Framing and foundation for hot tub?
My step-father and I have built a deck and it has come out much better than we expected – mostly due to the content on this website and some help from people responding to my post earlier. Still some work to do but the next step is to build a foundation for the hot tub to sit on which they want to sit beside the deck.
The layout of their backyard is setting up the hot tub to be about 10-12″ off ground level. Does anyone have any recommendations on framing/building a foundation for a hot tub? I understand the normal span tables only consider so much typical live load/dead load. I was thinking we could put 4 footers with (2) 2×10 beams and 2×10 joists maybe 12″ OC. The hot tub has a capacity of 420gal (3500lbs) plus the weight of the tub itself (about 1000lbs). The entire hot tub is 91×91 so I can’t imagine a joist would deflect an excessive amount over 8′. Also, I see these hot tub bases people put down – could I possibly use this as a subfloor to help spread the weight along the joists (as Patrick was stating in the most recent podcast with the tub+cut joist)? I assume the plastic/polymer base would be great in a wet environment and help keep the PT beams/joists dry in this application.
Thanks for any info you can provide.
Replies
Hey guys, My name is Jason, I am new here and am hoping to get some feedback on my plans to place my beachcomber hot tub.
I will be putting the hot tub outside - wiring is all set but I am going back and forth on the base. I live in a VERY sandy area and my yard rarely ever shifts. I have plenty of things to prove it, including my deck and a motorcycle shed and none of them have moved at all over the last several years. The garage foundation is uncracked and still level as well.
I prefer to avoid a concrete slab for the hot tub as that will require jumping through permitting hoops. To that end I checked with the manufacturer who stated that the tub can be put on a crushed gravel base without any problems at least as far as they are concerned and that doing so is one of their recommendations.
I had thought to dig down into the sandy soil about 6 - 8" and put down weed blocker fabric and then edge the hole with pressure treated or railway ties and fill it with shurpak or some other form of crushed gravel compacted with a compacter and topped by 24"x24" concrete pavers with the tub on top.
My question is multi-part (and I appreciate the help). First would shurpak be too dense? I was concerned that perhaps I need gravel that is better at allowing water through then shurpak. Secondly, does anyone here have experience with bases like this? I read through a lot of comments in the forums here with a lot of people saying they were going to do it but no follow-up on how things worked out that I could find. I would of course never try this on clay filled soil!
Lastly.... not to use up everyone's question answering patience.... :) I do have a pt 8'x8' platform I made to transport the tub. It is made of 2"x6" pt stringers 12" on center with 2"x6" decking. I contemplated setting this directly on the pavers with the tub on top but was unsure if this would be wise. The thought behind doing that was that if anything did shift the wooden platform would help bear up some of the load a little more evenly. I know 2"x6" is not sufficient if I tried to just support it off the ground but figured if the stringers are sitting on the pavers and supported their entire span it would be fine.
Any useful input is very much appreciated :)
Thanks!