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Category: Structural Engineering
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Experience:  Structural Engineer
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# pine 2x10 floor joists...I think 16 on center...how much weight

pine 2x10 floor joists...I think 16 on center...how much weight can they support? Does it matter if 1st or second floor? E.g. I want to put a larger soaking tub in the master bath. Do I need to be concerned? Also, I've had 20 or more people in my kitchen & eating area before during a party. Is that dangerous? That's like driving my suburban into my kitchen, surprised it hasn't caved in the house.

StructuralEng : Hi
StructuralEng : I can help you with this. Give me a few minutes to read the question complety
Customer:

Customer:

so give me enough details to be comfortable but please don't make me do the math :)

StructuralEng : No problem.
StructuralEng : What is the length of the joists?
StructuralEng : Do you know I'd they're southern pine? Do you know the grade?
StructuralEng : If, not I'd.
Customer:

hmmm

Customer:

well, they're roughly 13 feet

StructuralEng : And where along the 13' span do you want to put the rub?
Customer:

scissor truss design, 2 story colonial,

Customer:

vaulted ceilings and such

StructuralEng : How far from the end?
Customer:

near the middle of the house

StructuralEng : Will the tub be oriented so the long dimension is perpendicular to the joists?
Customer:

so the house is split into two 13 foot halves essentially

Customer:

probably, but not necessarily

StructuralEng : Near the middle of the house is at the end of the joist span, correct? Near a bearing wall?
Customer:

the tub might be same length and depth

Customer:

larger soaking tub type thing

Customer:

yes, near the center load bearing wall

StructuralEng : I hope you done have 2x10's spanning 26' or else you have a much bigger problem on your hands.
Customer:

no, definitely pretty close together

Customer:

not 26' for sure

Customer:

oh

Customer:

you mean span

Customer:

sorry, no I've been in there

Customer:

I know they're split into two that overlap at the center load wall

Customer:

each side has it's own independent 13' span floor joists

Customer:

actually

Customer:

on the other side of the house there are no joists

StructuralEng : Ok. If they're going 13', then your 2x10's @ 16" o.c are fine for the tub, provided its near the end.
Customer:

open foyer

Customer:

Customer:

so it would be just replacing it with larger one

Customer:

Customer:

what about the 20 people in my kitchen?

Customer:

is that dangerous?

Customer:

because how can people have parties??

Customer:

if I do the math, that's literally like driving my suburban into the kitchen

StructuralEng : Also, I wouldn't worry about too many people in your kitchen or living room. Residential construction is typically 40 psf LL. if you have a 15' x 10' kitchen, that's 150*40 = 6000 pounds (evenly distributed, of course). That's easily 30 people who weigh 200 pounds each. Unlikely to happen in such a small space.
Customer:

close to 1.5 tons

Customer:

So, assuming the weight were distributed evenly, it actually would hold the suburban

StructuralEng : The difference between the truck and the people is that the people are spreading the load over a large area to all of te joists. A truck would load only 4 joists very heavily.
Customer:

funny

Customer:

so....how large a tub can I fit upstairs then?

Customer:

how heavy

Customer:

in terms of water volume weight

Customer:

and of course, there's a person in the tub, so add 200

Customer:

what you're telling me is....if I do the math

Customer:

40psf

StructuralEng : If its at the end of the span, and te long dimension of the tub is perpendicular to the joists, you can go up to 3'-6" wide. The end of that 3'-6" shouldn't extend any further than 4'-6" into the span of the joist.
Customer:

so if the tub is 5 x 4, e.g

Customer:

20 sf x 40psf = 800lbs

Customer:

why does joist position matter?

