post and beam foundation -- where to lay the beams

Hi There,

I would assume that in a post and beam foundation, the beams should sit on top of the posts for better load bearing ability. But in some builds, I see that beams are nailed to the posts. Here is a youtube link   to a builder who I am sure knows his stuff, but he is nailing (see the part between 2:30 and 3:00). Is it because the total weight the beams will carry is not that much so that nailing works? If you were to build one from scratch, would you recommend the beams to sit on the posts rather than being nailed to them. I can see one advantage of nailing the beams, which is that they get tightly attached to the posts. If we were to put the beams on the posts, we can still do it but may require some L-shaped braces or diagonal screws.

Thanks for any insight.

A traditional solution is to have the beams on top of the posts, with diagonal braces - either between the sides of the posts and the undersides of the beams (inside the frames), or from the outsides of the posts to the outsides of the beams. This both ties the beams securely to the posts, and stabilizes the frames - keeps them from moving sideways. "Knees" work the same way, but require curved or bent materials, and if the frames are going to be filled with insulation I assume knees would make it a bit more fiddly.

I don't have any serious building experience myself, but have seen a lot of different wooden structures. Sideways stability is important - knees or diagonal braces of some sort are necessary, unless sheets of stiff material like plywood are attached more or less directly to the posts.

At 3:20 he adds some lags. He only shows them being added to the outside band and they look to be 1/4" or 3/8" diameter lags. In the areas of the US I work in, you would not pass a framing inspection with that method.

You *may* pass a framing inspection if you thru bolted 1/2" diameter galvanized bolt, nut, 2 washers through the outer band and post.

You would certainly pass a framing inspection if you notched the posts to receive the outer band board and thru bolted with 1/2" bolts and had the center beam sitting on top of the center posts or notched as well. This is if the framing members are supported at the appropriate span for the member size and the posts are sized correctly to have a notch.

I am a fan of notching. It is not difficult and can even be done with a chainsaw if you are good with one. If the notch will remain exposed, I use a skill saw and Sawzall to make them look good. If they will be covered up, I use a small battery powered chainsaw. The chainsaw chain makes a rougher edge on the notch and is not as visually appealing as the skill saw method.

Also, if your fasteners ever fail, the beam is supported by the post. If the beam is attached to the outside of the post (no notch) and your fasteners fail, it could cause some serious issues.