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markley 08-03-2009 07:47 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?
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)? Also, it is a covered deck that the tub is going on, so the dirt underneath never gets wet.
Any suggestions/recommendations would be appreciated!

Scuba_Dave 08-03-2009 08:47 PM

I'd cut that section of deck out
Dig & pour a cement pad
Put the tub on the cement pad on the ground
Put a piece of lattice up on the side for privacy
Pour the pad so that the 1st step in the tub is even with the deck
IE - the top tub sticks up out of the deck about 12"
Mine is just a little low
But being lower means more privacy :wink:

Gary in WA 08-03-2009 10:02 PM

If you pour a slab, are you in a frost heave area?

What size is the pier under the post at the hot tub end?

Is the block wall filled or solid, the ledger is attached to?

Are the fasteners at the ledger through-bolts?

If a window is within 5' of the tub, like in Dave's picture, it has to be safety glazed.

If dropped, will the pump access panel still be accessible?

Be safe, G

markley 08-04-2009 07:02 AM

Well, I really do not want to cut out the deck and pour a slab. I only plan on living in this house another two years, and would like to take the tub with me. The pier under post at the hot tub end is 6x6. As far as the block wall being filled or solid, I'm not really sure. And yes, the fasteners at the ledger are through-bolts. Also, I do have a window that will be within 5' of the tub. What is safety glazed? Is this hard to do?
Thanks for the replies

markley 08-04-2009 07:03 AM

Oh, and i am in western NC.

markley 08-04-2009 02:55 PM

Any more suggestions out there?

Scuba_Dave 08-04-2009 03:09 PM

You have 70 psf with the hot tub alone
At 100 psf a 2x10 will span approx 9' 4" & you have a span of 12'
Unfortunately this is beyond normal span calcs - at least for me
I can't say if the 4x4's would work over a span of 7'

markley 08-04-2009 03:21 PM

What if I added 2x10 joists in between the existing ones in the area under the tub, then did (2) 4x4 posts with 4x4 beam on top of posts (supporting the joists) along each edge of tub.

concretemasonry 08-04-2009 03:26 PM

Your tub will weigh more with people in it and others nearby. A 4x4 as abeam/joist really does not have much extra strength.

Ledger supports are always questionable means of support because many use lag bolts. Even with trough bolts, make sure the spacing is adequate.

markley 08-04-2009 03:32 PM

I figured the ledger is a questionable means of support, which is why i want to install extra supports near where it is attached, as well as on other side of tub. What if I were to use 4x6's in place of the 4x4's?

markley 08-04-2009 04:42 PM

I just realized that the ledger is actually through bolted to the 2x10?12? wood on the first floor level of the house. Not sure if this changes anything.

Gary in WA 08-04-2009 10:10 PM

Safety glazing is tempering done at a window manufacturing company. When someone falls against it by accident, it shatters into small pieces, not large shards like when you break a mirror. (Auto glass is safety glass you've seen on the street)

Your hot tub would require an engineer to figure: the spacing of the new through-bolts; the larger pier and depth required, the beams needed-acting as joists; and the additional pier needed close to the other near the hot tub end.

THE EXISTING HOUSE FOUNDATION. There are a lot of things to consider that a Structural Engineer would know and be liable for. You don't want this liability, I don't want this liability, I doubt your Homeowners Insurance would cover any claim unless designed, permitted and inspected by your local Building Department. Let us know what he figured, I'm guessing some 6x10's, plus intermediate piers 24"x 10" and add some piers under the existing beam. You are talking about 3500-4500 lbs.

Be safe, G

concretemasonry 08-04-2009 10:28 PM

The bolts spacing it is dictated by traditional framing that usually works for a deck, but could be caught by an inspector. Now is the time to beef up the connection and get a permit and final approval for when you go to sell.

The ledger problems are very common and something that even a home inspector should spot that when he is hired by a buyer (pre-sale inspection) that puts you in a bad bargaining position. That is reason many sellers get an inspection (pre-listing) that the pay for it and do not have to publicaly reveal it and gives them a chance to get things right ahead of time.

Even a 2x6 will deflect less than a 4x4 because of the depth. A 2x10 will cut the bounce and deflection down further. - The code is just the worst you can build and still be legal, but there are ways an engineer can get around the arbitrary prescriptive requirements, especially because code for deck can vary widely because of local conditions since it is not the same as home the really interior and affected by the weather.

Around here, a post 2' from the home on a separate post footing can be used to support a beam that has joist cantilever to the house, but not touching is used to separate the deck from the house and the moisture problems a ledger is notorious for.

It is good you are looking ahead.

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