Deck reconstruction with hot tub


  #1  
Old 06-15-03, 03:02 PM
mike_and_kelli
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Deck reconstruction with hot tub

Three years ago, we refinished our deck and placed a hot tub on it. The hot tub dealer assured us that there wouldn't be a problem. But now the finish is wearing off, and the new lower-maintenance decking materials sounds like a good investment.

While we haven't noticed any problems from the added weight of the hot tub, plain paranoia suggests that if we replace the decking, we should also add additional support for the tub.

Currently, the joists are 24" apart, which as I've been doing research, is probably not enough. The deck is attached to the house, and the beam is apparantly set on pier blocks. The deck is only about 18" off the ground, so I can only look under the deck, not actually inspect it.

One plan I saw suggested adding an additional set of beams underneath the tub to add support. Could I use pier blocks here as well, or should I pour and dig concrete footings here. Or could I get away with those pier blocks that you can just set the joist on?

Also, I've read both positive and negative comments about the new composite decking materials on here. Would a material like Trex be okay to set a hot tub on top of, assuming that you have enough support underneath? I've looked at the fire resistance ratings, and Trex seems to be the best of the brands available locally.
 
  #2  
Old 06-15-03, 06:36 PM
L
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Welcome to the forums of DoItYourself.com.

First, how large is the deck? How large is the tub? How far is the beam from the wall of the house? What size of beam, and what size of joists were used to construct the deck? Once we know the answers to those questions, then we can determine if an additional beam is needed. (Use the "Reply" button -- that will keep everything in the same thread.)

Next, your joist spacing would have to be reduced for many of the composites to work on your existing deck. Simply add an additional joist centered between each of the existing.

Going to a composite would eliminate the need for sealing and staining, but you will still have to clean the deck on a regular basis. That can be done with the tub in place.
 
  #3  
Old 06-15-03, 06:44 PM
98lbwuss
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if you are going to use trex or a composite, get a sample and set it out in the sun next to your deck for an afternoon. You won't want anything to do with it after that. The stuff is a joke that will scald your feet if you don't hose down your deck every time you want to use it. We put it on a house and now we wished we had not.
 
  #4  
Old 06-16-03, 07:51 PM
mike_and_kelli
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The deck is 24' long and 17' out from the house. The beam is approximately 12' out from the house. (Tough to measure due to all of the landscaping, plus it's only a foot off the ground.) The beam appears to be a 6"x6", and is supported with footings about every 6 feet.

The tub is 6' x 6' and is located at one end of the deck; about 6' away from the house and about 5' from the edge of the deck. The beam runs about a foot or so just beyond the tub.

I finally found the plans from the previous owner who built the deck, and the pier footings are actually set on 42" deep concrete footings - so I now know how deep to set any additional footings I set.
 
  #5  
Old 06-16-03, 11:33 PM
L
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So if the deck projects out 17' from the house and the beam is set at 12' out from the house, the deck has a 5' cantilever from the beam to the outside edge of the deck? And the joists are spanning 12' from the house to the beam?

Sounds to me like you need to set 2 beams!

First, because of the tub being placed on the deck, you really need an additional beam about 6' from the house, at least in the area where the tub sits. Even if the joists are 2X12's, at 24" O.C., that 12' span is really pushing it without the tub. WITH the tub, it's overspanned.

And a 5' cantilever?? Hmmm... dimensional lumber has a cantilever limit of 24" -- anything more than that is over doing it.

42" deep footings -- obviously frost must be an issue. There is no other reason for a footing like like under a deck.

A 6X6 beam is overkill. (But then, so are 2X12 joists!)

If you need a 42" deep footing for frost, then that is what you will be digging. The beam you need to install between the house and the existing beam can be a 4X6, set on 4X4 posts, at about 5' apart. About a foot, but no more than 24" in from the outside edge of the deck, you need to set another beam the entire width (24') of the deck.

If you go with a composite for the decking, you will need to add a joist between each of the existing joists. Those can be 2X6's, once you have the additional beams in place. Simply block from the beams to the bottom of the new joists. (A 6" 2X4 under the joist, and a 11" 2X4 on either side of the joist, all screwed together. MUCH cheaper that a bunch of 2X12 joists, and just as strong, with the new beams in place!!)
 
  #6  
Old 06-18-03, 05:59 PM
mike_and_kelli
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Along the outside of the deck is a 8' high privacy fence with 4"x4" posts set on footings as well. Since I really can't get under the deck, I'm not sure how it is fastened to the deck, but my guess is that those footings are providing some support.

The way I see it, if I add another beam across the deck, then add another support underneath the deck, I should be fine. (Not to mention adding joists so that there is support every 12")

With the support provided underneath, should I be concerned about the decking underneath the tub? Will a composite such as Trex be acceptable?
 
 

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