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markley 08-02-2009 04:02 PM

How much reinforcement needed?
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Hi all. First off, I am new to this forum. Thanks in advance for any advice/suggestions you may have. I am going to put a hot tub on my existing deck. The hot tub is fairly small (62"x83" and 2450 lbs full). I have attached a diagram of my deck construction. I would like to place the deck in the lower left corner of the deck (next to house). The only support along the house is a 2x10 ledger anchored every 16 inches to a block wall. One problem i can already imagine is digging footer for any extra support posts. The height of the deck is only about 2.5 feet where i'd like to put the tub. Any recommendations on how to dig a hole in tight quarters? Or is there an alternative for a footer? I was thinking of running (2) 4x4 beams perpendicular to the joists (one along each edge of tub) supported by 4x4 posts on a footer. Would this be sufficient?
Any suggestions/recommendations would be appreciated!

markley 08-03-2009 03:55 PM

I have a few more things to add to this. The hot tub dealer says that the joist spacing required is 12" o.c. As stated above, mine are 16" o.c.. Could I just double up the joists under the area where the hot tub will be? Or should I just put one in between the existing joists (making them 8" o.c.)?
And regarding the footers for support beams, could I just set 4x4 posts on dekblocks (maybe bury some and level)?

thedeckbarn 01-09-2010 05:36 PM

The support for a deck is from the post under neath it. Each 5 gallons of water weighs about 65lbs. If I was doing your job you would get 2 more rows of posts and beams underneath the space where the tub is. What makes a deck sag is the weight applied to the footing pad under the post. The greater the area of the footing pad the more supprt you will have. you have to think of it as a single post with 5,000 pounds on it is like a needle into the ground. There is no mass to stop the penetration of the post into the ground. The more post, with footings you have applied over an area the less sinking into the grouind you will have. Generaly a 12" diameter pad 10" thick will do the job for each individual post.
To see what happens to improperly supported decks go to
steve scholl

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