Sheetrock for Sheathing!!???

Hi All,

There are pics from a townhome I just inspected. I put four pics here to give you a good look. There is Sheetrock for sheathing here?? I thought plywood may be on top of the sheetrock, but then it would be un-even? And notice where the hole is cut for piping.

Has Anyone EVER seen sheetrock in place of sheathing? I mean am I COMPLETELY missing something or is this just plain WRONG in any case??? It is not the whole roof just in a part. It is a condo where part of the area that is sheetrock in under a different roof, but only part of it, most of it is just the single roof.

Your thoughts?





It would have to be a product similar to the link I provided.

Marcel :slight_smile: :slight_smile:


I have seen it used[sheetrock] for a fire separation purposes on exterior walls[for brick veneer and stucco] but not as sheathing for roof. I’m thinking they wanted a fire separation between the shingles and structure. Did you notice if it was strapped above sheetrock?

If it’s a townhome, I commonly see the fire barrier between the units extended about 2 attic truss spans up the roof. The sheetrock is under the plywood for fire protection at the walls between the units.

That would be my guess about what is going on here. In one of your pics, it looks like I can see the plywood under the sheetrock.

This is a single story unit. What do you think in this case?..Where the “sheetrock” is, it is an out side wall.

Even with single story units, there has to be a fire barrier between units and I do see the sheetrock extended up onto the roof sheathing. But if it’s on an a wall that is not adjacent to another unit, I do not know what the reason for it is. If there is indeed wood above it, it’s not a concern though, and I don’t see how anyone could get shingles to fasten to sheetrock.

Look at the 3rd photo…there does appear to be wood of some type, plywood or particle board, showing around the flue cutout.

Michael, I saw that, which would create another problem (question), it is particle board. I am having a tough time with this one :frowning:

Hey Greg,

That looks like Exterior Ceiling Board to me. As a drywall contractor, I use that type of board when builders or architects call out for a wallboard application on the ceilings of exterior breezeways, soffits, carports, etc.
The wallboard you show in the pictures has that dark brown (almost black) face paper on it and Exterior Ceiling Board is the only board that I know of that looks like that.
If it is Exterior Ceiling Board, I’ve never seen it used in that application, I’d note it in your report.

I just checked out the USG website and I couldn’t find a gysum based product to be used as a roof sheathing material.
USG sells a SECUROCK Roof Board for use under single-ply and built-up roof applications, different kind of material.

Greg, typically in a wall like this the corners with be sheathed with plywood which provides sufficient shear. the rest of the wall is infilled with various products. Celotex used to be used fo this purpose but drywall can be used.

Drywall does provide some shear strength, and I’ve worked on homes in which the plans called out a particular fastener schedule.

In new Boulder County construction, if the exterior wall covering consists of a combustible material (like wood siding) builders are required to sheath the wall exterior behind the siding with drywall. The downside is that sooner or later, water will get into exterior walls and I see structures go up without drainage planes behind the cladding.

Call out exterior walls sheathed with drywall which have no drainage plane. It’s got to be a vapor retarder… no barriers… no plastic. Water vapor from the home interior needs to be able to diffuse through the wall without being trapped by a barrier on which it will condense.

I agree

Garage separation and between units for 8 feet is what I had read somewhere. The trusses may have been shimmed or designer to accommodate the extra layer but if transitioned across a wide span it may not have been visible from the roof.

Thanks for your answers guys. It is all starting to come together and make sense now. I appreciate you all for taking time to answer this post.

Many municipalities require a “firewall” or total separation between condo, apartment, townhouse, and other multi-family dwelling units.

Firewall separation is usually achieved by masonry brick, block, or gypsum wallboard attached to wall studs, elevated floors, ceilings, and the first 4’ of adjoining rafters. When gypsum wallboard is used it shall be Fire X type (usually 5/8” thickness) rated for this intended purpose. As I recall it is a general 1 hour rating for each layer of Type X 5/8 gyp; hence 2 layers 1 on each side of wall = 2 hour rating. Very specific attention to materials and assembly must be maintained in order to achieve this in the field

There is a vast difference between “separation” and “firewall” assemblies. This mostly has to do with the materials used, the way they must overlap at all vertical and horizontal joints, and are sealed during the assembly and finish applications.

Firewalls are sometimes tested for any points of air leakage this usually does not happen with the common separation barriers we encounter in single or multi-family home construction.

A little tape and a lot of mud slapped around and a builder has accomplished, in his/her mind, the separation intended.


One layer on one side and one layer on other side will not give you 2 hours. It has to be 2 layers on each side to give you 2 hours.

Second that statement.
Sorry Kenton

Marcel:) :slight_smile:

oops, a hazardous typo and i stand corrected, should have left well enough alone or hired a proof reader

meant 2 layers on each side, 4 layers total in one wall assembly = 2 hr.

thanks for the catch and making sure others are aware also!


It happens to all of us!!

public displays of embarrassment are good for keeping one’s ego in check.

Nope, you’re right I was confusing two different wall assembly types.
Boulder CO requires the entire exterior to be covered with drywall under combustible materials. Bad thinking me. No doughnut at bedtime.

Go ahead and have a glazed one Kenton.:slight_smile: