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getzjd 05-19-2010 12:05 AM

Best Method for attaching decking lateral support
My deck is about complete and I have a 22' x 23' section of deck that needs some lateral support. I have 3 rows of 4 posts, each spanned approximately 7' apart. 6x6 notched posts and double 2x12 for the beams. 2x12 joists blocked every 8 ft. Height from house starts at about 3' and slopes to about 7' at the furthest point from house.

Not worried about aesthetics as I will have skirting to hide the posts. I had visioned the following method of support

Row 1 - 4ft from house - no lateral support as deck is attached to rim joist

row 2 |\|/|\| - parallel with beam

Row 3 |/|\|/| - parallel with beam

Should I use a 4x4 for support? How should I attach the 4x4 I plan on using for lateral support? Shall I attach the top of the 4x4 to the post or the beam? Shall I through bolt it? If attached to the post, should I attach the lateral \ brace to the inside of the post or the front/back? Would through bolting reduce load bearing capacity of the post? In the future I plan on placing a hot tub directly above the 4 posts closest to the house.


jklingel 05-19-2010 01:10 AM

outta do
Getz: First off, I am not an engineer, nor I have built decks, specifically braced as you intend to do. I looked at you stick drawings, but could not determine what they meant. My first questions would be, on what do the posts sit, how far submerged are they, and what is around them where/if submerged? Crushed rock? Concrete? If you make an X with 2x4s between as many pairs of posts as you can, and bolt them together where they cross, I suspect you will have sufficient diagonals to prevent the posts from tipping, esp if the posts are secured under ground. Bolt the 2x4s to the posts and beams about 6" from the end, or use something that Strong Tie surely makes; "truss bracing", if you will. As for holes in your beams, no sweat. Any lumber company should have pictures of how large of a hole you can have in a beam, and how far from the end, top/bottom, and each other. It will amaze you at how much you can swiss cheese a beam. The reason is because the forces are primarily in the top and bottom, like in a steel I-beam or a BCI (TJI). (Any engineers are welcome to correct me, but that is what I have been taught by an old engineer.) If you are putting a hot tub up there, get a feel for the weight. A gallon of water is about 8 lbs, and any local engineer can tell you what the load bearing capacity of your soil is. I suspect you will need pads at least 16" square under posts holding up a tub. I have a 12' x 42' long deck on my house, with no lateral bracing. 2x10s, 16" OC, 12' long, 3/4" plywood over them. 3 pipes hold up the beam; that is all the support it has, and we do get as much as 2' of snow on it, if it gets ahead of me. Been up for over 30 years; 8' off the ground. Posts are impeded in compacted dirt and sit on/in concrete pads 30" down. I hope that helps somewhat. Good luck. john

getzjd 05-19-2010 06:45 AM

Thank you for the reply. The quick and dirty stick drawings show a row of posts denoted by | with one lateral support between each post / in opposite directions. Then the second row has the lateral support opposite direction of the previous row. For example, if row two has Post | Lateral / Post | Then row three has Post | Lateral \ Post |

As far as the posts, they actually sit on 12" diameter x 33" deep concrete footers set in clay with a 2" gravel base. They are attached to the footers with Simpson aba66z standoff post bases

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