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Hot Tub Base

Discussion in 'Hardscaping' started by RToolin50, Nov 29, 2009.

  1. RToolin50

    RToolin50 LawnSite Member
    Messages: 5

    I am prepping a base for my hot tub. First I am placing a geotextile fabric, then 6" of compacted aggregate, then 1-2" of mason sand for leveling, then 16"x16" regular concrete blocks (cheap kind). The hot tub will go right on top of the concrete blocks. Does anyone with experience recommend using edge restraints or polymeric sand? Note: There will be an extra 3" on all sides of the tub to the edge of blocks. Thanks in advance for your help.
  2. StoneFaced

    StoneFaced LawnSite Member
    Messages: 201

    After the tub is set, what will be the finished product on the four sides of the tub? (raised deck, beds, lawn, patio, etc...)

    Assuming a few things: Stable ground, w/ top soil removed, not recently excavated sub soil (like an over dig), the stone base material is a good compacting stone (like a 304), and the area is not catching any water run off...sounds ok. In my area I like to use crushed limestone, a 304 base w/ a #9D or a #10 for finishing...as opposed to sand...if using sand...I try to keep it under .50" (but that's me).

    I would try to minimize the sand as much as possible, because sand displaces...especially in a freeze/thaw enviro., and when water is introduced, especially under vast amounts of pressure (hydrostatic).

    As for the edges, I always like to use a well restrained retainer, such as a treated timber for added strength and to minimize the possibility of any movement or wash out. What gets used is sometimes a decision based on the aesthetics and whether or not it will be seen.

    Polymeric sand, might be more of a judgement call based on a few things...might not be necessary but probably wouldn't hurt if you anticipate a lot of splashing, overflow, etc.
  3. DKJLawnCare

    DKJLawnCare LawnSite Member
    Messages: 139

    Not sure, but I think that most hot tubs recommend more than 3", I know our hot tub had to have a minimum of 12" on all sides. Just something to consider
  4. RToolin50

    RToolin50 LawnSite Member
    Messages: 5

    I'm sorry, I was bit vague on a few things. After the tub is in place, next spring I will be putting in a paver patio around the tub. However, as it goes, that will not be until next spring, and the tub is going in NOW.

    Water runoff will not be a problem in this area. So it sounds like I should keep the sand to between .5" and 1" before I place the concrete blocks. I plan to make the layer of sand flush with ground level, and then placethe concrete blocks on top of that. That is why I am wondering if an edge restraint is necessary. If I do the edge restraint, I will have to take it out next spring when installing the paver patio which will connect right to the hot tub base.

    When I was referring to the 3" around the tub, I meant that the hot tub actually measures 7'6" x 7'6", and I am making the base an even 8' x 8'.
  5. StoneFaced

    StoneFaced LawnSite Member
    Messages: 201

    If it were my design, I wouldn't want to see the concrete blocks against the brick, so I'd probably reset the tub when I was ready to do the brick work, so the brick flows nicely around the tub & doesn't look like an after thought. Otherwise, I would over extend the base now, so the integrity of the edges aren't compromised when doing the final excavation. You could also border the outer edge w/ the brick material to be used, but it could throw the pattern if not laid out carefully, pending the desired effect.

    Otherwise, I would probably just do a temporary base & reset everything when I was ready to set the entire patio base...as opposed to trying to match things up later. The finished product will be worth the extra effort in the end, as opposed to doing a mix and match. Just my 2 cents...
  6. Isobel

    Isobel LawnSite Senior Member
    Messages: 548

    I would just put down a concrete pad under the hot tub--the last thing you want to worry about is having the base settle or tilt a bit after the tub has gone in and is full of water.
  7. Bru75

    Bru75 LawnSite Senior Member
    Messages: 582

    My thoughts exactly.
    An 8' by 8' slab won't cost that much and will be more stable.
  8. Stillwater

    Stillwater LawnSite Platinum Member
    Messages: 4,889

    My spa was delivered and installed before my hardscape was finished. I prepped the spa base per spec of the finished hardscape grade. I used a six inch base of crusher run (crushed bluestone with fines) compacted it every 2 inches and made it dead level. so when it was time for the finish stone to be cut in I had everything to spec accounting for the 1 inch of sand base. (spa is not on a sand base it is on the crusher run) I would forgo the use of blocking it is not necessary but your call. What ever you do when installing a spa make sure it is dead level or you will notice it in the water line of the spa with the covers off. So any pitching in the hardscape should be done around the spa don't include pitch in the spa base or it will be seen in water line.

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