How to calculate capacity of floor joists
Jeff
I am in the process of installing a whirlpool tub on the second floor of my
house. The tub weighs about 700 lbs when full, plus weight of 1 person.
Directly under the tub are two 2 x 12 floor joists spanning 13 feet. I am
wondering how to calculate whether the joists are sufficicient to support
the
weight of the tub.
My second question is is it absolutely necessary to have mortar under the
tub, or can it sit directly on a sheet of 1" ply?
Thanks,
--
Jeff
sciengmba
Jeff <jef...@mit.edu> wrote in message
news:3c868118$0$3935$b45e...@senator-bedfellow.mit.edu...
>
> I am in the process of installing a whirlpool tub on the second floor of
my
> house. The tub weighs about 700 lbs when full, plus weight of 1 person.
...um, only one...?
Harry
"sciengmba" <RMR...@CHARTER.NET> wrote in message
news:u8d19pm...@corp.supernews.com...
So just in case, maybe rephrase the question for 2 people -- or more?
H
db...@sprynet.com
insurance will cover it if you have a problem like the tub falling in...
Or you can go to the library and get a book on wood frame construction.
and see if you can get a book that gives you more than the thickness of
a board, like 2 by 8 inch for a 8 ft. span or something like that.. you
need a book that will tell you how far apart certain boards should be to
give you a PSI, pound per Square inch load carrying ability....
Thomas G. Baker
Jeff wrote:
SYP #2 2 x 12 @ 16" OC will carry 40 psf LL + 27 psf DL over 16'-3". That's
for a uniform load. A concentrated load produces different problems. It will
depend on its relation to the bearing. I think it's time to look at the whole
system that carries the load to the ground. An engineer with experience in
light wood framing could do it quickly for a few hundred dollars. That's cheap
insurance in my view.
TB
sciengmba
considerations, heh heh.
Paul Fritz
A typical whirlpool tub is 5 x 5 = 25 s.f @ 40 lb /sf = 1000 lb
Probably not too much to be concerned about.
Some solid blocking to the other joists would help though.
"Thomas G. Baker" <tgb...@mindspring.com> wrote in message
news:3C8694DC...@mindspring.com...
BP
I have never seen anyone make any special framing provisions and have never
heard of any problems. Your 2x12 floor is way over the required span anyway
(extra strong). If you think about it, that tub fully loaded exerts about
125 psf on the floor system. A substantial human exerts 200 psf if standing
on both feet. That 40 psf figure can be misleading when people take it
literally. The engineering is a little more complex. Perhaps one of the
engineers in the group could elaborate?
If the tub has a base it can be installed directly on the subfloor, provided
the subfloor is level and true, not if there are any voids, imperfections or
need for shimming. In those cases I use expanding foam in stead of mortar,
which tends to crack up and fall out after a few years of service
(especially if that service is "dynamic"!)
"Jeff" <jef...@mit.edu> wrote in message
news:3c868118$0$3935$b45e...@senator-bedfellow.mit.edu...
>
ghost-sniper
> I am in the process of installing a whirlpool tub on the second floor of
my
> house. The tub weighs about 700 lbs when full, plus weight of 1 person.
> Directly under the tub are two 2 x 12 floor joists spanning 13 feet. I am
> wondering how to calculate whether the joists are sufficicient to support
> the weight of the tub.
Sister a 2x12 onto each side of your existing 2x12 floor joists.
You really don't want your tub full of water on the 1st floor, do you ?
MIT, eh ?
BW Smith
full of any number of people and water. The people will of
course displace the water as they are added. The extra
water will either disappear down the overflow drains or leak
tru the floor to the downstairs ceiling. Is a cube foot of
water is any heavier than a cube foot of person? The full
tub weight will remain relatively constant. Weight of wet
ceiling below may vary.
BW Smith
--
~~~~~~ New England Design by CADSmith Studio ~~~~~~~~~
Catalogue of Plans for Homes, Barns, Garages, Workshops:
http://www.cadsmith.com
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
basil...@zotnet.net
wrote:
>If the floor holds a tub full of water it should hold a tub
>full of any number of people and water. The people will of
>course displace the water as they are added. The extra
>water will either disappear down the overflow drains or leak
>tru the floor to the downstairs ceiling. Is a cube foot of
>water is any heavier than a cube foot of person? The full
>tub weight will remain relatively constant. Weight of wet
>ceiling below may vary.
>
>BW Smith
>
The weight of the person plus the water will only be constant if the
person is fully submerged. If a person is standing in the tub or
sitting in it with the upper body exposed, then you have a different
story.
I would figure for weight of tub completely full of water to
overflowing the rim (assume overflow drain plugged) plus 400# of
people in tub as a worst case.
Be sure to include seismic forces if applicable to your area.
Brian Belliveau
"BW Smith" <bws...@cadsmith.com> wrote in message
news:3CE69D53...@cadsmith.com...
> If the floor holds a tub full of water it should hold a tub
> full of any number of people and water. The people will of
> course displace the water as they are added. The extra
> water will either disappear down the overflow drains or leak
> tru the floor to the downstairs ceiling. Is a cube foot of
> water is any heavier than a cube foot of person? The full
> tub weight will remain relatively constant. Weight of wet
> ceiling below may vary.
Eureka !!!
(running through house in birthday suit)
baggy britches
section size is based upon span and joist spacing
the rule of thumb is to double up joists below baths and stud partitions
running parallel