Floor Bounce

Q: When I bought my house, the VA inspected it, and i also paid for a home warranty inspection (not required). Both gave me the thumbs up. I wish I had crawled under the house myself. I would have noticed that the floor joists were 2x8. Well 2x8s on a 10-foot span doesn’t seem kosher to me. Luckily all the plumbing is run below the joists, and I am planning to sister 2x8s to the existing joists with glue and nails, and this will hopefully take the bounce out of my floor. Suggestions or comments.

A: It is not going to be easy to maneuver the new joists into position and on to the sill plates. Remember that the crown must face up and the weight of the current floor is forcing the floor joists to flatten at the crown. Although you said that the plumbing would not be a problem, what about the electrical?

Without seeing the actual positioning of piping this suggestion may not be workable. I would run a double joist perpendicular to the old joists down the middle of the floor, so that the old joists were now supported in the middle as well as the ends. Depending on where you are, you may have to put in a footer, but only at both ends.

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Ceiling Joists Bearing Weight‏

Q. I am planning on installing drywall to my garage ceiling, to give it a more finished look. I am concerned about the load on the joists since there are only 2x4's from one side of the garage to the other 20' total length, supported in the center by another 2x4 attached to the gable. Additionally the joists are spaced every 32". I suppose the 2x4 are there only for lateral support and not meant to support a load. Other houses in my neighborhood have installed drywall after initial construction, and were built is the same way as my garage.

I am planning on installing more 2x4's to make it 16" on center, and install 4 pieces of 4x8 1/4" plywood on top of the rafter for light storage and than install thin drywall 3/8" I think. Also the garage dimensions are 20x20.

That's the scenario, my question is, is there a formula that I can use to find out how much of a load these 2x4 joists can support safely?

Would adding additional 2x4's to the existing 2x4 joist's work? Make it two or three 2x4's wide.

Also I can't seem to find good Douglas Fir 2x4 that are 20' in length, if I added a 16' length and a 8' length for a total of 20' would that still add support even though it isn't one solid board?

A. Adding a second 2 x 4 that does not extend the full length does little if anything to add load ability.

What I would suggest is add a double 2 x 4 sandwiching a piece of 1/2" plywood, joint staggered as the joist in between to make your 16" centers.

Use construction adhesive and nails when making the sandwich. 3.5" nails driven in on an angle, a 5 pattern (dots on a dice), construction adhesive on both sides of the plywood.

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