Deck Bracing

When we designed our house with big decks ten feet above the ground I did not consider all of the things that would be necessary to make it happen. The deck is supported by 6 x 6 inch "legs" and on top of those is a frame made from pressure treated 4 x 12s into which the joists are nailed. All of this structure supports the decking boards. Each leg is placed on top of a 3' x 3' x 18" deep poured concrete footing. The thing I didn't consider is the bracing that would be required.

I decided that if it were done right, the angle braces need not look too ugly, and it gave me a little woodworking project to do while the siding and roofing were being installed by their crews. I had argued with the framing subcontractor that it really should have been his job and that I thought it was included in the bid, but I  knew that if I wanted it to look good I had better take the job on myself. So I put together a little workshop in the garage and set about designing, fabricating, and installing the 24 pieces of bracing. Calculating the length of the braces required that I trot out the Pythagorean theorem, something I had not thought about in a long long time. The bottom of the braces had to be bolted in 1/3 of the way down the post, as measured from the top of the post. I rounded off the corners of the 4 x 4s to match the look of the 6 x 6 posts, notched the top and bottom to fit around the deck beam and the post, and drilled them with a drill press in an attempt to get a straight hole. Creating the first brace took several hours but after I had done a few I got it down to about an hour each. 

Our set of plans that were drawn up by the engineer specified "Bracing as required". I asked the engineer what that meant and he said there were several ways of doing it and our framers would know what to do. After our house framing was complete I asked the framing subcontractor about the bracing and he said it was not included in the framing bid. He claimed that we had talked about it early on but that had not been the case as I was still under the assumption that bracing was a part of the line item that said "Deck framing complete". He said that he never includes deck bracing in his bids because homeowners often require very labor-intensive treatments of the bracing since it is always very visible.

I called the county building department lead engineer and asked him what bracing would be required by the building code and he said that we had three options:

• X-bracing on each side of the deck - that would be a large X-shaped brace made of 2 x 6s bolted into place between the posts of the three sides of the deck. These structures would be big and ugly and I could not really figure out a good way to hide them so I decided against X-bracing.
• Hire an engineer to design some kind of custom bracing that employed a combination of lateral braces under the deck framing and blocking nailed between the framing members. This option sounded expensive and complicated and in the end could prove to also be unsightly.
• 4 x 4 angle braces 1/3 third the length  of the post on two sides of each post. there were 12 posts supporting the deck so that meant 24 pieces of bracing that had to be fabricated and through-bolted in place with 5/8" bolts. That all seemed like overkill and a really big job but maybe the best of the three options. 

Installing them meant drilling through the 6 x 6 posts and the bottom of the post and through the 4 x 12 beam under the deck. I found it hilarious that the building department would not allow the electrician to drill a 1/4" hole in an engineered beam, claiming that it might weaken it too much but here I was required to drill all of these 3/4" holes through engineered beams by the same building department. Since I wanted to bolt them on the inside of the posts, I also had to notch out the ledger that supported the joists in most cases. The whole job took about a week but when it was done I liked the look. The county inspector liked them too and they passed his inspection with no modification.   

This view shows deck supports with bracing installed.

Now on to the task of putting on the deck boards and the railings, sizable jobs on a deck this big (854 square feet).