Spray foam diy

[mass_burner]

I need to treat a small area ~30 sq ft with foam. Is there a way to do it with cans if SF? Ceiling joist bays.

I don't like rolled insulation. This is an unheated walk through area.

 

[sportbikerider78]

Buy one of the small kits for a few hundred bucks and do another area at the same time.

 

[maple1]

Joist bays, maybe try blocks of foam board cut to a loose fit then seal the edges with spray can stuff.

 

[blades]

Only difficulty with foam boards is possibility of a gap that can allow condensation behind them- that's the beauty of the spray foam no gaps when done right. There several size kits if you dig around some.

 

[velvetfoot]

possibility of a gap

That's why you use the Great Stuff to seal the gap.

 

[johneh]

Tiger Foam kits are the first to come to mind
http://tigerfoam.com/

 

[maple1]

The foam kits might be good stuff - but that would be a pretty expensive 30 sq.ft.

 

[blades]

That's why you use the Great Stuff to seal the gap.

Gap I was referring to could exist behind the foam board- between the board and the sill wall not the area around the edges of the board.

 

[maple1]

This is an unheated walk through area.

Does that mean then that you are insulating on the cold side? Has me a bit puzzled.

 

[mass_burner]

This is an unheated walk through area.

Does that mean then that you are insulating on the cold side? Has me a bit puzzled.

Yes, on the cold side, I'm attempting to insulate the area above it, a corner of the kitchen.

 

[mass_burner]

(8) 2' and (6) 5' lengths. 16" OC joist bays, 9" deep. ~50sq ft.

 

[mass_burner]

Also, the wall above the ceiling transfers cold into the opposite heated space. This is the stair case wall. I guess I can drop cellulose from the top of the wall into the stud bays.

 

[sportbikerider78]

Gap I was referring to could exist behind the foam board- between the board and the sill wall not the area around the edges of the board.

I don't think a gap is a problem as long as you have it pretty well sealed off and warm and cold aren't meeting together to cause condensation. I'd use foam board, sealed into the area with great stuff. Thats still 10x better than fiberglass insulation from a sealing perspective.

 

[blades]

Just mentioning the problem because there have been some incidents of mold/rot caused by this method - likely due to the sill not being properly sealed from the migration of outside air in the first place- same applies to fiberglass batts with out any moisture barrier - likely more so as air/moisture does travel through that medium. So when using Fiberglass is of particular importance to get the edges of the vapor barrier sealed.

 

[mass_burner]

How thick should the foam layer be applied? And should it be applied to the sides of the joists?

 

[moey]

Buy a piece of 4*8 XPS and 2 cans of great stuff. Its about $33 for XPS and great stuff is about $3 a can. Cut it about 1/2 smaller on each side where you need it. Youll need to cut some type of wedges to hold the foamboard in place then seal with great stuff. You dont need to worry about the gap behind if you have small ones behind it. You get condensation when a hot surface meets a cold surface not from a gap.

 

[mass_burner]

Buy a piece of 4*8 XPS and 2 cans of great stuff. Its about $33 for XPS and great stuff is about $3 a can. Cut it about 1/2 smaller on each side where you need it. Youll need to cut some type of wedges to hold the foamboard in place then seal with great stuff. You dont need to worry about the gap behind if you have small ones behind it. You get condensation when a hot surface meets a cold surface not from a gap.

Not sure how practical that would be with all the plumbing/electrical running through this particular area. Plus, there are flooring staples poking through from the hardwood floor above.

 

[blades]

Not sure how practical that would be with all the plumbing/electrical running through this particular area. Plus, there are flooring staples poking through from the hardwood floor above.

plumbing and electric penetrations need to sealed as well

 

[maple1]

Not sure how practical that would be with all the plumbing/electrical running through this particular area. Plus, there are flooring staples poking through from the hardwood floor above.

You'll have to make that call likely - we can't see everything that you're dealing with. Spraying would likely be way easier, just that it would cost more. Is the ceiling already insulated? Could it be sprayed too while you're at it?

 

[Warm_in_NH]

Back to your original post, NO, there really is no way to do a "fan" applied spray foam with the cans you can buy at the store.
By time you spend the few hundred on the DIY kits, (I've seen this go horribly wrong too, either through operator error or leaks and stuck nozzles, etc...) it's probably at the point where it's worth getting an estimate or two from a company that does spray foam.
There's a lot of things you can do yourself, this really isn't one of them, to do it right requires large vats of chemicals, a high power compressor, proper chemical suits and breathing gear.

 

[Seasoned Oak]

The larger spray foam cans with a nozzle kits work really well. The cans are taller and the nozzle allows you to stop mid -job and save a partial can until you can use it later. I think the nozzle kit is less than $20.

 

[moey]

Not sure how practical that would be with all the plumbing/electrical running through this particular area. Plus, there are flooring staples poking through from the hardwood floor above.

Thats your call. I just did a cavity/bay in my garage that had electrical in it. Literally last night. I should have taken a picture I guess. It certainly would have been easier to have someone spray foam it but certainly for one bay a waste of money. To work around the electrical I had to cut the foam board length wise and squeeze it in then spray great stuff in the joint between the two pieces. It also took a while to make wedges to hold it tight while the great stuff dried. Its got drywall on top of it now and Im happy I spent the extra time as fiberglass would not have worked very well in this bay given its size and the way the electrical was.

The flooring staples should not matter I assume they only hang down 1/2 inch or so they actually will help you position the foam rather then having it fall on your head while you reach for something. I did all the rim joists in my basement and they had plenty of nails most I just pressed the foam onto the nail a few I hammered the nail over.

The DIY kits kinda scare me I guess I just dont like the idea of maybe breathing in something that expands once inside me.

 

[mass_burner]

Evidently, there's a good stuff version called wall and ceiling, but HD didn't have it.

 

[Warm_in_NH]

There's a "great stuff wall and floor" but it's a polyurethane adhesive for gluing stuff to joists / studs. Almost bought a can the other day, but I decided to let someone else try it first before I made a mess with it on a job.

 

[mass_burner]

There's a "great stuff wall and floor" but it's a polyurethane adhesive for gluing stuff to joists / studs. Almost bought a can the other day, but I decided to let someone else try it first before I made a mess with it on a job.

So there's no great stuff product for insulating?