Thread: Sheathing issue - View from attic

In the process of buying a home and found this during the home inspection.

Experts please comment on severity/repercussions/cost to repair this type of issue. Note home is in an area where it does snow in the winter months.

Thank you!

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For starters, that was done completely wrong.

As for the cost to correct, that would depend on what type of roof covering you have to remove to make the repair ...

... unless someone makes a "repair" from the underside without removing the roof covering - which could lead to leaking of the roof covering.

Plywood is rated to be installed on 3 supports minimum and across 2 spans minimum; that piece is installed on 2 supports and is across 1 span. As installed, the rating of the plywood is unknown (an engineer could possibly calculate the rating, but for that cost you could correct it).

The proper correction is to remove the roof covering over that piece and for at least 2 feet to either side (or to both sides), remove that bowed piece of plywood which could give way and fall into the attic with the snow load (which may be why it is bowed now - from the weight of the snow), then install a new piece of plywood across at least 3 supports and 2 spans. Then re-install the roof covering.

The repair from inside would be adding blocking along the edges and then a center support, pushing that existing piece of plywood back up, but ...

... that is what could cause the roof covering to leak - pushing that existing piece up and flexing the roof covering. That, to me, would not be an acceptable repair.

By the way, the minimum size of that piece of plywood perpendicular to the face grain is 24 inches.

Thus, the minimum size for a plywood (or OSB) repair is 24 inches perpendicular across the face grain by 48 inches parallel with the face grain.

Jerry. Thank you! Great information. Very helpful!

Jerry, you mean if I were going to repair a 5" hole in my roof, I would have to cut out at least a 4' X 2' section of decking to replace? Is that a nation-wide code?

That repair was obviously done poorly. Looks like the plywood is too thin; should be at least 5/8". No H-clips and probably poorly attached. But if it were done well it seems like the size shouldn't be a problem - however, I don't know codes, I'm just going by experience here.

EDIT: Oh, Jerry is talking about plywood ratings I see, not building codes per se.

EDIT 2: And now that I think about it, we always avoided sheathing spans of fewer than 3 rafters/trusses, and since apparently the whole 4' width of the sheet has been replaced, I can see how it might now be necessary to replace a 4' X 4' section. Unless it would be possible at this point to push it up and block it, but I suppose the inspectors here wouldn't like that idea.

(this is me arguing with myself...good thing I don't normally do it online)

What did your home inspector say? What was on the roof, and is this a patch or some other anomaly? (Pic is of little help...)

Originally Posted by Kristi Silber

Jerry, you mean if I were going to repair a 5" hole in my roof, I would have to cut out at least a 4' X 2' section of decking to replace? Is that a nation-wide code?

EDIT: Oh, Jerry is talking about plywood ratings I see, not building codes per se.

It is in the building code too: (bold and underlining are mine)
- R803.2.2 Allowable spans. The maximum allowable spans for wood structural panel roof sheathing shall not exceed the values set forth in Table R503.2.1.1(1), or APA E30.

- TABLE R503.2.1.1(1)
- - ALLOWABLE SPANS AND LOADS FOR WOOD STRUCTURAL PANELS FOR ROOF AND SUBFLOOR SHEATHING AND COMBINATION SUBFLOOR UNDERLAYMENTa, b, c
- - - (make sure to read notes b and c)
- - - b. Panels continuous over two or more spans with long dimension perpendicular to supports. Spans shall be limited to values shown because of possible effect of concentrated loads.
- - - c. Applies to panels 24 inches or wider.

"continuous over two or more spans" = 3 supports

By the way, APA E30 says the same thing.

Looks like a patch to me.

Couldn't find that about sheathing and spans in whatever version of codes I'm looking at, I think it's an abbreviated version. But I'm not surprised, and it makes sense. I should have thought it through before writing. Just seems such a shame to have to tear off a large patch of roof because of one sagging bit.

- TABLE R503.2.1.1(1)
- - ALLOWABLE SPANS AND LOADS FOR WOOD STRUCTURAL PANELS FOR ROOF AND SUBFLOOR SHEATHING AND COMBINATION SUBFLOOR UNDERLAYMENTa, b, c
- - - (make sure to read notes b and c) c'mon, it doesn't really say that! Does it?
- - - b. Panels continuous over two or more spans with long dimension perpendicular to supports. Spans shall be limited to values shown because of possible effect of concentrated loads.
- - - c. Applies to panels 24 inches or wider.

"continuous over two or more spans" = 3 supports

By the way, APA E30 says the same thing.