Remodeling Bathroom, need advise on weight loads

[jwhitley]

I am having a bathroom remodeled and am having an old shower taken out and a tub put in. The Kohler manual says flooring must support 1100 pounds. Floor joists are 2x10 16inch center over a 10ft span. Tub would be in corner of house but run parallel with joists and so would only sit over 2 joists. Will this work?

[David]

I'm sure Don will have some better info.

Here is the calculator I looked at http://awc.org/calculators/span/calc/timbercalcstyle.asp

2x10 joists at 16oc should span 10' with a load of 100psf and deadload of 10psf. What are the actual dimensions of the tub? Do you know the lumber species and grade? Since it's in the corner, those joists probably have a higher dead load.

If the tub is 11sf, or more, you could be okay. The subfloor helps distribute the weight over the the adjacent joists. But 1100lbs is probably too much to rely on the subfloor to distribute well. So if I were you, I'd be absolutely sure that the tub isn't directly over only 1 joist!

[jwhitley]

The outside dimensions of the tub are 60x32 but the interior dimensions are only 42x22. This is going to be a drop in tub and it looks like it sits on 4 support blocks. I am assuming they are 16 inches apart but it does not say on the schematic on the web site. It does say that that it must beable to support 80psf. I dont know what type of lumber it is.

[Don_P]

Welcome jwhitley, I'm just a carpenter, you're getting your money's worth :).

I did it the best I know how without digging deep. I put it on one joist in midspan, it failed, but not by a whole lot. I got comfortable at 800 lbs midspan on one joist using what would be average lumber values. That's total load on the joist, I'm comfortable, its up to you to check further if needed. David makes a good point about checking out the subfloor, now's a good time to replace it if needed. It would make it easy to sister a joist if close or block the ply across the tub front edge. Keeping that ply stiff and well supported will help keep it caulked and dry over time. The main framework is plenty stout enough, see if you need to take care of any point loads. I assumed a tub with an apron. If its something like a clawfoot, blocking the ply under the feet to the adjoing joists would be a good thing.

[jwhitley]

Not sure what is under the shower. The current subfloor has 1x8 pine boards then plywood with linoleon glued to it with carpet on top of that. My intent was to remove down to the 1x8's and replace with 3/4 plywood. i will be putting down tile around the tub. What do you mean blocking the the ply to the adjoining joists. Thanks

[David]

blocking - I believe he means to put a 2x10 between the joists at the front edge of the tub because there is a specific point that is taking on weight. Use a block nailed between the joists to transfer the load onto the joists. Without the block, the ply ends up trying to distribute that weight.

[jwhitley]

I appreciate all the info above. What I dont understand is why Kohler says the floor needs to be able to support 1100lbs or 80psf. This tub weighs 70 lbs and is a 60 gallon tub. If you fill it all the way to the top until it pours out it would only have 500 lbs of water in it. I think that a 200 lb person is not going to have more than 30 gallons max in the tub, again right at 500 lbs. I know that you have to use p for plenty but am I missing something here? Thanks again.

[David]

Call their customer support, see if they can answer it. They're probably just trying to cover their butts.