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jh1999 09-09-2011 10:05 AM

Insulation 'Great Stuff' by DOW Chem.
1 Attachment(s)
See pic please. I circled in RED the effect I would like but can't seem to get the "spray effect" Any help please??????? When I spray I get clumps that roll off to the bottom of joist.

DrHicks 09-09-2011 10:10 AM

The product you're using will not give you the results you desire. Great Stuff is not a spray-on insulation. It's an expanding crack and hole filler.

I wish I could point you toward a product that will do what you want, but I'm not aware of one. Hopefully somebody else can chime in and help. :)

Mike in Arkansas 09-09-2011 10:12 AM

There are several sources of DIY spray foam kits online. Do a google search. Obviously going to contain more than a can of Great Stuff though.

md2lgyk 09-09-2011 11:10 AM

Such kits aren't cheap, either.

DangerMouse 09-09-2011 11:35 AM

GSF should work in this case though, just start at the bottom and work lines up as you go.

......unless this is not a photo of your area.


DexterII 09-09-2011 12:13 PM

Or use rigid foam board, with caulk or GSF to seal the edges.

gma2rjc 09-09-2011 12:14 PM

What kind of spray are you using?

Do a google search for Foam-It-Green. That's what I used and it worked very well and it's easy to do. It was my first try at that kind of project.

If I remember right, there are two different kinds of foam to choose from. One of them is for spraying wide areas like walls or rim joists and one doesn't spray as wide an area. There are also two kinds of tips to use and I think both kinds come with the tanks. Order extra tips because once you stop spraying for more than 30 seconds, the tip has to be replaced - they just snap off and on, it's easy.

I know there is another company that sells to the general public and I think it's called Tiger Foam or something similar. You could look it up and compare prices. I think I paid $700+ for the kit and $95 for shipping. But there are smaller kits for smaller jobs that cost less.

jh1999 09-10-2011 07:05 AM


Originally Posted by DexterII (Post 724559)
Or use rigid foam board, with caulk or GSF to seal the edges.

This is probably the path I'll take. Thanks!!

DangerMouse 09-10-2011 07:11 AM


Originally Posted by DexterII (Post 724559)
Or use rigid foam board, with caulk or GSF to seal the edges.

This is exactly what I did for my perimeter beams with the foam baffle vents.
(scrap foam from the walls cut out for the baffles, GSF to seal/glue/fill gaps.)
It worked fine! Dunno why I didn't mention it before.... :laughing: There are pictures even here somewhere.....


framingrailman 09-10-2011 07:57 AM


Originally Posted by DexterII (Post 724559)
Or use rigid foam board, with caulk or GSF to seal the edges.

Yes, in my home I insulated the area with 6" insulation, then cut foam board to fit, then caulked.

Gary in WA 09-10-2011 05:53 PM

The rim joist is a large source of air infiltration because it swells and shrinks with the seasons;

SPF or rigid foam board directly on the rim wood, air seal then add fiberglass (if required by local code), though IRC now allows foam (up to 3-1/4”) left uncovered in rim area;

The fiberglass insulation should never be between the foam board and exterior;

1. It allows moist air in to saturate, condense and mold on the rim joist (and fiberglass),

You will also lose 60-70% of R-value with wet insulation; add another 20-30 % lost to convective loops and wind-washing the fiberglass. Sorry, framingrailman, don’t shoot the messenger……

2. Any holes from plumbing/wiring need to be plugged with foam (not air-permeable f.g.) to stop the “stack effect” of energy loss due to pressure/temperature differences at attic/basement, or crawlspace.

Foil faced foam board on walls may be approved, left exposed----check with the local AHJ. You’ll want to change it out if/when future finishing.(No foil-faced below grade in basement- vapor barrier).
Remember to fire-block the frame wall every 10' horizontally and seal the top plate to concrete continuous with approved fire-blocking material. AHJ may accept compressed f.g. batt there. Imperative to stop an outlet fire in wall from spreading to joist bay, surfacing at outlet across basement in wall at other end of house, on floor above or attic.


framingrailman 09-10-2011 05:56 PM

I'm going to do an inspection...Thanks, GBR

carlosc 11-23-2011 07:33 AM

As one poster mentioned, what is happening is that you are probably using something like Great Stuff. Your picture is showing a professional installation of foam insulation. So basically, you want to avoid the products 'in a can.' You want to use a foam kit, and they often come in a tank that looks like the tank on your gas grill. They have a 'gun' which allows you to change the flow rate. Take a look at Handi-Foam products. Here is a link to help you out with:

They have a guide to help you as well:

On the guide, that first picture shows a guy using a gun to spray between rafters. Like what you want to do.

Good luck jh1999


cbaur88 11-30-2011 07:12 AM


Originally Posted by DexterII (Post 724559)
Or use rigid foam board, with caulk or GSF to seal the edges.

This is another option I've been kicking around to insulate the ceiling of my crawl space. However I am not sure what to do for a vapor barrier. Forgive me for all the questions I am an anal try to do it right DIYer.

Does rigid foam need a vapor barrier? If so do they make it with a vapor barrier? Also would it be a bad idea to do a hybrid of rigid foam sealed w/ GSF and fiber batts? Should the batts go in first or the rigid foam w/ GSF then the fiber? I would think the rigid foam first then the fiber but want to be sure. Thanks in advance :)

Windows on Wash 11-30-2011 07:45 AM

The vapor barrier in your crawl space should be across the floor and sealed to the step wall.

If you were insulating the floor and not the outside wall, the rigid foam would go across the joists with the cavities being properly filled with FG, Cellulose, or mineral wood.

Flash and batt works pretty well in this case.

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