Possibly unsafe weight on upstairs bedroom floor?

December 28, 2011 12:29 AM

Is it safe to fill up a 150-gallon tub in my bedroom?

I live in a small, free-standing house of unknown age (but built before 1968). I want to know whether filling up a 150-gallon tub of water, which (given expected fill and occupant) would weigh around 1,400 lbs (635 kg), would be dangerous in terms of too much weight on the floor. The tub is about 5 feet in diameter. The tub would be located in my bedroom, which is on the 2nd floor of the house. You probably can't answer this directly, knowing nothing about my house, but how can I find this out without actually trying it? Even if it's "probably safe", are there "best practices" for doing this sort of thing?

The tub would be filled for a few days at most; it's not going to be a long-term thing by any means.

posted by Maximian to home & garden (20 answers total)

I don't really think it would pose much of a problem. It wouldn't be that big of a deal to have 8-10 friends who all weigh 200lbs to stand around in a circle, jump around, dance, etc.

It would be nice if you could center it above a load bearing wall downstairs, but that's probably unlikely.
posted by neversummer at 12:40 AM on December 28, 2011

You need to look at the floor and find out the spacing and size of floor joists. Most residential construction codes call for a dead load of 10lbs/sq.ft. At 5 feet diameter we are looking at approximately 20 sq. ft. which gives us 200lbs of dead load and 800lbs of dead load.

This is just napkin work though and it also depends on how close to supporting walls the tub is, the type of wood and the construction. Sometimes they over-build floors for expected water beds.

Usually the wood will bend pretty significantly before it breaks and if you have sheetrock on the underside of the joists it will (probably) crack before the wood does.

I would put the tub in and watch the floor below and see how it acts. Actually this is what I did when we filled up a birthing tub in my bedroom.

Also neversummer's idea of having 1600 to 2000 lbs of people jumping and dancing in your bedroom....make sure you get a video.
posted by psycho-alchemy at 1:01 AM on December 28, 2011

Is the tub's bottom a completely flat 5'-diameter circle, or does it rest on legs or anything else that would concentrate the force on a small area?
posted by A Thousand Baited Hooks at 1:19 AM on December 28, 2011

In practical terms (now that I think about it), it's a water-filled bag in a foam-rubber frame. So it can be viewed as a completely flat 5'-diameter circle.
posted by Maximian at 1:24 AM on December 28, 2011

This is similar to the weight of a waterbed, which most houses can handle. Without knowing the length, height and spacing of the floor joists, we can't say for sure. If it did cause a problem, that problem would probably be slight damage to the plaster or drywall of the ceiling below. A leak would be a bigger problem. Chances of catastrophic structural collapse are probably near zero.
posted by jon1270 at 2:11 AM on December 28, 2011

I think the bigger question to ask is how you'll empty it out once it's filled.
posted by essexjan at 2:37 AM on December 28, 2011 [1 favorite]

Presumably it can be siphoned out the window; he's on the second floor, after all.
posted by jrockway at 2:46 AM on December 28, 2011

People having babies do this quite regularly. In fact, the capacity you mention is exactly the size of this pool. I wouldn't think twice about it but if you are concerned, call or email a birthing pool company with your question and ask?
posted by DarlingBri at 4:27 AM on December 28, 2011 [1 favorite]

There's no way anyone here has enough information to answer your question. We can make assumptions about generic houses, but there's no way to know if your house is overbuilt or underbuilt, much less know if some previous owner removed a supporting wall that now weakens your floor, or added a beam that makes this not a big deal.

I think your smartest move would be to pay for an hour of someone's time to get a professional answer to this question, since the cost of collapsing your floor would be expensive. You should bring in a structural engineer to give you a science-based answer, but personally I'd be tempted to just bring in a very experienced contractor and get his professional judgment on how the floor was constructed and how much load it could take.
posted by Forktine at 6:34 AM on December 28, 2011 [1 favorite]

This is similar to the weight of a waterbed, which most houses can handle.

5' diameter = 19 square feet. A Queen sized bed is 5x6.5 feet, or 32.5 square feet -- about 60% more area. A king sized bed (6.33'x6.66') is 42 square feet, so the load from the tub would be twice that of the waterbed, assuming the exact same weight.

Forktine *nails* it: "There's no way anyone here has enough information to answer your question." I don't know your house -- and I'm loathe to suggest that a 73 lbs/ft-sq load (1400lbs, 19 sq.ft) is safe without knowing it, so I won't.
posted by eriko at 6:47 AM on December 28, 2011

Chances of catastrophic structural collapse are probably near zero.

I guess I'll be the lone voice of caution. The consequences of catastrophic structural collapse, should it occur, would be severe injury or death and extremely costly repairs and medical bills.

No one is qualified to answer this question for you over the internet. There are too many questions about your house and its construction.

I very carefully considered where to put a fish tank in our house by examining structural floor joists, where load-bearing walls intersected, how the first floor was supported, etc.,

There's no simple answer.
posted by odinsdream at 7:13 AM on December 28, 2011 [2 favorites]

How deep would it be? A waterbed is like six inches deep, spread over a large area. This tub would likely be deeper than that, so the weight would be spread over a smaller area.

