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munsonr1 08-06-2011 01:03 AM

Deck Sway Bracing
I have just completed the frame of my deck and am not sure what to use for sway bracing. It is a free-standing deck that butts up to my house. I am going to run the decking parallel to the house, and have read I need to install sway bracing. This can either be a long strip of metal that runs diagonally along the joists, or a strip of 2 x 4's that run along the bottom. I would prefer to use metal, but I am not sure what to look for. says to use a metal T brace. To me, that actually would look like a T. Do you know what I should be looking for, and what I should ask for at the hardware store? I bought some Simpson Strong Tie CS22-R coiled strap, but I assume at 22 gauge, it is not strong enough. Is it better to just use the 2x4 along the bottom?
Here is a link to the explanation. Thanks for any help.

TrapperL 08-06-2011 08:28 AM

The Simpson product they use is called TWB and it comes in several lengths. The issue I see with it is that it's not exactly flat and might leave a slight hump in the deck. It's very easy to install by using a circular saw blade cut and driving it into the cut. To fasten it you will want to use a framing nail gun. Putting nails in it by hand will be a test of patience or you could drill it first. It requires 2 nails at each joist. An accepted practice around here is to use the straps and apply them in an X fashion from corner to corner, both directions.

I highly doubt you'll find the TWB product at a hardware store or a box store. You'll probably end up at a builder trade type lumber yard.

Daniel Holzman 08-06-2011 08:38 AM

I have no idea what code you are operating under. If IRC, you should review the section on sway bracing (called diagonal bracing in the code). See "Prescriptive Residential Wood Deck Constructin Guide", mine is based on the 2006 IRC. Bracing is discussed in detail on pages 14 and 15, see figure 22 for a picture of diagonal bracing (I assume by sway bracing you mean diagonal bracing). Note also the discussion about attaching a free standing deck to the existing house exterior wall on page 15.

Of course, if you are operating outside of code requirements, there are all sorts of ways to accomplish bracing, but use of T strapping is not a listed means in the prescriptive guide. Perhaps you should discuss this with your building inspector first.

munsonr1 08-09-2011 08:56 PM

Thanks for the help. Daniel, I am adding diagonal bracing, but in addition to that I read about sway bracing, which would be more what TrapperL suggested. The only thing I would worry about on that Simpson product you suggested is that I would need to cut through all of my joists. I think I am going to wait and see once the deck is completed if there is any sway, and if so, add the 2x4 diagonally across the length of the deck. I never did see the requirement for sway bracing in any of the code files I saw. Thanks again for the help.

Daniel Holzman 08-10-2011 07:48 AM

I finally figured out what you meant by sway bracing, as you noted it is different than diagonal bracing. I found this definition on

All decks using horizontal decking should have a diagonal sway brace to prevent racking. You may install a metal "T" brace which is a long metal strip diagonally across the top of the joists or install a diagonal deck board across the bottom of the deck frame. Decks using diagonal decking do not require sway bracing.

This description was accompanied by a diagram showing the Simpson style T brace attached diagonally across the top of the joists.

I think this type of bracing is intended to be either a substitute or a complement to diagonal bracing is described in the Prescriptive Guide. By installing a diagonal structural element across the joists, you would effectively resist racking of the structure because of the triangle geometry. I saw that a few builders install the T brace on the bottom of the joists, presumably so as not to interfere with decking installation.

The Prescriptive Code does not discuss this technique, it refers only to diagonal bracing of the posts. Perhaps someone on here has experience with both techniques, and can comment on whether T bracing alone is adequate. On my deck, which is approximately 24 ft x 15 feet, I did not use T bracing, but I did diagonally brace the 6x6 posts. There is no detectable sway in my deck.

Curiously, the term "diagonal sway bracing" is used on the website Inspectapedia to refer to what the Prescriptive Guide describes as diagonal bracing. This confusion of terms is unfortunate, since the Inspectapedia website points out that diagonal sway bracing is designed to stiffen posts and resist racking of the deck, which is correct, however it is a different technique than the T brace described above.

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