Shed project: Shearwall design

In a free-standing garage, where one wall is almost entirely absent to make a door opening, what parts of the structure prevent the door wall from racking?

I am second-guessing myself about my shed plan. One wall, a gable end wall, is non-load-bearing but is a shear wall. Its plan has an 8x8 door opening in a 12' wide by 9' high wall. I don't have the background to determine whether such a wall will have sufficient shear strength. I'm using conventional 2x4 framing 16" OC with APA-rated 7/16 OSB sheathing, no interior sheathing is planned.

The obvious things would be to reduce the door opening, to use heavier sheathing, and/or sheathe it inside and out. But first I would like to hear any advice this august group has to offer, and with my thanks.

Reply to
usenet-659f31de7f953aeb
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Traditional way, in addition to stiff sheathing, was to cut in angle braces on all the corners. Try to create as many triangular sections at right angles to each other as you can. A large header, corner post to corner post, helps as well. On the addition to my house down south, we actually used about 35 feet of glue-lam all the way from the original house, over the open carport bay, and tied into the far corner of the new garage beyond. It has worked out real well- no movement in 2 hurricanes since then. Carports in Louisiana hate hurricanes almost as much as mobile home in Arkansas hate tornadoes.

I'd bump up the walls to 2x6 (so you can hang shelves on the walls), use thicker sheathing (real plywood beats OSB), consider using adhesive and nails on the sheathing, and use all recommended tie straps for your area. Truss or stick-frame roof? If you aren't finishing the inside at all, you can face-apply the triangular braces mentioned above on the inside, including tying the adjacent walls together at the level of the ceiling joists. That will make for very stiff corners.

Standard disclaimer- I'm not an engineer, but that is how I saw it done as a wee lad, and how I would do it.

-- aem sends...

Reply to
aemeijers

You don't say whether or not you're in earthquake country....

If not, standard let-in diagonal bracing combined with properly applied and nailed sheathing should be fine.

If you are in earthquake or high-wind zone, or just want a beefier design, Simpson makes pre-engineered shear walls designed for the narrow walls next to garage door openings:

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Googling "shear wall design" will get you lots of info.

HTH,

Paul F.

Reply to
Paul Franklin

a door opening, what parts of the structure prevent the door wall from racking?

Reply to
fftt

An 8' door in a 12' wall doesn't leave much to resist shear forces from winds or earthquakes. It would be best to increase the shed to 16' wide, or reduce the door to 6' wide so you can have at least 32" on each side (more would be better).

I'm no engineer, but another option might be to shift the door to one side so you can increase the width of a shear wall section.

Otherwise, the only solution I can think of would be a welded steel "moment frame" that basically makes the entire 12' wall a stiff frame than can't rack. But that could be an expensive option and would probably need engineer approval with the building department.

Regardless, you'll need to tie the shear walls securely to the foundation with special anchor ties (Simpson SSTB) and hold downs (Simpson PHD).

Anthony

Reply to
HerHusband

Bob,

Unless you plan to use the garage as a workshop, in which case 2x6 construction allows you to install more insulation. I used 2x6 framing with R19 insulation in our garage and have never regretted it.

Anthony

Reply to
HerHusband

True...but did OP say where the garage is located? Insulation makes sense for conditioned space.

In most of SoCal insulating a garage is waste of time & money. In the desert (high or low) or the mountains...... insulation is worth it.

cheers Bob

Reply to
fftt

The OP is posting from a SLCC.edu account - Salt Lake City Community College, so it gets hot and it gets cold.

Upon looking at some of the climate data, the shear wall situation is less critical in SLC than in some hypothetical unknown location where conservative advice must be given. SLC has only had two tornadoes in

115 years. Like I said above, let the local code and shear requirements dictate the design - they shouldn't be too onerous. R
Reply to
RicodJour

If you read the responses so far (especially Bob's), then you have a pretty complete answer, but I thought it would be useful to summarize them in one post. The options are:

1) Braced wall panels on either side of the opening 2) A moment resisting frame around the opening 3) A diaphragm above and braced walls on the other three sides

Option 1) can be done with conventional framing and sheathing if the wall segments are wide enough. Otherwise pre-built shear wall segments such as those made by Simpson or Shearmax may be used.

Option 2) can be implemented in wood or steel and requires moment-resisting connections in the corners. In wood this is done with a large header the full length of wall with appropriate detailing between the sheathing on the end segments and the header.

Option 3) works like this: with unequal lateral resistance in the two wall segments running in the given direction, when a lateral force is applied in that direction, the building will rotate, allowing the lateral resistance of the perpendicular wall segments to be engaged to resist the lateral force.

Cheers, Wayne

Reply to
Wayne Whitney

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