# Sq ft of rimjoists?



## oh'mike (Sep 18, 2009)

14 1/2" Joists--24" on center---? what is the 7? will that be the thickness of the foam?

Foam might be measured in 'cubic feet' --let us know--someone will turn that into cubic feet if you need.


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## charles3526 (Oct 15, 2015)

The 7 is how high the joist is the cavity im mesureing. The 24 is the length of thme joist that hangs over thr house that i want to fill the 14 is how wide each cavity is 

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## lenaitch (Feb 10, 2014)

If I understand correctly, if the joint pocket is 7" High that means your joints are 2x8, unusual but whatever (if so height will likely be 7 1/2"). The cavity is probably actually 14 1/2" Wide for 16" spacing. 24" is a pretty deep cavity but it all depends on your construction. You really only have to insulate the cold-exposed surface. So your area is HxWx# of cavities (7.5x14.5x29) = 3153.75 sq. in. or approx. 22 sq.ft. The volume will include how thick you plan to apply (HxWxDx#)


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## charles3526 (Oct 15, 2015)

Thank you so 400sqft i can buy and have left over 

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## Bud9051 (Nov 11, 2015)

Hi Charles,
I'm not entirely clear on what you are dealing with, but, if that is an overhang and a cavity you are looking at from inside the basement, spraying into a closed cavity can be a surprise. Be careful of any spray that blows back out of the cavity towards you.

I don't see your location, but wait for warm weather and if it is accessable from outside, better.

Sorry if I'm lost.

Bud


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## oh'mike (Sep 18, 2009)

Are you sure that the number you need is 'square feet' and not 'cubic feet'?


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## mako1 (Jan 7, 2014)

I'm assuming what you are talking about are floor joist and not rim joist.
I'm gussing again that you have 2 X 8 X 24' long floor joist spaced at 16" OC. 2 X 8 is a nominal thickness with an actual size of 1 1/2 X 7 1/4. With a spacing of 16 " oc you should have 14 1/2 between the joist.
Not going any further until we get the facts straight.


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## charles3526 (Oct 15, 2015)

This is what im talking about and my mesurements.













































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## oh'mike (Sep 18, 2009)

7.5 x 24x14.5 devided by 1728=1.51
Each pocket uses a bit more than 1 1/2 cubic foot

29 pockets x 1.51=43.80 cubic feet


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## charles3526 (Oct 15, 2015)

Thank you so 200 board ft would be enough for that to be filled in all 29 parts

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## mako1 (Jan 7, 2014)

Man,This was a long way to go to get the correct info on what you were trying to do along with some bad pics.I try and enjoy helping but I like it a lot better when the DIY'er gives some good info and pics.

Hope oh mike has it but it's hard to give decent info when you post something like "I have about 29 joists to cover up the mesurements of them are
24 x 14 1/2 x 7." It would help if some of you would at least do a Google search and get some of the terminology correct before posting.
Sure not the forum police but when I have to sort thru a bunch of posts and replies just to figure out what you are talking about .I lose interest and just don't have the time to deal with it.
Love to help who I can but time is limited for a lot of us and it would not hurt anyone to do a little research first or a Google search.Just saying when your asking for free advice it looks a lot better when you don't mind putting a little effort into it yourself.
Not directed towards the op in particular but a lot of people on these forums.


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## oh'mike (Sep 18, 2009)

mako1 said:


> Man,This was a long way to go to get the correct info on what you were trying to do
> 
> 
> 
> ...


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## charles3526 (Oct 15, 2015)

So 200 board feet is enough to cover my project or do i need 600 board feet to cover 60 cubic ft

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## mako1 (Jan 7, 2014)

You're the man Mike.I've been at this 40 years and tried to make heads or tails of it with the info provided.I finally had a clue after he posted the pics.
Like to help but the op's terminology makes it hard a lot of times.Sometimes it's fun to try and decipher and some times I'm just to damn tired.Glad to see you have a better attitude than I do about it and i'm sure everyone appreciates it.


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## oh'mike (Sep 18, 2009)

Charles--board feet is a measurement used only for lumber--
foam is measured in cubic feet----post a link to the product--


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## charles3526 (Oct 15, 2015)

https://www.sprayfoamkit.com/produc...-rise-anti-microbial-spray-foam-kit-37-detail

This is the one i was looking at its my price range better if i get one a little lower in price if i could 

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## oh'mike (Sep 18, 2009)

That kit only makes 33.5 cubic feet of foam--that's a mighty expensive kit.

Let me see what I can find. What state do you live in?


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## charles3526 (Oct 15, 2015)

Ny

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## oh'mike (Sep 18, 2009)

Thanks.


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## charles3526 (Oct 15, 2015)

Your welcome jusy trying to looking for the most efficient way to do this but also not pay to much. 

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## oh'mike (Sep 18, 2009)

I don't blame you--dang that's some expensive stuff.

I would think that stuffing those pockets with fiberglass insulation and then capping off the opening with some sheet foam insulation might be just as good and a lot cheaper.


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## charles3526 (Oct 15, 2015)

I was thinking that also..i can use batt foam and stuff it. then use foam board or wood to cap it off

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## oh'mike (Sep 18, 2009)

You sure can---simple, inexpensive and available locally.


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## charles3526 (Oct 15, 2015)

Ok maybe ill just do that and being that the batt insulation isnt going to sit flat its going to be bunched up will it still work the same way? 

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## oh'mike (Sep 18, 2009)

Yes it will--r 36 unfaced bats will fill that without bunching it up to much.


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## charles3526 (Oct 15, 2015)

Will do and thank you for all ur help 

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## oh'mike (Sep 18, 2009)

You are welcome!


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## lenaitch (Feb 10, 2014)

Good that you've decided to use batts. I was concerned that trying to fill a 24" deep cavity with foam might cause curing problems unless done in layers (and I'm not sure you spray foam onto cured foam). You have to remember that you are not applying foam but the chemicals that make foam, and I have heard stories about improperly applied spray foam not curing properly and off-gassing to the point that house is unlivable.


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