Reinforcing deck for hot tub


Old 08-30-15, 08:57 AM
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Reinforcing deck for hot tub

I have a new deck that is built low to the ground, about 12 inches above grade.

The joist are 2 x 8 pressure-treated, 16" o.c., with cedar decking on top.

The structure is supported by concrete deck blocks under joists on the exterior edge and in the middle of the deck, and with the ledger board on the house side.

One in every third joist sits on blocks. There are no posts or beams. All the weight is on the joists.

I want to put a 5,000 lbs hot tub on one side of the deck and need to reinforce to get it to at least 100 psf. Clearly, what I have now isn't enough.

My plan is to pull up the deck boards and put in more 2 x 8s between the existing joists under where we plan to put the tub.

Each of these new joists will sit on two concrete deck blocks but they won't span the full widths of the deck.

To keep the joists from shifting under load, I would block them in with 2 x 8 to the existing joists.

So, I'd end up with an 8' x 8' section of the deck of 2" x 8" joists, 8" o.c. and at least 12 pier blocks.

Does this sound like it would work? I'd rather not tear apart the deck and start over.

Any suggestions or comments appreciated.
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Old 08-30-15, 09:08 AM
Join Date: Jan 2011
Location: USA
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Sorry to say but your deck was not built right in the first place.
There should have been footings set below the frost line.
Pier blocks are going to move up and down and never stay even.
What size is the ledger boards, single or doubled?
How big is this deck?
Pictures so we can see what your seeing is always nice.
Old 08-30-15, 06:14 PM
Join Date: Sep 2009
Location: Louisville KY
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Following up on what Joe said, to start by getting a solid base under that deck! The more weight you put on top of it the more weight you're going to have on the small area you have resting on the ground. If it's not supported firmly on the ground with footings that are below the frost line and of sufficient diameter you're never going to be able to make the deck substantial enough to support the weight you are talking about

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