How to Strengthen Floor Joists From Beneath

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How to Strengthen Floor Joists From Beneath: A great way to reinforce floor joists is to install plywood sheets parallel to them. Centering the plywood will expose the ends of the joists. Other effective ways to reinforce joists include using rigid steel straps, building walls or beams across them, or adding a second layer of plywood. These measures will help keep the floor from sagging or bouncing. Read on to learn how to do this.

Concrete or brick columns

To reinforce floor joists in a crawl space, consider adding concrete or brick columns. Brick or concrete columns will run perpendicular to the joists, and can be attached with adjustable brackets. These columns eliminate the need for shims. Another option is to install beams, also known as girders in California. These beams typically measure four to six feet by eight inches.

While the installation process is simple, you must allow the concrete or brick column to cure. If the settling continues, additional shims may be needed. The distance between the columns is dependent on building codes at the time of construction. For large homes, you can install engineered fill on load-bearing walls. The installation process takes a day or two. Once complete, the joists will no longer settle.

Pressed wood

You can strengthen the floor joists from beneath by installing a second layer of 3/4″ compressed timber. The compressed wood should perch on the principle bar and square divider. It should run the entire length of the joist. This will ensure the floor joist remains sturdy. Once this is done, the next step is to nail or screw down the top layer. If this method doesn’t work, you can replace it with pressed wood.

In case your floor joists have cracks and are sagging, press the wood into the joists. The pressed wood will act as a band-aid. In addition to this, you can add mid-range pillars to the joists if they are bouncy. Alternatively, you can stick segments of compressed wood to the joists to provide added support.


Floor joists are the main structural members of the floor, but they rarely span the entire width of the house. A wall or beam supports them at the center of the structure. This makes it essential to reinforce these beams before reinforcing the joists from underneath. Steel reinforces floor joists from beneath, but not too much. Steel reinforcing plates can be installed on either side of the beam.

A steel flitch plate is another way to reinforce floor joists from underneath. Steel flitch plates can be sandwiched between two floor joists, or bolted to the beam. The steel flitch plate is a strong option for strengthening floor joists, but it limits your ability to drill through the joists. Sistering is a good alternative to steel flitch plates. Sistering is effective when joists are sagging due to improper construction.

Pneumatic nailer

If your home’s floor joists are showing their age, it may be time to upgrade them. A Pneumatic nailer can be a useful tool. A pneumatic nail gun works well for toe nailing, since you can avoid moving the stud. It is important to use a nail gun made for framing to avoid loosening drywall nails.

To do this job, you should first align the stud and joist, and then line them up so that they are flush. Use a 16d nail to nip the blocks in place. You can use two nails per square, but three is even better. To reinforce the blocks, cut the lumber to a little bit longer than the joist. Then, cut the square so the lower edge is flush with the joist. This will prevent any bumps from occurring at the top of the square.

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