If I was insistent on doing this myself, I'd go down into the basement and figure out how the building is supported, and make sure the pool is located near a support. I'd stand in the middle of the room and have someone jump up and down. If I felt any bounce, I'd bail on the project. I'd also probably set up a couple of measuring sticks in the center of the room to measure the floor's deflection. One stick attached to the ceiling pointing down, one attached to the floor pointing up, and then put marks that line up with both of them. Then I'd start filling the tub. If I started noticing the marks moving more than say 1/8 of an inch, I'd bail on the project.

Perhaps relevant comparison: I needed to change an engine on a car one time. I built an a-frame hoist out of wood. The beam was two 2x6 screwed together and about 6 feet long, I think. I thought I had everything disconnected and started to lift the engine. I was incorrect and found that I'd lifted the entire front of the car off the ground. Curious, I got on a ladder and checked the deflection of the beam. There was no visible deflection.

So that bodes well for your project. Where I would be worried is in exposing some hidden flaw in construction. It isn't out of the question that there could be a joist or two in your floor that has holes cut into it for plumbing/hvac that weaken it. Or the joist is a little short and not resting adequately on its bearing wall, or that a joist hanger has gotten insecure over time.

In other words, I'd wager that the house *should* be able to support it just fine. But losing that bet means a LOT of damage.
posted by gjc at 8:12 AM on December 28, 2011

To build on gjc's suggestion: when you're downstairs seeing if someone jumping upstairs produces any bounce? Attach a small weight on a string that's at least two feet long to the ceiling underneath where the upstairs person will be doing that jumping. Any swinging by that weight will provide visual evidence of floor movement.
posted by easily confused at 8:34 AM on December 28, 2011

You should do a detailed underfloor survey. I have seen quite deep notches cut in joists to accomodate central heating pipework, this would change the load bearing properties of that bit of floor quite markedly.

Also the load is spread across 4 feet, not evenly distributed as under a waterbed

Could you place the tub on a wooden planks or similar in order to improve load spreading?
posted by epo at 8:43 AM on December 28, 2011

Ah, I just thought of another solution. I've seen this on Ask This Old House. They needed to cut a hole into a load bearing wall, and the structure was going to be unsupported until they installed the needed header.

What they did was create temporary supports. They put a 2x6 on the floor, perpendicular to the run of the joists. They then lifted another 2x6 to the ceiling and put in some 2x4s in an a-frame configuration, and squeezed them together to put tension on them. The 2x4s were basically pushing up and down. Nothing was screwed into the structure, it was just held together with tension, and toe-nailed into itself. Two of these setups under your pool should be more than fine, I'd bet. A drawing!
posted by gjc at 8:57 AM on December 28, 2011

Is there a reason the tub can't be placed in the basement? Maybe not as nice, but much lower chance of destroying your house.

If not, Forktine nails it; an hour of professional help could save you the cost of a potential structural collapse.
posted by Homeboy Trouble at 10:26 AM on December 28, 2011

Thanks for the responses so far. It does seem like people do this all the time and have no problems, but at the same time it seems like a lot of weight to suddenly add to the floor.

You should bring in a structural engineer to give you a science-based answer, but personally I'd be tempted to just bring in a very experienced contractor and get his professional judgment on how the floor was constructed and how much load it could take.

This seems like a good idea to me, but how would I go about finding such a person?
posted by Maximian at 11:42 AM on December 28, 2011

This seems like a good idea to me, but how would I go about finding such a person?

The same way you'd find a contractor to do structural remodeling work -- ask your friends, people at work, etc, and get recommendations of guys (note sexist assumption; I am sure there are female contractors out there but I've never yet met one personally) that have done good work for them. Then call the contractor and offer to pay for an hour of their time (or a case of beer, a gift certificate to a nice restaurant, whatever seems appropriate) to give you their professional opinion. If they think some temporary bracing is needed (which I think is probably a great idea), it would be polite to hire them for the job rather than hire your unskilled and underemployed brother in law, obviously.

Ideally you are looking for a small-scale general contractor, someone with a truck or two and maybe a small crew, who does additions and remodeling work, and who has seen all the weird ways that houses are constructed and modified.
posted by Forktine at 2:22 PM on December 28, 2011

eriko writes "5' diameter = 19 square feet. A Queen sized bed is 5x6.5 feet, or 32.5 square feet -- about 60% more area. A king sized bed (6.33'x6.66') is 42 square feet, so the load from the tub would be twice that of the waterbed, assuming the exact same weight. "

A queen size (or king size for that matter I'm guessing) has a more concentrated load because the mattress generally over hangs the base by a substantial amount. A 5x6.5' matteress might only sit on a 4X5.5' base, or even less.

Maximian writes "This seems like a good idea to me, but how would I go about finding such a person?"

You can generally get a list of licenced contractors from either your chamber of commerce or your municipality. Phone a few of those numbers and get some quotes. Be prepared to pay for an hour's time for what'll appear to be 5 minutes work as it is expertise you are paying for rather than labour.

Alternatively you could phone home inspection companies.
posted by Mitheral at 5:10 PM on December 28, 2011

All this discussion of waterbeds made me curious; it seems that a waterbed might weigh up to 2000 pounds, or about 50 pounds per square foot. In your case, you are talking about an area of about 20 sq ft and 1400 pounds, or about 70 pounds per square foot.

Again, whether or not something with about 1.5 times the load of a waterbed is a problem is not something anyone can answer on the internet.
posted by Forktine at 10:09 PM on December 28, 2011