How do I make my floors more stable?

Question

My builder did (what seems to me) a cut rate job on my floors.

When I walk around in my house my table and entertainment center (and other such things) shake as I walk past them. (Heaven help me if someone jumps!)

My basement is not finished, so I can get at the underside of my floors. What can I do to make them more sturdy?

What immediately pops to mind is just go an measure and cut a bunch of 2x4s and put them cross ways. Does that sound like a good idea? Are there hidden gotchas? Is there a better way?

Answer 1

It sounds like the joists aren't properly fixed to the walls or they aren't big enough for the task at hand - keeping your floors up.

I'd get another builder in to take a look and quote for remedial work and then try and get the first builder to either sort out the problem or pay for someone else to do the work.

Answer 2

I am not a home builder, but my guess is...

1. They did not glue down the subfloor. Running a bead of liquid nails on the joists just before you lay down a sheet of plywood greatly locks things together.

2. The joists are simply too small, or not properly anchored at the ends.

3. There is no cross bracing between the joists. This will leave them more flexible.

All of these things will help to stabilize a floor. When the various members are solidly locked together, your house will be come quiet and stable.

You might go into the basement and look carefully at what happens when someone walks heavily around upstairs. What is flexing? How is it moving?

Definitely talk to an inspector or engineer to get a good explanation of what was done wrong. Find somebody you can trust. Of course, getting the builder to make it right will be difficult, and anyway do you really trust the cheapskate to do it right even then?

Were it me, I might consider adding a sister beam alongside a few of the existing joists that are flexing. You can even use liquid nails to glue it to the subfloor when you put the sister beam in place. This will stiffen them. Add cross braces, in the shape of an X between the joists. For a few hundred dollars out of pocket, you can do a great deal to reduce the problem.

Answer 3

You could add additional bearers if that's practical (I don't know the construction methods used where you are). Alternatively, cross-brace the joists. i.e. You install bracing from the top of one joist to the bottom of the adjacent joists, and vice versa. While this won't entirely compensate for what appears to be insubstantial joists it will help because each joist will better assist its neighbours to support the load and reduce flexing.

Answer 4

I'm sure you want this repair to be as minimally invasive as possible, but if you're considering replacing carpet or installing new flooring... Laminating the subfloor can do a lot to stiffen it up as well.

Adding bracing underneath may be helpful, but sometimes very difficult in practice. Laminating another sheet to the existing subfloor is usually a relatively simple procedure and generally very effective.

Flooring contractors do this to support heavy tile floors or to eliminate creaking/flexing - they'll ensure the old subfloor is solid and attached firmly to the flooring joists, and then sheet over the top, glue/screw the new sheeting to the old subfloor while ensuring the joints are staggered between the old floor and the new sheet.

In essence you're creating a 1"+ thick sheet for your subfloor which should be pretty solid underfoot.

Good luck!