I purchased a Kohler Villager cast iron tub from my local Home Depot to install in our 2nd floor master bathroom. I removed an old shower pan and am replacing it with this tub. The subfloor is half-inch wood and it is sitting on top of 2x10" joists 16" OC which are spanning
13'.
I asked the gentleman at Home Depot if there was anything I should be concerned about before installing the tub and he said just make sure I follow the directions included with the tub. Unfortunately the tub doesn't mention anything specific about the floor load requirements. It just says make sure your floor can support the tub.
My question is, do I really need to worry about floor load with this tub? I have searched online and couldn't find anything definitive.
We did a test fit with the tub and decided to leave it there as it was extremely hard to get into the alcove. I would hate to have to try to get it back out.
try for two NO answers to these 2 questions: does your home's second floor sway in high winds with its full furniture and occupancy load? if you fill a king size waterbed mattress placed on the second floor, does that change the answer?
Right, I was able to figure out the weight of the tub (plus water/ occupants) but I don't know how to figure out if my floor can support the load. Is there a standard way of calculating the max dead/live load of a floor? I would think these tubs are installed all the time (as it came from Home Depot) and I was surprised there isn't any information in the installation manual about it.
Well, that's what structural engineers do. :-)
If your house is of recent vintage, the floor system should have been designed for at least a live load of 30 pounds per square foot. So figure out the total weight of the tub, water and bather(s) (be pessimistic), divide by the tub's area, and see what load you get. Also if the tub is oriented parallel to the joists, consider how many joists are carrying the tub, and if it is less than [tub width / 16" o.c.], correct for that.
If you come up with a figure less than 30 pounds per square foot, then you are definitely OK. If the figure exceeds 30 pounds per square foot, then you have to investigate further. E.g. what is the floor system adequate for? Some residential areas are designed for 40 pounds per square foot. Or your floor system may be stronger than the minimum, since lumber comes in discreet sizes. Also, where is the tub located in the span of the joists? In the middle would produce the worst effect; near an end of the 13' span would produce much less effect.
Yikes, the tub is 12.6sf and the total live load (tub, water, person) is 800 pounds. That makes the live load about 65psf and the dead load about 26psf.
The tub is perpendicular to the joists and spans almost 4 joists.
I just found
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talks about 1000 pound aquariums. According to that site the
40psf limit is the "minimum" live load requirement and that requirement is for the entire floor... From the site:
"Myth #1: "According to the building code my house can only support a maximum total load of 40 psf anywhere on the floor." No, the 40 psf is a theoretical uniform design live load over your entire floor. You might have a whole lot more than 40 psf directly under your aquarium but that's okay because you didn't fill your entire room with aquariums either."
Makes sense. Is this true? It so it looks like I would be ok.
a good discussion of using joist span tables, but they're really set up for sizing joists in normal rooms with unknown distributed loads. For a fairly large point load like this, you really ought to find a beam-span table, or something that gives joist loads in pounds per linear foot, and figure out the minimum size for the combined load of the full tub, PLUS the 30 PSF live laod and
10 PSF dead load of the rest of the floor supported by those same joists.
You don't really want to just average the weight of the tub across the span, because that will give you unreasonably pessimistic numbers if the tub is near a load bearing wall, and unreasonably optomistic ones if the tub is in the center-of span.
Apparently your tub is perpendicular to the joists, and probably 32" wide and about 56 inches long?
Now if someone knew how far it was from the centerline of the tub to the bearing wall, they's have enough info to actually do a calculation.
HUGE CAVEAT: I'm not an engineer, I just play one on TV. Don't believe what I have to say, go find a structural engineer who will spend 10 minutes performing the proper calculations.
OK, from your description it sounds like the tub is 30" x 60". You've stated elsewhere that the joists are 2x10 @ 16" o.c. and span 13', and that the tub is located with its centerline 6' from one support.
The issue is whether the 4 joists that the tub is sitting on will be overloaded. Assume the floor dead load is 10 psf, the design live load is 40 psf, and the live load where the tub is located is 65 psf. Instead of having to carry just the design total load of 50 psf * 4/3' = 68 plf, the 4 joists have to carry an additional 25 psf * 4/3' = 32 plf over the 30" where the tub is located. For simplicity, assume the tub is actually dead center, 6.5' from either support (a slight pessimization).
A calculation shows that the maximum moment developed by the uniform
68 plf over 13' is 1410 foot-pounds, and that the moment developed by the extra central 32 plf is 247 foot-pounds, for a total maximum moment of 1660 foot-pounds. Now a uniform load of 68 plf (50 psf @
16" o.c.) over a span of 14' also develops 1660 foot-pounds. Thus, _assuming_ the joist design is governed by maximum moment and not by deflection, the question may be rephrased as whether the 2x10s @ 16" o.c. are adequate to span 14'.
So determine the species and grade of your joists (assume #3 unless you know otherwise), and find a span table for your species for a live load of 40 psf, dead load of 10 psf, for 2x10s @ 16" o.c. If the allowable span is 14' or more, the joists are adequate subject to the above assumptions. You may find that a #2 joist would be adequate while a #3 would not be, so then you need to investigate further the grade of your joists.
replying to binister, KC wrote: _We have a similar problem. Kohler stated that the minimum floor load is 52 lbs per square foot for their 340 pound tub. This tells us nothing . Do we need additional support?_
You should be asking a professionally licensed structural engineer that question.
The ICC Residential code requires floors in non-sleeping-rooms to support a uniformly distributed live load of at least 40#/sf (30#/sf in sleeping rooms).
Given that 40 < 52, it would seem that the 340 lb tub (plus water displaced by a 200# human being) would require structural reinforcment.
You gotta love these people that ask questions like that. Like we're going to know if it's new construction on a slab or a 200 year old house that's half falling down already. Never mind the specifics of what's actually bearing the load, we know zippo.
If the solution to everything on alt.home.repair is to call a professional, why not just remove this newsgroup. Even an idiot can open their yellow pages and call a pro.
Do yourself a favor. The next time you take a shit, make sure to call a professional to come and wipe your ass.
By the way, this thread was originally posted on Apr 4, 2007. By now, the OP has probably fallen thru their bathroom floor and drown when the tub flipped over on them, after the cracked floor joists knocked them unconscious. Be sure to thank h*mo-whiners-hub for reposting this obsolete crap.
I notice you didn't answer the question either. How can anyone answer a question when there is zero information? And given that the person asking is so clueless and this is safety related, it seems to me the only safe answer is going to be the one given by someone that knows what they are doing and that can see the construction.
What difference does that make? The person that just revived it has the question NOW. I hardly see the point in starting it all over again, in a new thread, when there is probably some useful discussion already there.
Well we're even then because you haven't told us much.
How much was the sum of the weight of the tub that was there before, plus the water displaced by a 200lb person, plus the weight of the water not displaced by that person. Or the weight of a full tub of water.
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