Can the floor hold the weight of a claw foot tub?

Asked by ItalianPrincess1217 (10524) July 9th, 2014

We have been rummaging through this great little warehouse we discovered thats filled with tons of items salvaged from old houses. So many treasures! On our last hunt through the warehouse we found an old claw foot tub that we are looking to purchase. The only concern is whether our bathroom floor can hold the weight of this heavy tub. Do we need to do anything special before installing it? We plan to gut the bathroom anyway but need to know if the type of flooring matters.

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How solid is your floor, what floor is the bathroom on, and what is the floor made of?

I just helped my brother move 4 GD super heavy claw foot tubs (last year) and they sit now side by side on a wooden floor on the 2nd story of the building wherein they now reside.

(Who is carrying the dang tub?)

Dan_Lyons (5426)

Usually, floors are constructed of 2 layers. The wooden floor under the tile/rugs and the subfloor which is usually 1¼” thick.

kritiper (10315)

@Dan_Lyons The bathroom is on the 2nd floor and we plan to put tile down.

You would need an engineer to answer that question. Possibly the city engineer would know.

JLeslie (52555)

Don’t forget that you’ll need to factor in the weight of the water when trying to determine that your floor will support them. Honestly, I’d be surprised if it were a problem. Most of the apartments in this town have old clawfoot tubs, on wood floors of varying quality. I might worry about @Dan_Lyons‘s four tubs, though!

dappled_leaves (15232)

Keep in mind that the entire weight of the tub will be pressing down in four spots instead of evenly spread. Ideally the feet would be above some 2X12s. A gallon of water is ~8.4 pounds. For a big claw-tub you could be looking at around 500 pounds for the water + plus your weight + weight of tub.

You really should at the very least have a licensed contractor take a look. And a engineer too. You will probably be seriously hurt or die if it falls through the floor and if someone is below you when you plummit they will most likely die.

It isn’t terribly expensive to make sure your floor is structurally sound.

And keep in mind that it is a bathroom so you are going to have moisture which will weaken the wood.

johnpowell (12986)

The floor should be designed for the weight to be encountered. This is not an “engineer’s estimate”, but a rough back-of-a-bar-napkin type of calculation:

Let’s say that the tub weighs 500#, which is pretty conservatively heavy unless you have an extraordinarily heavy tub; so you can adjust that weight according to what you know about your intended purchase.

The weight of the tub occupant/s, let’s also estimate at 500# (not you, of course, but let’s say that you and your husband want to use the tub together, or you have an especially heavy guest sometime).

If we estimate the tub’s dimensions as roughly 6’ x 4’ x 3’ (length, width, depth), that’s 72 cubic feet of water, or about 538 gallons of water. Let’s call it 550 gallons. Fresh water weighs about 7# per gallon, so that’s about 3,850#, which we can round up to 4000#, or two tons.

So, adding it all up: a 500# tub, 500# of occupants (and let’s say that they’re standing up, because if they were lying down, they’d displace their weight in water, which would therefore no longer be in the tub), and 4000# of water: 5000# all in. Divided by four support points, that’s 1250# per foot – and yes, that’s a lot of weight if you’re lifting it!

Residential building codes in the USA typically call for structures to be designed with floors that can support “live loads” (which this application is) of 40 pounds per square foot. That doesn’t seem to jibe with the tub weight on four points at 1250# per point. However, the “whole floor” under the tub is (assuming the dimensions of 6’ x 4’, length x width) 24 square feet, and the floor just under the tub alone should safely support 24×40# = 960#. (Again, this is especially conservative, because if you look at other “point loads” in your house, such as a loaded refrigerator, for example, you can locally easily – and safely – exceed the nominal 40psf loading.)

The high-side estimate that I gave you above represents about 5x that weight, so it’s going to be outside of “normal” for a standard just-according-to-the-code floor. However, it would not take extreme measures to stiffen that floor, especially if you’re tearing it up anyway, so that it would be perfectly adequate to support that tub.

Particular attention should be paid to the four support points, as others have already noted, so that local deformation doesn’t ruin the floor surface.

CWOTUS (23898)

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