Potential Problem With The Deck My Tub Sits On

[ne_skier]

I'm a bit scared to ask this but if I've got a looming problem I should at least be aware of it, if I can't fix it.

We had a deck built for our tub (by a very experienced builder). I'm not a builder but hopefully my explanation of the construction makes sense. The deck is ~18" above ground and ~12 x 12 ft. The tub is ~8 x 8 ft. The deck foundation is a 3 x 3 grid of concrete pillars. I dont remember the exact diameter of the pillars but Im pretty sure they're at least 12 in. There are 3 main beams running along 2 sides and down the center, seated on the pillars. The beams are composed of 3 or 4 2x10's sandwiched vertically together. There are individual 2x10's connecting the main beams at 16 inch spacing. AZEK decking is layed directly over the skeleton formed by the main & cross beams. The Azek decking is 1 in. thick x 5.5 in. wide. The tub sits on the Azek. To my unqualified eye, the foundation and beams are perfectly adequate.

My concern is the following. One side of the bottom of the tub's frame unfortunately lands almost midway between two cross beams; the Azek panels are largely supporting the load on that side of the frame, since it sits nearly in the center of the span between beams. The Azek panels directly under the two corners of this side are sagging a bit. Im certain they're sagging because I can see elevation difference between the two panels under the corners and the non-loaded panels directly adjacent. I haven't measured it with a caliper, but running my finger across the gap between the panels, it feels like 1/8 - 1/4 inch.

The opposite side of the tub frame lands directly over 2x10 cross beam and there's zero sag there.

My question is, how bad is this? Major problem? minor problem? Not really a problem?

I also find it interesting that only the Azek panels under the corners are sagging. The panels under the middle of that side of the base do not appear to be sagging, which suggest that the tub distributes all or most of it's load straight down the vertical corner members of the frame. If that's true, then I'm inclined to suspect that the only thing in the tub that might be getting unduly stressed due to the unevenness of the seating surface, would be the points where the horizontal members at the bottom of the tub frame join up to the vertical corner members. And also, I think the tub shell is probably not getting abnormally stressed from this.

I'd greatly appreciate people's thoughts on my situation and analysis here!

In hindsight I should've gotten the exact dimensions of the tub's base, determined exactly where it would sit on the deck and told the builder to ensure there were beams directly under the base sides. But I assumed (naively perhaps) that a tub frame would designed to distribute load very evenly.

At this point the only way I can envision fixing this is to move the tub when it's empty, rip up a few Azek panels, install extra beams under the corners and then reinstall the Azek.

Is it safe to slide an empty tub along a deck? Is that even possible? My tub's manual says it's 800 lb dry.

Thanks for reading!

[Dnepr Dave]

Pry the spa up with a big pry bar and slide some 1" schedule 40 pvc pipe cut a foot wider than the tub underneath it. If you have about six or seven pvc pipes, you can roll the spa to the side, taking the pipe from the back and moving it to the front of the tub as you go, kind of like how the ancient Egyptians moved blocks of stone for the pyramids.

You could even tip the spa on its side, off of the deck, while you do your repairs. It won't hurt the spa.

Dave

[ne_skier]

The pipes are an interesting idea; I would not have thought of that.

Tip the spa on its side > Seriously???

It occurs to me that disconnecting the power line is probably a good idea, if not necessary, if I decide to try this.

[Dr. Spa]

Lots of spas are transported on their sides............. Seriously !!!

[Spa_Guru]

The vast majority of spas have to go thru 44" gates to even get them in a back yard, so yes, tipping them on the side is commonly done.

I usually put down some carpet first to keep from scarring the acrylic or the panels.