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-   -   Foam Sheathing (http://www.diychatroom.com/f19/foam-sheathing-185710/)

detroittigerfan 08-21-2013 09:25 PM

Foam Sheathing
 
HI,

I noticed some 1/2" and 3/4" foam sheathing at the store. Does this replace standard OSB sheathing or is it installed over it?

joecaption 08-21-2013 09:43 PM

It could be installed over it, Used to fill the gaps between the strapping when siding a block or concrete wall.
In my option it would be a very poor substute for real plywood or OSB sheathing.
It has 0 shear strength.

detroittigerfan 08-22-2013 12:39 AM

Quote:

Originally Posted by joecaption (Post 1232523)
It could be installed over it, Used to fill the gaps between the strapping when siding a block or concrete wall.
In my option it would be a very poor substute for real plywood or OSB sheathing.
It has 0 shear strength.

Do you mean between strapping as in like furring strips attached to masonry and siding attached to the furring?

detroittigerfan 08-22-2013 07:50 AM

Quote:

Originally Posted by joecaption (Post 1232523)
It could be installed over it, Used to fill the gaps between the strapping when siding a block or concrete wall.
In my option it would be a very poor substute for real plywood or OSB sheathing.
It has 0 shear strength.

Do you mean between strapping as in like furring strips attached to masonry and siding attached to the furring?

joecaption 08-22-2013 08:03 AM

Yes. It adds a small amount of R factor and helps keep the siding from flexing between the strapping.
In some areas 3/4" foam is used for sheathing with Plywood or OSB only in the corners to help keep the wall from racking.
I've lived in one of those homes and any time a real gust of wind came through the whole house would crack and pop.
It was an on going issue with drywall screw pops and seams cracking.

detroittigerfan 08-22-2013 08:09 AM

Quote:

Originally Posted by joecaption (Post 1232649)
Yes. It adds a small amount of R factor and helps keep the siding from flexing between the strapping.
In some areas 3/4" foam is used for sheathing with Plywood or OSB only in the corners to help keep the wall from racking.
I've lived in one of those homes and any time a real gust of wind came through the whole house would crack and pop.
It was an on going issue with drywall screw pops and seams cracking.

Ya I would not trust just foam sheathing. Hey does vinly siding need strapping or draining plane? I was told no because it breathes naturally.

joecaption 08-22-2013 08:34 AM

Guess that depends on where you live.
All we ever do is add house wrap to the wall before adding the siding.
It allows the inside walls to breath and not form a double vapor barrier but keeps the outside condensation from getting to the sheathing.

mae-ling 08-22-2013 09:07 AM

I am guessing the ones you are looking at are not structural, however there are some thicker ones (2") that I have seen that are.
There are also some that are used with diagonal bracing for the sheer strength.

detroittigerfan 08-22-2013 11:23 AM

Quote:

Originally Posted by joecaption (Post 1232662)
Guess that depends on where you live.
All we ever do is add house wrap to the wall before adding the siding.
It allows the inside walls to breath and not form a double vapor barrier but keeps the outside condensation from getting to the sheathing.

In your opinion do you think adding ridid foam to the outside walls helps a lot with reducing heat gain and loss?

GBrackins 08-22-2013 01:40 PM

if you view a home with a thermal imaging camera you'll find that about 15% of the wall surface will transfer heat (studs, headers, etc.). adding rigid insulation board to the exterior side of the wall helps to eliminate heat transfer.

with that said you still have wall bracing requirements in your building code. In some area 1/2" wood structural panel sheathing (4' width) is installed at corners and at least every 25' along a wall. they will use 1/2" rigid insulation board in between the sheathing.

Add seismic and high wind requirements and you'll find a lot more use of wood structural panel.

the area I work in typically requires blocked wood structural panel sheathing on the exterior side of the wall to act as shear walls (due to being in a hurricane wind zone). all exterior walls are covered in sheathing.

I have had projects that required 1" rigid insulation applied to the exterior to comply with the 2009 International Energy Conservation Code requirements for my area. makes for fun with windows and doors.

detroittigerfan 08-22-2013 04:22 PM

Quote:

Originally Posted by GBrackins (Post 1232761)
if you view a home with a thermal imaging camera you'll find that about 15% of the wall surface will transfer heat (studs, headers, etc.). adding rigid insulation board to the exterior side of the wall helps to eliminate heat transfer.

with that said you still have wall bracing requirements in your building code. In some area 1/2" wood structural panel sheathing (4' width) is installed at corners and at least every 25' along a wall. they will use 1/2" rigid insulation board in between the sheathing.

Add seismic and high wind requirements and you'll find a lot more use of wood structural panel.

the area I work in typically requires blocked wood structural panel sheathing on the exterior side of the wall to act as shear walls (due to being in a hurricane wind zone). all exterior walls are covered in sheathing.

I have had projects that required 1" rigid insulation applied to the exterior to comply with the 2009 International Energy Conservation Code requirements for my area. makes for fun with windows and doors.

If your using 1" rigid insulation are you using window with longer jambs/frames?

joecaption 08-22-2013 04:26 PM

Windows and door can be custom ordered with jambs made to size, or for 2 X 4 or 2 X 6 studded walls.
Not a big deal to make your own extension jambs.

detroittigerfan 08-22-2013 04:35 PM

Quote:

Originally Posted by joecaption (Post 1232835)
Windows and door can be custom ordered with jambs made to size, or for 2 X 4 or 2 X 6 studded walls.
Not a big deal to make your own extension jambs.

right but if you add 1 or 2" of rigid foam that increases the wall depth, thus, not all of the window is on the rough sill unless you use replacement windows.

woodworkbykirk 08-22-2013 07:56 PM

build out hte rough opening with 5/4 stock or 2x stock and foam up to that so the window is fully supported..


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