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diplomat
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When the AHJ doesn't require an engineer for this, if I didn't have the BC calc software, I'd use regular span tables, and increase spacing and double joists as needed to get the added load of the tub.

Figure the size of the tub and the amount of water weight, and if you arrive at 160psf, you need 4x the amount of joists at the same span that would get you the regular 40psf.

Generally an engineered deck won't have as much wood though, it'll be shorter spans on the joists and beams.
 

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Discussion Starter · #3 ·
An 8 person tub with 550 gallons of water and 8 people weighing 185 comes in around 7000lbs and covers about 75sf. That load would be just under 100psf.

The deck is going on a double wide sitting on a block foundation. There is not a full rim joist to attach a ledger and the block looks a bit iffy (not sure if grouted). I think I'm going to build it self supporting with the ledger tied into the block.

I will play with some load calcs and see what my supplier comes up with on there software.
 

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Can't help much on the hot tub. One thing I wouldn't do is count on the double wide giving any support. Design it as a free standing deck.
 

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Talking Head
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This is one of those times when I would spec it as well as I could and then fork it over to an engineer for review. For a couple hundred I'll be able to sleep easy at night. If you leave it to the engineer to do everything then you're looking at a lot more money.
 

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Pro
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I built one with 6x6 posts on 4' centers on 18" round by 48" deep footing . 2x12 set on top of 6x6 with joists ( 2x10 )on 12" centers . It's was 4 foot high . With trex decking . Think it was done maybe tens years ago .
 

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Talking Head
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If they're going to put one in on a slab, after you've built the deck, then I'd recommend you don't worry about it too much(because it's not your problem) and mention that it's easier to get in and out if they're about 12-16" above the deck or have a grab rail somewhere to get in and out.

I did this one because the heights worked out with their existing patio but the step down in requires you to reach down and grab the edge when you're getting in. It's better to let the ladies get in first.:whistling
 

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Pro
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EthanB said:
If they're going to put one in on a slab, after you've built the deck, then I'd recommend you don't worry about it too much(because it's not your problem) and mention that it's easier to get in and out if they're about 12-16" above the deck or have a grab rail somewhere to get in and out. I did this one because the heights worked out with their existing patio but the step down in requires you to reach down and grab the edge when you're getting in. It's better to let the ladies get in first.:whistling
The thing with that is service of system . Changing pumps and jet fitting , hose cracking , lights . It so much harder to do with set in hot tubs .
 

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Custom cabinetry
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Here's what holds up my hot tub.
Double 8" joists, double 8" beam that rests on my foundation on 1 end and a 6x6 on the other end. The pier is 30" diameter but it's also picking up roof load.


Room Floor Building
 

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I built one for my aunt and uncle about 12 years ago.
I put all thread thru the foundation of the house
I used 2x12 12" on center for joists
I had 2 beams 3-2x12 on each end of the deck setting on on a total of 10-6x6 posts
I am not sure what the size is on the hot tub but you could easily fit like 7-8 people in it.
You don't need to hire an engineer to build a deck. just build it as massive as you can dream up. Normally where you use a 2x6 use a 2 x12 and normally 2' centers use12or6
Today we have access to span tables and all that I didn't have at the time just dive in
 

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Talking Head
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The thing with that is service of system . Changing pumps and jet fitting , hose cracking , lights . It so much harder to do with set in hot tubs .
A very good point I should have mentioned. On the tub install I linked above I held the framing back 5" from the tub and there was good access underneath the deck. Failing that I would have made an access panel in the decking. The techs did tell me that the newer tubs are light enough that they can drain them and lift them up to work on them if necessary but it adds a fair bit to the bill if the HO doesn't drain ahead of time.
 

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I doubt any building department it's going to allow you to put a tub on a deck without an engineer anyways.
Remember not everyone has a building department.

To limit your liability it is a good idea to have an engineer confirm the design, with or without someone telling you you have to. This is a case where I would do the design (as I usually do) and then send it over to the engineer. Cheap insurance and a nice pat on the back when I am right.

Remember the footings need to be appropriately sized and that the increased lateral loads need to be accounted for as well.
 
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