StructuralEng : The full tub will be higher than 40 psf. The reason it's ok is that it's at the end of the span (not contributing as much to bending, more to shear). Additionally, 2x10 pine joists spanning 13' is pretty robust for residential construction. I would typically see 2x8's spanning that length.
Customer:

definitely 2x10 and definitely 16 oc

Customer:

maybe less actually

Customer:

I can't remember exactly

Customer:

but I had the ceiling torn open at one point and they are definitely really close together

Customer:

I ran a few wires

Customer:

could barely fit my cordless drill between them

StructuralEng : If you've found my answer helpful, please "accept" it. I'll be happy to answer additional questions on the topic. If you could provide feedback, I would appreciate it.
Customer:

well, yes, I have

Customer:

thank you very much

StructuralEng, Consultant
Satisfied Customers: 6591
Experience: Structural Engineer
Customer: replied 4 years ago.
One thing I did not mention, which I think may be very important. On the second floor, above the load bearing wall, on the same side as the existing tub, is a hallway. Again, valuted ceilings, open foyer, so front half of house is all open, nothing resting on this section of the load wall, but back half has about a 3.5 foot wide upstairs hallway, behind which is the existing tub, so in reality, the tub is already more than 4 feet away from the load wall. Is this dangerous given the 16" on center 2x10 joists? ( I verified, definitely 16" on center). Again, scissor trusses, so no truss load on the hallway wall as I understand it.
It won't cause the floor to cave in, but could definitely result in excessive deflections and cracked finishes. I would add new joists between the existing for the extent of the tub.
Customer: replied 4 years ago.
What does that mean? I an add joists?? Between 16 on center joists? Is that even possible? What about all the wiring that's already in there? Is that even possible?

I have another option, but it will require some work. Either way is going to be a fair amount of work to get the numbers to check out on paper.

To add the joists, you'll have to cut the wires, pull them back and then add a junction box to reconnect everything. I know it's a pain, but we've had to do this before in residential applications.

Another option is to sister the existing joists with metal studs. This will make working around the existing wiring and plumbing much easier, but requires more engineering and detailing on my end. I can do this for an additional 40, if you're interested. Just let me know.

Customer: replied 4 years ago.
what do you mean an addtional 40?
I mean I'll do the analysis and sketches for a fix for a bonus of 40. This would be above the fee already paid.
Customer: replied 4 years ago.
Is there any alternative, like for example load sharing between the first and second floor with another wall right under the upstairs wall that then spreads the load between the first floor joists and the second floor joists? Or does it not work that way?
There could be, if that wall that's not at the end is load bearing, but I don't believe it is. If it were, then the joists below would not work, because they can't take the load of both floors.
Customer: replied 4 years ago.
interesting...so my house was constructed poorly, inspected along the way, and now I've got to remedy the poor construction. GREAT! So if I go ahead with the plans, how much would you expect I'm in for in terms of implementing the whole remedy? Given that they're 16 on center, I would suspect that the I need to do this for the length of the wall upstairs, which is about 22 feet long...really? Wow! Below that entire 22 feet is my kitchen, which has soffets for plumbing from the bathrooms above it. So, I would have to have someone come in and sister about 17 joists, which would include working around soffeting. Really?
No, the issue only exists where you want to put this heavier tub. You would only have to do it for the 5' extent of the tub, but the sisters will need to be full length. It's fine for typical loading, just not for a tub loading at that particular location.
Customer: replied 4 years ago.
So the hallway wall upstairs that is 3.5 feet from the end of the joists (scissor trusses remember) is fine then. Ok. So...when you talk about metal sisters for these 4 or 5 joists then I'm picturing something like the 9th picture from the bottom on this site: http://hall-house.blogspot.com/
I can't view that site right now. Will respond ASAP.
Customer: replied 4 years ago.
Ok, I also see this kind of synthetic material sistering out there, but seems like your idea of metal is the best because I can hopefully go around all the wiring up there. Also, if there were some piping that were in the way of the 5th joist for example, toward the end of the tub...would it be ok to just leave that one unsistered? In other words if I get the majority of the joists under the proposed tub sistered, is that "good enough"
Yes, it will be ok for the last one.
Customer: replied 4 years ago.
if they were actually closer together where the tub is when I open up the ceiling...would that make a difference? Say they're 14 or 12 on center there. Could that support the tub at 4 foot from the load wall?
12", maybe depending on species and grade. 14", definitely not
Customer: replied 4 years ago.
and on the cost to implement something like this? What (roughly, will not hold you to anything) am I looking at?

A couple hundred buck, tops........... if you do it yourself.

For a contractor - a few thousand.

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