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
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.
On Apr 4, 12:26 am, email@example.com wrote:
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?
On 3 Apr 2007 21:26:06 -0700, firstname.lastname@example.org wrote:
Has actual empty weights and gallon capacities for a bunch
of different cast iron tubs.
Multiply the gallons by 8.3, and add the weight of the
empty tub to get a pessimistic estimate of total imposed load.
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
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
The tub is perpendicular to the joists and spans almost 4 joists.
I just found http://www.cichlid-forum.com/articles/aquarium_weight.php
which 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
Makes sense. Is this true? It so it looks like I would be ok.
has 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
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
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
You should be asking a professionally licensed structural engineer that
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.
On Tuesday, June 28, 2016 at 11:08:37 AM UTC-4, Scott Lurndal wrote:
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.
On Tue, 28 Jun 2016 15:08:33 GMT, email@example.com (Scott Lurndal)
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 homo-whiners-hub for reposting this
On Tuesday, June 28, 2016 at 2:08:32 PM UTC-4, firstname.lastname@example.org wrote:
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.
On Tue, 28 Jun 2016 15:08:33 GMT, email@example.com (Scott Lurndal)
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
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