Just picked up a new tub. Instructions call for a floor capable of 50 psf… The tub can hold about 500 lbs of water when full..
Problem is the 1890’s house has full-dimension 2×7’s for floor joists spanning 13 feet at about 32″ centres.. Flooring is nearly 1″ T&G board.
How do I calculate the load rating of this odd-ball? Should I bother?
It’s a drop in, so the walls will take some of the load..
Replies
Offhand I'd say forget it. 32" centers with what are essentially 2x8s on a 13 foot span...? Doesn't sound like it's worth doing the math....
What kind of tub did you have in there before? And what did it do to the floor?
Dinosaur
A day may come when the courage of men fails,when we forsake our friends and break all bonds of fellowship...
But it is not this day.
The new tub is roughly 57 long,36 wide and 22 high. The old one was a standard tub, 60 long, maybe 30 wide and 16 high...The floor seems ok, other than some creaks in the morning there is no noticable bouncing or deflection when walking.
other than some creaks in the morning there is no noticable bouncing or deflection when walking
Man, do I wish I could pass that test . . . Occupational hazard of my occupation not being around (sorry Bubba)
You're going to need to reinforce the floor joists. Something like this is probably what you're going to need.
In the event the tub falls right in the middle of the span on the original joists, you might want to consider even tripling them up; normally just doubling them would be sufficient. You can have an engineer calculate it if you want to be dead sure.
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Dinosaur
A day may come when the courage of men fails,when we forsake our friends and break all bonds of fellowship...
But it is not this day.
a) Wall should not be taking any of the load. The lip of the tub is just that - a lip - to stabalize the tub/ keep it from rocking. It is not intended to take a load.
b) 32" joists schedule?! This means the tub is resting on joists that are basically flanking its footprint. I would recommend that you install some bridging between the joists.
c) Where on the 13' span is the load?
d) Are you using some sort of setting bed? - recommended, even if the tub has feet. Is there an apron in the tub?
e) What type/ material of tub is it?
Frankie
Thanks for the reply,a) Good point - the instructions make it clear that the tub should be supported by both the floor and the lip, but not the lip alone.
b) tub is perpindicular to joists, so it runs over 2 joists
c) the load is within 5 feet of one end
d) yes - no apron on the tub - I need to build an island
e) acrylic - drop in - can hold ~240L water so 528 lbs of water worse case.I was surprised how far apart the joists were, but do the 1 inch floor boards make up for anything? Does anyone know of any tables for old houses?
a) "the load is within 5 feet of one end" - Is this the center of the load or the end of the load. Big dif.b) Is the full length of the joists open to install another joist?c) Still install bridging.d) I recommend a setting bed of structolite (USG). Since you are building within an island, the tub will be installed before the deck is installed. Therefore the deck - not structure - is shimmed or mudded UP to the tub lip. Again, the lip won't be taking the load or stablizing the tub until the deck is installed. Plus, the tub won't be stable until the deck is installed unless there is a setting bed.e) Here are a few sites to do the joist calcs.http://www.awc.org/calculators/span/reversecalc/reversecalc.asphttp://www.cwc.ca/design/tools/calcs/SpanCalc_2002/Hope this helps.Frankie
a) not sure what you mean then.. the tub is 90 degrees to the joists, and the tubs long edge is only 2 feet from the wall the one end of the joist s sit on...rough view from the top:///////////////outside wall
|| /
w|==| |==== joist
a| |tub|
l|==| |===== joist
l| _o_/
||============ joistThere's a drop ceiling underneath, so I have complete access. There is some plumbing there, but overall pretty good. I was going to install blocking, since I notice someone removed some, and know one of the joist is starting to twist a little - I guess he thought it was a decorative piece!Thanks again!
Edited 5/17/2005 11:36 am ET by gb
Nice drawing!I was just trying to better determine if the tub rests on one or two joists and to what proportion.F