Getting a hot tub. Questions about my deck...

[mark02tj]

After many years, I'm finally giving in to SWMBO and agreed to a hot tub. Not getting a big one - just a two seater. You can see it here.

This thing only holds 140 gallons, so it's relatively "light" compared to a lot of the other 4 and 6 seat models. According to the spec, it weighs 526 lbs empty and 2044 lbs full. I'm assuming that's including occupants since 140 gallons of water weighs somewhere around 1200 lbs.

My question is about my deck. The spa company sent a "technician" out to do a "site check" and he said the deck was OK. I asked "Do you want to go around to the walk out to take a look underneath the deck?" He said "No" and jumped up and down a couple of times and said "this deck is pretty solid. You should see some of the other ones out there." Not very scientific... or comforting to me. :confused2:

The deck is attached to the house with lag screws. I don't know how deep they go, but I'm assuming they go in pretty deep to the sill. It's framed with 2x8's that span 10 feet. There are joist hangers on the both ends of the joists. I think the thing that concerns me a little is that the joists are 24" on center. I know that's probably standard (or at least to code), but it still concerns me a little.

Should I delay the delivery/installation of the tub for a few days and install some extra joists between the existing joists or will the 24" spacing be OK?

As an aside - do you guys with hot tubs use them a lot? She used to have one and said she's probably use this one 3-5 times a week. It will be right outside our bedroom door on the deck, so it will be handy.

THANKS in advance to the many (many, many!!) TBNer's that are much more knowledgeable about such things than I. :thumbsup:

 

[mbohuntr]

I would take up the deck under the proposed spot and sink some concrete filled sonotube below the frost line, and run some 2 x 10's across the joists on both sides of the tub, and add a couple of extra joists just to be absolutely sure. You don't want to find out it wasn't strong enough the hard way...., and the weight of the tub and water might be ok until you add in 10 more people for a party....

 

[sld]

We installed one last fall. I made a separate deck for it roughly 8x8. It is way overbuilt with 4 posts in the ground, another 5 posts on cement blocks and 2x6's on roughly 12-14" centers. Topped with 5/4" deck lumber. Like I said, way overkill.

The empty weight sounds a bit high for a 2 seater but find the footprint and figure the weight per square foot. You will be surprised it is probably not that much. Ours was around 70 lbs per square foot. If you think you need to, add another post or 2 on concrete blocks and reinforce it a little.

We are averaging about 2-3 times per week use. It has been nice once I got the hang of the chemical balancing act. We plan to drain and leave empty from May thru September. Others I know that keep them going year around end up not using them much in the heat and it just cuts your pump life in half.

 

[vtsnowedin]

My daughter has a six person one at her house she built on the back thirty. I helped build the deck under it. We built it **** for stout so as to not worry about it. My wife and daughters use it quite a bit,perhaps twice a week and more if somebody has strained something and needs to relax. Yours will probably weigh less then 1600 pounds when your sitting in it which isn't that much on a square foot basis. But you could before or after the tub arrives stick in stringers on twelve inch spacing in new joist hangers and have it beyond worrying about.

 

[mark02tj]

3 replies in less than 45 minutes! I love TBN!!

It's basically a triangular shape. The two equal sides are 5'-8.5" each. The formula for area of a right-triangle is (a*b)/2. Roughly (5.75*5.75) / 2 = 16.53 sq. ft. Spec says 2044 lbs loaded so 123.65 lbs/SqFt.

I should have described the deck a bit better. Putting in a new post or two isn't going to happen. The deck is over a walk out basement entrance so the "main framing" is what is going to stay.

So, I'm back to the question of - Should I put in extra stringers on joist hangers where it's going to sit or will I be OK?

THANKS!

 

[sld]

A picture would help. You may be able to add a couple of stringers and try and triangulate (think rafter design) some load to the nearest post or 2.

How far away from the posts your load is and what type of post used will make some difference. Even then, 125 lbs/ sqft is not all that much. For peace of mind you want it beyond a shadow of a doubt though.

 

[mark02tj]

Pics you need and pics you shall have!! :thumbsup:

From the side:


From the end: (Hot tub will go to the right of the upper door)


Close-ups of the framing below:

 

[mbohuntr]

I have a nephew that lives near Columbus. I noticed on his deck, that the outer rim was nailed onto the vertical posts. Not much load bearing there..., I'd check that, and bolt on jack studs if necessary, and at a minimum, add some extra joists. If your seeing some deflection with the tub installed, add a beam, and two jack posts.

 

[DKCDKC]

I'd worry a bit about the lag bolts. In a similar situation a few years ago we put some 2 X 6s bolted to the structure under the joist bolted to the home. It's as if it's resting on them and looks nice - used the spacing of the posts. And I'd double-up on the joists under the tub to supporting posts, etc. just for a more secure feeling at minimal costs. My own 6 person tub sinks a foot into the deck and rests on its own little deck supported by four 6X6 posts. I like it.

 

[kenmac]

IMO,, I would add some support post against the wall.. That rear is only screwed into the siding and doesn't really have any support ..Better safe than sorry..

I have a large HT.. Mine is on the concrete pad beneath the deck. (like where your lawnmower is stored