, overall it came out nicely (especially as I had never hung a single sheet of drywall before). However, there is now a gap of around 1" (a little bigger in some spots) where the drywall is screwed to the roof trusses and the top of the block walls that I would like to seal off to help retain heat in the garage and keep rodents out.

I had looked at possibly using cans of expanding foam, but as I read a little into them, the can needs to be help upside down, which is not possible since the drywall will prevent the can being held in such a manner. Another thread someone had mentioned extending the straw with vinyl tubing, but the poster who was asking about the foam replied that this did not work (the foam I believe expanded in the tubing and pushed it off the can). However, I am wondering if maybe using the vinyl tubing, only a foot or two, maybe less, pushed onto the end of the straw, with the straw still screwed to the can, would allow me to hold the can out away from the ceiling, upside down, and use the tube to guide the foam where it needs to go.

But, is this the simplest option? The walls are just plain cinder block, no plans in the near term to frame them, so need to figure out a solution that will work with the ceiling and block as they are

Old 12-05-22, 06:00 PM
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Posting a pic would be helpful.

When I need a flexible extension on can foam, I toss the straw and attach the proper size tubing directly to the barbed fitting on the can valve; it stays attached better that way. The foam will start setting in the tubing (just as it does in the straw) so set yourself up so you can do the whole job, or at least one foam can's worth without stopping. (you can stop for a minute or three, but not for lunch, say) Consider the cans single use...once you start using them you need to use as much as you can. Once the can sits for a while it seals itself up internally and becomes useless most of the time.

Be prepared for a huge mess...foam will continue to ooze out of the hose for a long time after you release the valve, and it sticks to everything. Wear gloves and old clothes and eye protection for sure. Cover everything in the work area you don't want blobs of foam on.

As an alternative, look at one of the pro or semi pro foam guns with a long nose, such as this one:

This type guns uses foam cans that don't have valves and straws. The can still needs to be upside down, but because of the length of the nozzle, you probably have room to do what you need without a flexible extension. This style gun is so much easier to use than the straw type. The foam stops almost instantly when the trigger is released, and the foam can be left on the gun and reused for weeks or longer without it setting up. And when you remove the can, the gun can be cleaned with foam gun cleaner so it can be used over and over again. (although the partial can of foam probably won't be usable once removed from the gun.
Old 12-05-22, 08:46 PM
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The foam and tubing trick works well. The foam is cured when it comes in contact with water so in winter when the humidity is low the expansion and curing can be delayed or even spotty if you spray it on too thick. Misting with water and letting it soak into the wood and drywall can help.

If you are just trying to close the gap you can do a crown molding. It doesn't have to be anything fancy. A simple 2x2, 2x4 or anything else that strikes your fancy can be used. It closes the gap and finishes off the intersection from wall to ceiling so with some paint it can actually look good.
Old 12-06-22, 12:43 AM
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you can do a crown molding
I was thinking similar, depending on the look your willing to lie with, strips of expanded blue or pink foam could be glued/screwed up into the corner, if would close off the gap and give a bit of insulation.
Old 12-06-22, 12:13 PM
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Thanks for the replies, I had a can of foam and some tubing laying about, so gave that a shot.

Yep... makes a hell of a mess.

I did manage to seal up about about 10' or so before the tube gave me a fit and decided it no longer wanted to be associated with the straw. So, if I continue on the foam route will pick up vinyl tubing that attaches directly to the can a little better, what seemed to happen was that the foam would set fairly quickly in the tubing, depressing the trigger caused more foam to build up in the straw but would then force it's way out where the straw and tubing meet creating more mess.

2x2x8' furring strips are about $3.50 each, vs a single can of great stuff at $6.98 for the big gap filler (plus vinyl tubing at about 49c a foot). Might be a toss up on the cost, the gap I filled with the can I had was bigger than the other gaps, so a single can may end up going closer to 12-15' .... 8 cans. One pro for the cans, they fit in the car better than 8' long furring strips!!

Still, nice to have options, even the foam board cut into strips and nailed / glued is an option I had not thought of.


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