Step Four of Building a Deck

With your posts set and cut to height you are now ready to put the beams in place. Along with the ledger, the beam supports the deck's joists. A beam is installed on the top of the posts sitting in metal connectors or fastened to the sides of the posts. Attaching the beam to post sides comes in handy when you want to build a deck low to the ground. There are really two options when it comes to beams, you can either buy the beams to the correct size such as treated glulams or treated timber. Or you can make your own beam which can save you a little money. To make your own beam simply take two lengths of 2x material with a 1/2 inch spacer and nail them together. This can save you some money but this application will often twist on you creating sags in your deck. If you do decide to make your own be sure to acclimate your wood by leaving them in the area of the deck for a few days and see what they do. If they twist don't use them, go to plan B. It is amazing what wood can do, a twisting beam can ruin your entire deck.

The first option is to mount your beams on top of the posts. Nail your post to beam connector on top of the posts but be sure not to knock your post loose from the concrete. You can either drill starter holes for you nail or support the post so you don't knock it loose. Cut 45 degree diagonal 2 to 3 inches from the bottom corners of the beam with a circular saw. This process not only adds a nice touch to the deck but it provides a reduction of water absorbing into the grain of the wood. With a helper, set the beam into the connector and make sure you seal the ends of the wood with some type of end sealer. Check that the overhang is the same length at both ends and with the ends of the ledger. Keep the overhang at each end between 12 and 18 inches, and nail the beam into the post to beam connector. Continue this process until all the beams are in place.

The second option is to set the beams on the sides of the posts. Again, you can use this application if you are building a deck that has a height limitation. First align each one of the 2x's with the ledger, then nail or clamp them to opposite sides of the posts flush with the top. Drill two holes through the boards and posts with a 3/8 inch drill. Offset the holes so there is one near each edge of the post. This will provide more holding power and also help from weakening the beam. Secure the beams to the posts with two 3/8 x 8 inch hex head bolts per post.

The next step in installing beams is to brace them. Most people don't do this because it is not necessary but if you want the added support go ahead. Simply use wood bracing or metal bracing if you feel it is necessary. The easiest way is to connect the bracing from the post below the beam to the beam at a 45 degree angle or close to it. My thoughts are, if your posts and beams are going to fail the bracing is not going to help, but if it makes you feel more comfortable brace away.

Now your beams are installed and you are ready for the next step which is installing the joists. If time permits I would highly recommend waiting a few days, even a week or so to see what your posts and beams are going to do. If they are acclimated to your climate everything should be fine, but if not they could twist and create big problems. Next step, installing your joists.