Add Joist To Existing Floor

Sandwiching the member on either side with plywood is sometimes worthwhile but the plywood must be installed correctly for greatest strength.

Add joist to existing floor.

Looks like i will remove the old decking before adding additional joists. Make sure you also buy the same type of joist. For example if 2 inch by 10 inch material is in place the sister joists must be at least 10 inches wide. Measure the width and length of the existing joist.

Bridging or x bracing allows joists to share weight. Thanks to all for your helpful replies and suggestions. Find a replacement joist that is the same size as your floor joist. I do have at least one existing joist that is pretty well rotted.

Then attach the sister joist using three 16d common nails driven every 16 in. Most new construction uses 2 by 8 lumber for joists although 2 by 6. If the attic joists are not adequate one way to strengthen the floor for live loads is to sister the old joists. The best way to limit annoying flex in a floor is to make sure that joists are sized correctly before a house or addition is built.

Hoping there s no more than a couple. In the case of 2x6 joists you can pair them up with additional 2x6 joists by nailing them together side by side. Building codes specify the minimum joist depth and spacing typically 12 or 16 inches on center for spans up to 20 feet but those requirements are intended to prevent plaster ceilings from cracking not to. Purchase the type of lumber that matches the width of the existing joist.

Select or cut sisters that also match as closely as possible the span of the existing. 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. If your floor joist is an i joist for example buy an i joist. But it s usually best to run the sister joist over the entire span.

Find a new floor joist with these exact same dimensions. Use a tape measure to measure the length width and height of your existing floor joist. Cutting the new joists 1 16 longer makes lots of sense as i will be doing lots of the work by myself. Use a sledgehammer or a pry bar to force the bottom of the new joist along the mudsill and center support beam of the floor system or the opposite mudsill on short spans until it s flat against the existing joist.

When the sagging joists are level apply a generous bead of construction adhesive to the existing joist. Depending upon the conditions it is possible to strengthen or repair existing framing members such as floor joists or roof rafters by adding reinforcing material. Sistering is the process of adding a new joist next to each existing joist. Driving 16d common nails in old hard wood is difficult.