Gyp. Wall Board Shear Wall

[SperlingPE]

I am trying to use some interior walls (2x6 studs w/ 5/8 GWB each side) for shear walls (keep the load low enough to not have to use plywood).
This looks like a workable scheme until I get to the built in showers. At the showers, we typically spec. cement board and tile. Tile installers we're told prefer cement board. The code (IBC 2006) does not list cement board as a material for shear walls.

Does anyone know of any shear values for cement board?

Does the DensShield or DensGuard product work as a GWB product?

 

[hokie66]

In Australia, we use James Hardie fibre cement board for bracing routinely. As the company also produces and markets its products in North America, it should provide you with the information you require. There may be others in this business as well.

 

[MiketheEngineer]

Do you really need the extra 4' or so that the shower would supply.

Just assume that the these small walls are not helping. Then check your design and see if it works. Install a collector if reqauired - but the double 2x4 header plate usually will work.

 

[SperlingPE]

The shower walls are needed to keep the loads low enough. No opportunity for a collector. I have found information for DensShield 5/8" GWB type 'X'.

 

[MightyPirate]

Have you tried contacting the manufacturer of the cement board? They might have information on using their product as a braced shearwall panel.

Also, you could just spec out water-resistant gypsum wallboard (green board) and the tile installers shouldn't have a problem.

MightyPirate, EIT

 

[SperlingPE]

If by greenboard you mean Densshield, then yes that is what is going to be used.

The old "greenboard" has been found to be susceptible to mold. That is why cement board was used. Now the DensShield product is the preferred gyp board in water environments.

 

[MightyPirate]

Huh, didn't know that about the old greenboard, good to know though (it's what I have in my house).

Anyway, after very quickly reading GP's page on Densshield board it seems that Densshield qualifies under the 2006 IBC as a direct 1:1 substitute for gypsum wallboard.

Just off the top of my head though, I imagine that the exterior shearwalls are OSB/Plywood walls. I remember Breyer's book (page 9.49 6th ed.) talking about how if a shearwall is not as stiff as it's neighbors it may not be taking a load that is equivalent to the usual tributary area method. Keep this in mind that your gypsum wall might be taking less load and your exterior walls might be taking more.

-MightyPirate, EIT