Wood Blocking in Stud Walls
Wood Blocking in Stud Walls
(OP)
For wood framed walls I have seen the following general notes:
-Provide wood blocking at 4'-0" max o/c - typ. (seems like overkill to me!)
-Provide wood blocking at mid-height of all load bearing stud walls (works fine for short walls, but I would be less comfortable with that for tall walls say 20 ft and above)
-Provide wood blocking at 8'-0" max o/c - typ. (seems more reasonable, since most walls 8'-0" high that are sheathed and drywalled don't need additional blocking) Is the blocking intended more for temporary conditions, where the wall may get loaded before it gets sheathed on one side? What max. blocking spacings does everyone else typ. use in your general notes?
-Provide wood blocking at 4'-0" max o/c - typ. (seems like overkill to me!)
-Provide wood blocking at mid-height of all load bearing stud walls (works fine for short walls, but I would be less comfortable with that for tall walls say 20 ft and above)
-Provide wood blocking at 8'-0" max o/c - typ. (seems more reasonable, since most walls 8'-0" high that are sheathed and drywalled don't need additional blocking) Is the blocking intended more for temporary conditions, where the wall may get loaded before it gets sheathed on one side? What max. blocking spacings does everyone else typ. use in your general notes?






RE: Wood Blocking in Stud Walls
Thread173-95297
RE: Wood Blocking in Stud Walls
RE: Wood Blocking in Stud Walls
I was thinking a bit more about this and also reading up on the wood design manual and I think the 4' blocking dimension is suited for a wood shearwall application in which the plywood sheets are placed in a horizontal, overlapping pattern. This effectively ties the edges of the plywood to the wall and gives you the full "blocked" shearwall design values. If the blocking is not placed at all plywood edges, then a reduction factor is applied to the shearwall strengths to account for it being an "unblocked shearwall"
RE: Wood Blocking in Stud Walls
While local engineering societies provide that personal relationship tie, Eng-Tips sort of does this as well. After spending some time on the site, you get to "know" some of the handles and get a flavor for their expertise and preferences.
RE: Wood Blocking in Stud Walls
I know this thread is old but can you site the literature which provides a reduction factor for an unblocked plywood shearwall? What is it?
Thank you.
RE: Wood Blocking in Stud Walls
RE: Wood Blocking in Stud Walls
The NDS chapters 3 and 4 provide guidance on unbraced lengths of compression and flexural (bending) members. sometimes blocking is needed to satisfy the l/d and d/b criteria.
RE: Wood Blocking in Stud Walls
DaveAtkins
RE: Wood Blocking in Stud Walls
Building tip: When we use the 10' high walls we use a two foot rip of PT plywood (w SST nails) at the bottom, fully blocked.
RE: Wood Blocking in Stud Walls
Where in the Code does it say that you can use unblocked horizontal diaphragm values for a vertical shear wall?
DaveAtkins
RE: Wood Blocking in Stud Walls
The APA has a document "Report 154, Wood Structural Panel Shear Walls" where they talk about unblocked shear walls and give some ultimate loads. They are sensitive to wall stud spacing. Their use doesn't seem to be supported by the IBC, so I wouldn't design one. Maybe this info. could be of use if you had to come up with the capacity of a shearwall that had been built without blocking, maybe in an older building. Since NY only recently went with a model building code, I wouldn't be surprised to find some older buildings having unblocked wood shear walls. You can download it from the APA website.
RE: Wood Blocking in Stud Walls
APA discussed shear walls in:
Design and construction recommendations for engineered diaphragm systems in floor, shear wall, and roof systems. Updated December 2004. (Form L350 - 32 pages)
I use Florida building code and I could not find a requirement for blocking in my code book. I see unblocked homes all the time in my area. I agree though, anything I design is blocked.
RE: Wood Blocking in Stud Walls
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RE: Wood Blocking in Stud Walls
RE: Wood Blocking in Stud Walls
RE: Wood Blocking in Stud Walls
If you have something like trusses with deep energy heels, I question if metal clips can transfer roof diaphragm shears into the wall. In the case of wind, there might be an uplift force concurrent with the lateral force, and you have to check the clips with an interaction equation. I have seen test results for shear transfer between a sloped roof diaphragm and walls without blocking, and the values increase when clips are used. However, these tests were based on trusses with heels that were about 6" deep. With something deep like an energy heel or I joist I think there is an increased tendency for the truss or I joist to overturn. For these situations, I think you need full depth blocking. The APA Engineered Wood Handbook goes into this, I found it helpful. The transfer of roof diaphragm shears into the walls is an area where it seems like there is not a lot of agreement between engineers. Prior to adopting the IBC, I never saw full depth blocking in my area.