Exterior wall sheathing?

[krugan]

I have a new home being built and the builder has used both plywood and GP Densglass Silver in other areas. Why a combination of both? Is one better then the other?

 

[SperlingPE]

It depends on where the materials are being used. The wood sheathing product should be used on all exterior walls. Wood sheathing has more capacity to resist lateral loads than the densglas product. Interior walls that go to the roof structure are typically just sheathed with a gypsum wall board (or densglas) product. They could be sheathed with wood because if attached to the roof structure, they will see load.
Residential (in my neighborhood) is typically "cook book" type construction until you get into a custom designed home or a large home (greater than 5000 sq. ft.). So your contractor is probably following what is allowed by the residential code.

 

[woodengineer]

Visit the following thread:

thread726-154036

Jordan

 

[ornerynorsk]

Personally, I would never use anything but plywood for exterior sheathing. Long term, I think a person is just inviting problems by using the gypsum products, osb, fiberboard, or any of the other stuff besides plywood. Theory and real life are often 2 different realms.

 

[woodengineer]

ornerynorsk,

I agree with you with one exception. OSB (which is not to be confused with wafer-board) has great strength values. In fact, it has a higher specific gravity than most plywood therefore giving it a better nailing capacity.

Jordan

 

[scottiesei]

That is old school construction. Alot of builders are looking to save $ now that the market is slowing up a bit. They design the wall to have braced corners and intermediate shearwalls with the plywood/osb. Then the densglas goes in between. I do not like it but it works if properly designed.

 

[krugan]

Thanks for the replies. I emailed my builder and asked why they used a patch work of Densglass and plywood instead of just plywood and their reply was "it's a better product then plywood, it provides more moisture and mold resistance."

I've read that it is good for moisture resistance, but like most of you stated regarding lateral loads, does it invite more shifting in the house, i.e. drywall cracking etc?

I've posted some pictures of my home and some other houses being built where they are using all Densglass.

http://home.cogeco.ca/~krugan

 

[SperlingPE]

Check with local building department to see if this is allowed for use as sheathing. If allowed ask what the required nailing/screw pattern is and what allowable load this will resist. Teh allowable laods for GWB in the code books is less than that of APA rated sheathing.

 

[scottiesei]

Hmmm....Typically building codes require braced wall panels at the corners. It seems on the left side of your home they would need let in bracing since it is not sheathed. That could be something to look into. Where is the home located? What is the local code?

 

[krugan]

Thanks again for your input guys. I just want to make sure they are doing this properly if they're looking to save money using a different material.

The home is being built in Brantford, Ontario. I will follow-up with the local Municipality to try and find out if they are following local codes.

Do inspectors not come and check this type of stuff to make sure builders are following codes?

 

[scottiesei]

They do in Florida!

 

[krugan]

Here is the response I received from the local building inspector:

"In response to your enquiry we wish to advise the following:

Your query is two-fold; Densglass is an approved sheathing product having been evaluated by CCMC. However, the sheathing is not required in this application at Empire Communities.

Allow me to explain;
1. The sheathing required for wind or lateral bracing is achieved by the installation of gypsum board (drywall) on the interior of walls,
2. The cladding products used by Empire (brick veneer or vinyl siding) are attached directly to framing members without need for backing,
3. Empire's use of sheathing is considered an extra by their construction standard,
4. Further, the OBC does not give nailing patterns or loading criteria for sheathing. Where sheathing is required the OBC stipulates the minimum thickness of sheathing required and provides that sheathing is attached directly to framing.

We can advise that homes constructed by Empire Communities are built to the requirements of the OBC. Your concern for the "lack of bracing" will be addressed when interior finishing takes place."

 

[SperlingPE]

GWB can be used as sheathing. The UBC and IBC give it a rating and required nails/screws. The load path to the GWB still needs to be maintained. You run the risk of cracks in the drywall if overloaded laterally. The OBC sounds like it needs updating.

 

[scottiesei]

It is what it is. I guess things are done differently up there eh? I agree with Sperling, they need to update.

 

[davesaudio]

If I read you guys correctly you are critical of the OBC for not recognizing 'glass as a sheer control material.
Does your code accept drywall as such?

 

[davesaudio]

And yes in OBC land one would expect inspections
at the footing,framing,insulation, plumbing and final by local municip, electrical inspectors are provincial