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
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?
Have you checked out the IRC or the AWC Guide to Decks (http://www.awc.org/pdf/codes-standards/publications/dca/AWC-DCA62012-DeckGuide-1405.pdf)?
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 (http://www.sunrisespas.com/files/2017SunriseSpecs-ParagonSeries-Medallion.pdf). 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.