Deck Span - For Hot Tub

Started by Jim2017, June 15, 2017, 01:06:23 PM

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Jim2017

Hi, I hope it's ok to ask a deck related question.  After Googling weight limits on joists, I was pointed to this site several times.  Hope someone can help.

I read a number of the posts on similar topics.  Can you double check my assumptions and call out any issues you see?

The hot tubs I've been researching suggest that I build a deck strong enough to handle 5000 lbs over an 8' x 8' area.

I plan to build the support structure in the following manner.
1. Attach a 2 x 10 x 16 PT ledger board to the house using 3/8" x 3 1/2" lag screws
2. That is 2 lag screws every 16" OC
3. Add joist hangers every 16" OC
4. I went to the AWC Spac Calc as many on this forum have suggested: Species (Douglas Fir-Larch; I think this is the common pressure treated species for the average lumber yard); Size (2x10); Grade (No. 1; again, i think this is typical); Member Type (Floor); Deflection Type (no idea, i left it at L/360); Spacing (16); Wet Service Condition (Yes), Incised (No); Live Load (5000 lbs / (8 x 8) = 78, so I chose 80 psf); Dead Load (dunno, left it at 10 psf)
5. hit the button: 12' 3"
6. I wasn't initially planning on a hot tub, so my joists will be resting on (2) 2x10s set on the shoulders of 6 x 6's which are sitting on 12" diameter by 42" deep pads spaced 6' apart.  My joist span is 11' 10"

Whew.  Am I ok or do I need to rethink this.  Any feedback is welcome.
Jim

Don_P

If you are out west then treated, incised, dougfir is pretty standard, #2 would be more standard but #1 is available. East coast SYPine is more common, not incised, #2 commonly available, #1 by request.

A drawing would help. How large is the deck? Where is the hot tub on the deck? I'm assuming there is a walking area and human load and the hot tub is acting as a non-uniform load acting on the joist and girders. Can you post under the ledger at the house, hanging by lags with this load is not a great idea. Can you put posts under the tub area itself?


ChugiakTinkerer

Have you checked out the IRC or the AWC Guide to Decks?

If you have to attach to the house, through-bolting the ledger board is preferable to lag screws.  Is that feasible with your house?

EDIT: You don't mention the size of the hot tub, so I looked at specs for an 8-person.   Holds 542 gallons (4336 lbs), 8 people (~1600 lbs), and itself weighs probably 500+ lbs.  Add in the dead load for the deck and your 9x8 area may have a load of 7,000 lbs.  A smaller tub will certainly weigh less but in calculations like this it does not serve you well to underestimate the load.
My cabin build thread: Alaskan remote 16x28 1.5 story