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StructuralEng, Consultant
Category: Structural Engineering
Satisfied Customers: 7000
Experience:  Structural Engineer
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I am trying to determine the weight capacity of my outdoor

Customer Question

I am trying to determine the weight capacity of my outdoor deck for a hot tub.
Tub = 7.5'x7'= 52sqft 6500lb loaded and people
Deck = 10ft joist span + 2ft cantilever
2x10x12 joist, 16" o.c.
4x4 post spaced 6' apart at 10ft from house
Single beam at 10ft 2x12?
do I need more reinforcement
Submitted: 1 year ago.
Category: Structural Engineering
Expert:  StructuralEng replied 1 year ago.

Hello. Does the hot tub load the deck at the four walls only?

Customer: replied 1 year ago.
The deck is 12' x 40'. The spa will occupy the first 10 feet of the deck (2' border area. Surrounding it) two of the corners of the spa will load directly on the posts.
Does that answer your question?
Expert:  StructuralEng replied 1 year ago.

I will assume it loads the deck at the walls only.

Customer: replied 1 year ago.
I am not sure I understand the question. The deck is 12'x40' with the spacing and spans as listed. The spa is 8'x7'. It will be centered (the 8' part) witchin the 12' of deck. The width will occupy 7' of the 40'. Located 2' from the end. I would say it is loading the part attached to the house. And the first 2 posts. One edge will be located directly above the two posts. The part closest to the house will be located 2' from the house over the joists only. The remaining 31' of deck will have only light loading.
Expert:  StructuralEng replied 1 year ago.

2x10 are too small to span 12' supporting the tub. You should use 2x12 under the are with the tub and triple the two that are directly below the hot tub walls and parallel.

Customer: replied 1 year ago.
As in the first post the span is 10' not 12'. The beam is located 10' from the house wall (ledger). There is a 2' cantilever of which non of the tub will be contacting.
Customer: replied 1 year ago.
Sorry I meant joist span not post. Joist span is 10' 16"oc. Beam is (2) 2x12. Posts are 6' apart at 10' from the ledger. Hence a 10' joist span.
Expert:  StructuralEng replied 1 year ago.

Then you can double the 2x10s directly under the walls of the hot tub

Customer: replied 1 year ago.
Can or must? Can you estimate what is the max load in psf given the information I have given you?
Expert:  StructuralEng replied 1 year ago.

A psf load rating is not meaningful because the hot tub doesn't load the deck uniformly. It loads it with four line loads. You must double those joists

Expert:  StructuralEng replied 1 year ago.

Hello. Do you have any other questions on this topic? If you could rate my answer, I would appreciate it.

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