I’m renovating a house in Colorado that was built in 1970. The exterior of the house has the following type of surface structure moving from the exterior to the interior:
A pressed board 4’x8′ type sheathing/siding (not T-1-11), over a Weyerhaeuser insulating board type sheathing that provides an R value of about 1.32. These 2 layers are attached to standard platform framing. There is no housewrap or vapor barrier either on the inside, or the outside.
I’m planning on installing Certain Teed fiber cement lap siding in place of the 4’x8′ pressboard siding & presently there is no plywood or OSB on the exterior of the house. (I guess the existing siding provided the lateral strength). My question is, should I first install 4’x8′ sheets of OSB to provide the lateral strength before installing the Fiber Cement siding, or will having just the fiber cement siding provide the necessary physical strength requirements?
Edited 6/17/2002 1:21:22 PM ET by MIWUK
Replies
Hi, MIWUK-
In cases where sheet goods such as T-111 are used, they usually are sufficient to provide the wall's shear strength that you mention. However, if you are installing FC lap siding you must use sheathing such as 1/2" OSB for shear. Now, if you are using FC sheet goods, well, I've installed it without sheathing for one of my employers, but now that I think about it I'm beginning to wonder if FC sht. goods can really be counted upon in shear.
So, I guess it depends on what form of FC you are using. Anybody know how FC sht. goods perform in shear?
Ken Hill
Hi Ken,
Yes I am installing the FC lap siding, and not the FC sheet goods, and I am going to be removing all of the old, existing 4'x8' particle/press board siding because it is rotted.
I did call Certain Teed today and I did run the question by them, but I only spoke to a phone jockey and she told me that as long as the insulating board I have is not over an inch thick, that I should not have a problem. I'm not sure if she quite understood me.
As it is, I am leaning towards installing the OSB for the shear strength as you have indicated.
Although it sounds to me as though you`ve already answered your own question....install the OSB.J. D. Reynolds
Home Improvements
"DO IT RIGHT, DO IT ONCE"
Let me complicate the situation a bit:
I've got a 1910 vintage home which had vinyl siding in very poor condition. I ripped it all off to find a real hodgepodge underneath; some rabbetted horizontal lap siding (the original siding, it appears),some asphalt shingle siding over wood covered with 1/2" fiberboard to level it out prior to the vinyl; some half t&g 1x8. Anyway, its all pretty solid everywhere; I was just figuring to wrap it in housewrap and cover it with 8 1/4" f/c hardiplank lap siding.
Given that the house has been standing for so long with its original construction, I figure I can do without another layer of sheathing. Am I mistaken?