Laying Plywood Over Floor Joists

Laying your first piece in the outside corner of the floor you want the long dimension of the plywood to lay across six joists with the final edge ending up in the center of the 6th joist.

Laying plywood over floor joists.

Glue down nail or staple down or floating. The plywood sheets lay perpendicular to the floor joists. The method of installation you choose will depend on a whole host of factors but will be one of these. If you can feel some deflection you have two options.

The other option assuming you have access to the open joists from below is to install 2x4 blocking between the joists 24 inches on center. This also applies to joists depth. The chalk lines serve as guides. If raising the floor height is not a problem you can install a layer of 1 2 inch plywood over the existing 3 4 inch plywood.

Fasten your first layer plywood subfloor as you normally should. Once your ply is neatly in place you ll have a great surface on which to install your new floor. You may want to over spec the joists in the home to limit deflection installing 2 12 joists instead of 2x10s. A raised platform of lumber in dimensions of 2 4 or 2 6 with insulation placed between joists and covered up with a 12 inch plywood helps build the right flooring.

The second top layer of plywood joints should not coincide with the joists and the second layer should not be fastened to the joists. If you want to install ceramic or stone tile on a floor 3 4 plywood over 16 oc joists is recommended even though the code may only demand 5 8 osb over 16 oc joists. But the tile contractor must also understand the importance of running the plywood underlayment perpendicular to the joists if he or she is to maximize potential for a successful installation. Chalk lines are pulled all the way across all the joist tops at the 4 foot marks so we can check our accuracy with each sheet of plywood being attached to the joists.

Fill the spaces between the boards with silicone caulking to seal the joints while allowing movement flexibility between sheets. These chalk lines run the entire depth of the momplex perpendicular across each floor joist every four feet. Installing flooring material over the attic doesn t quite leave room for the recommended insulation space needed to provide efficient home energy. Typical floor joists in residential construction sit on 16 inch centers but depending on the framing the joists might be on 24 inch.

The idea here is that for best stability if you can connect joist 1 to joist 6 then movement will be minimized during conditions that cause lateral shifting earth quakes or high winds that can shift the. In fact engineering science for the two underlayment orientations reveals that both the subfloor and underlayment should run perpendicular to the joists without exception.