Floor joists – Part II: beams and joists

The setup

With the rim joists installed, it was time to install the two double beams. They are 20 foot 2×12’s sandwiched together with 1/2″ bolts and nuts, there are 4 boards in each of them, and they span 40 feet across the house, supported by 5 piers each. There are two of these beams. I decided to install one, then attach all the floor joists to it, then install the second one later. Space is at a premium inside my cabin with all the lumber and osb stacked inside.



When I set the forms for the inner piers in the ground, I didn’t know how beautiful a water level could be for making things flat. I remember there was a lot of rain, some issues with the inspector, scheduling help from the kids, having to bury the pier forms the night before the concrete truck came – it was kind of a rush job due to the weather. All of that meant I could only hope that the piers would be at the correct height on pour day.

Installing the double 2×12 beams

Well, they weren’t level. So, I boxed them in with scrap wood, and made more concrete – I used something like “5,000 psi +” concrete to make it as strong as possible. This brought them up to the correct height, using the water level to figure out where that would be.

My wife realized that it was our anniversary during one of the pours, and gave me a nice little reminder of what we are building – a home:

she’s a keeper. 🙂

With the piers now at the correct height, I worked on installing the double 2×12 beams.  The beams sandwich the rebar coming up out of the pier – this is accomplished by cutting a little channel for the rebar to fit in on each beam, and then tightening the bolts on the beam. At that point the beams grab onto the rebar and hold tight. They should be plenty strong.

1st double beam in, and 1/3 of the joists installed.

With both beams in, I could work on the rest of the 2/3’s of the joists. I think there are around 90 joists in this house. I made a video of some of the details of installing the floor joists here.

all the joists are in!

One small detail- boxing in the RPSL’s and GSL: I got a little creative here, but the subfloor needs something to sit on, even next to the RPSL’s:


Next steps

There are a few places where the beams “crown” a bit- they bow. The recommendation is to place the beam so the bow is on top – like a rainbow. Over time, if the beams settle, the bow goes away. Some of my bows were a bit more than I was comfortable with, so I got a planer and shaved off the most offending areas. I didn’t shave any of the joists – just the beams and the rim joists. I want to completely avoid a squeaky floor.

Once I feel good about how level everything is, I’ll glue and nail the osb panels. This would be easy, but I have to cut around the RPSL’s, and then there’s the issue where the logs make it so none of the house is square – there’s no reference point. That’ll be in the next post. 🙂

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