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Hot tub on flagstone

Discussion in 'Hardscaping' started by SUMMERSET, Nov 17, 2006.


    SUMMERSET LawnSite Member
    Messages: 6

    I have a customer who wants a flagstone patio. This is not a problem. She does not care if it is dry laid or laid on concrete pad in mortar. The only thing is that she wants to maybe put a hot tub on it in the future. My question is:

    What is the best method of laying patio if a hot tub will be installed later?

    Would the dry laid method be better to let the water drain off better?

    Would poured concrete be better to hold the weight of the hottub?

    Will sitting the hottub on top of the flagstone be a problem if they decide to put one on it?

    My gut feeling is that the concrete with the stone mortared in place at the correct slope (so water will drain off) is the way to go.
  2. Total.Lawn.Care

    Total.Lawn.Care LawnSite Senior Member
    Messages: 840

    I do not know the RIGHT answer to this, but I feel that the concrete slab with stone mortared in place is the way to go as well. Good Luck
  3. Sunscaper

    Sunscaper LawnSite Senior Member
    Messages: 305

    Wet for sure. Remember that flagstone needs about 1/2 pitch per foot to drain water off though being that it's so random. Otherwise you will always have some puddles. Problem being the hottub will be perfectly level and may show the slope being it will need to be to steep to shed water properly. Also you may want to consider pouring concrete first, setting the tub, then setting your stone around the tub.
  4. Edgewater

    Edgewater LawnSite Senior Member
    Messages: 457

    Most tubs need a very smooth surface to avoid stress points due to the weight. The stone used should be a near perfect as possible.
  5. Team-Green L&L

    Team-Green L&L LawnSite Bronze Member
    Messages: 1,775

    Flagstone is a pretty dense product that will hold the weight of a hottub as long as you use a good amount of aggregate and do a soil test of the sub-base. If it is clay you will need even more aggregate. I would suggest 6-8" of aggregate on this project with a geotextile layer to prevent settling. Compact the base in 1" lifts to insure proper compaction and do a compaction test if possible. You want 95-98% compaction. If you do these things you can land a 747 on the thing and guarantee it for 5 years comfortably.
  6. Uranus

    Uranus LawnSite Bronze Member
    from Mass
    Messages: 1,624

    I just build a new deck for my new hot tub. I stepped the new deck down from the existing deck and pitched it the same as the old deck. Well as soon as I filled the tub it was obvious that water is self leveling and the deck was pitched. On the low side the water is up to the headrests and on the high side if you don't have 2 people in it the top jets splash all over on high. Wherever you put the tub needs to be level. I think you should call a hot tub dealer and ask them. You don't want to have the base give under the weight (mine is 800 gallons) and compromise the tubs shell.
  7. RockSet N' Grade

    RockSet N' Grade LawnSite Silver Member
    Messages: 2,454

    There are all sorts of options available for doing a hot tub on slabs. I would prefer to pour a concrete pad under the hot tub area insuring a flat, level and stable surface. What you do to the ground underneath that slab to get compaction is up to you. After the pad, wet or dry set your decking material around the hot tub. Consider a couple drains in the equation so as not to have to slope your stone setting area as much and to help drain the area if you dry set.
  8. Team-Green L&L

    Team-Green L&L LawnSite Bronze Member
    Messages: 1,775

    We've been installing pads for hot tobs for 2 years now and haven't had an issue yet. The pitch is an issue and should not exceed 1" per 10ft. It will not give the best runoff, but no worst than concrete. A catch basin is recommended to help with drainage. We just finished the ICPI certification course which approves 6" of base for vehicular traffic and 8" for airport traffic.

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