Best Practices for Patio/slab beneath new hot tub?
June 19, 2021 8:53 AM   Subscribe

We just bought our first hot tub - yay! But now we have to figure out exactly what kind of slab to put it on top of. Advice appreciated, and more details inside!

We have been planning to build a patio (flagstone, probably) so assumed we'd just put it on top of that. But then friends told us to make sure we have a concrete slab poured first. But when we called the flagstone stonemason guy he said concrete is really expensive right now/hard to get into our location, and the hot tub would be fine just on flagstone laid out on a packed dirt slab instead.

1. Is that right?
2. If we have our flagstone patio on packed dirt, won't weeds grow up in between the flagstones? I've heard weed barriers don't work that well.
3. Is there any other material we should consider for the hot tub slab that's an alternative to concrete?

Thank you!
posted by egeanin to Home & Garden (6 answers total) 2 users marked this as a favorite
A lot of this depends on how much rain you get and whether or not it freezes in the winter where you are.
posted by mhoye at 9:55 AM on June 19, 2021

Best answer: I've installed or been involved with the install of dozens of hot tubs. We routinely installed them on wood decks. Properly installed flag stones are fine.

Hot tubs are a lot of weight but it isn't concentrated and they are forgiving of support surfaces that aren't perfectly flat or level.
posted by Mitheral at 10:25 AM on June 19, 2021

Best answer: As for alternatives you could just use gravel contained by pressure treated wood box or your flag stones.

However when your spa needs replacement (or you just get tired of it) you may not be able to get one /may not want one the same size and you may find getting the exact same flag stones difficult. IMO not really worth the hassle of dealing with two different surfaces unless you have a huge swim spa or something.
posted by Mitheral at 10:30 AM on June 19, 2021 [1 favorite]

Best answer: Heavy duty fiber landscape fabric works great as weed cloth, as long as you don't leave gaps and use a large overlap at joins. The plastic weed barrier isn't as good, aggressive weeds like Bermudagrass will stab right through it.
posted by agentofselection at 10:54 AM on June 19, 2021

Best answer: Mine is just sitting on dirt (came with the house—not my install). It isn't level to the tune of over an 1" of height difference on either side. I highly recommend having someone pour a concrete slab and making sure it's level. I got a quote for a whole new setup from a local hot tub place and they included pouring the slab as part of the install.
posted by jeffamaphone at 6:42 PM on June 19, 2021

Response by poster: re: question of rain -- we get lots of rain in the shoulder seasons and lots of snow in the winter.
posted by egeanin at 9:54 PM on June 19, 2021

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