floor strength

[joeh]

I recently bought a new house and put a pool table (wieghs 600 lbs) in the bonus room over the garage. The floor dropped a 1/4 inch or more within an hour. The builder says the floor is only rated for 40 lbs per sq. ft. and it is dangerous to leave it there. I ended up taking the pool table apart at great expense to avoid having it go through the floor into the garage. The support for the floor is a truss system that is prefab and uses 2 x 10's I believe for the floor part. My questions are: How much weight should a second floor ROG (12 x 20 ft) hold per sq. ft? Is 40 lbs per sq. ft normal?
How much should I expect to pay if I have to pay to get the floor reinforced to support the table?

Thank you.

[Rich]

Yes - 40/sf is a typical loading condition for a second floor.
The floor reinforcing isn't all that much - maybe upwards of a few thousand dollars - but it's all the other things that go along with it. Revamping of the stairs for the additional floor depth - removing and replacing the subfloor and any existing finish floor material.
That's just off the top of my head by the way. And depending on actual conditions it could be considerably more expensive.

[roger g]

Personally I would look at putting a steel beam ( I have a thing for steel) underneath the floor joists in the garage area. To support the beam you put in 2 steel posts at either end and maybe one in the center. The one in the center I hope is in the middle of a 2 car garage. It depends on how much headroom you lose in the garage..

Roger

[joeh]

Thanks for the quick reply. I was told by the construction foreman that the floor would hold a 600 lb pool table but I guess he was wrong. Thank you for the information.

[Rich]

roger - you could attach 2x material to the beam to allow for flush framing the floor. Then you don't need to worry about head room so much.

[joeh]

The floor can be accessed directly from the garage, just have to remove the sheetrock. Also, the garage is about 10 feet high so even headroom is not a problem. It is a double garage with a single large door so I don't think the steel beam would work. I thought I could get TJIs put up in between the 2 x 10s to provide the additional support required. I was looking at a picture of it that I took while it was under construction and three of the 2 x 10s are not sitting on the frame, they are nailed to the side of a board that is nailed to the frame. The builder used metal brackets to put those three up, one of the three doesn't even have a metal bracket supporting it underneath. One or two of these boards was supporting an end of the table, the end that sank 1/4 of an inch.

[Rich]

Placing 9-1/4" TJI's next to the existing joists is a viable option. The main thing to remember is that it needs bearing - so do everything possible to either use hangers or have it sitting on the wall. Depending on the existing framing you may need to shim the TJI's or the existing framing members.

[roger g]

When you say the beam wouldn't work, what do you mean? The beam will definitely work but the column or post might be the problem. The same piece of steel is called a beam when it is installed horizontaly and a column when it is installed vertical. If the column is the problem then you need a deeper beam for the span.
As far as just sliding in extra joists I hope you have the room to jockey the new joists into place at every location. Unless you have done something similar you probably don't understand the possible difficulties that could arise.

roger

[Rich]

Good point roger. The steel beam would be much easier to install than the sistered TJI's for sure. Unless the floor sheathing was removed above. It's not impossible but not easy by a long shot.