Bringing Existing Floor Joists

If the existing joist system is very close to being sufficient to support a new attic flooring the addition of bridging between the joists may be all.

Bringing existing floor joists. Additional support for the floor joists is achieved by nailing the ends of the joists into headers. Find a replacement joist that is the same size as your floor joist. Since this is a repair of a faulty or damaged floor joist it is imperative to do this project correctly and there are a few big mistakes to avoid. Driving 16d common nails in old hard wood is difficult.

Floor joist bridging is critical to the structural strength of a floor as shown in figure 1. But it s usually best to run the sister joist over the entire span. Yet it is not uncommon to find bridging not properly installed or missing all together. When the sagging joists are level apply a generous bead of construction adhesive to the existing joist.

Common sense tells you that large floor joists can carry more load and spacing joists closer together also increases the load bearing capacity of a floor. Find a new floor joist with these exact same dimensions. The reason was the corners of the new joist when at a 45 degree angle caught the top of the beam and the bottom of the floor boards. The extra two inches of vertical distance when a floor is framed with 2 x 10 joists rather than 2 x 12s can be quite important for example.

Then attach the sister joist using three 16d common nails driven every 16 in. Even if your joists already have a row of bridging at the center of the span adding a row on each side of the existing bridging will stiffen the floor. Properly sistering floor joists is very important and should not be rushed to save time. As a footstep falls on one joist some of the force is transferred to neighboring joists.

Bringing the floor up to code. Section r502 10 of the international residential code states that header joists can be the same size as the floor joists when the header joist span isn t greater than 4 feet but if the header joist span is more than 4 feet you ll need to double the header joist and ensure that it s capable of. Make sure you also buy the same type of joist. Once the joist was vertical it would fit fine hence the slight floor jacking.

Use a tape measure to measure the length width and height of your existing floor joist. But larger is not always better when builders are constructing a home or adding a room addition. Proper bridging distributes the load on the floor to other joists and over time prevents floors from sagging and squeaking do to floor joists twisting and warping.