I want to raise my hot tub to the level of my deck. My deck is 50" high and my hot tub is 29" inches high and is a smaller 4/5 person tub. I have a concrete slab in place from an old hot tub. I was thinking to add two layers of cinder blocks and then a layer of thick pavers to reach the height. My slab is a bit uneven (about 1 to 1.5 inches) so was thinking to put some gravel down first.

In the end it would be 1) concrete slab 2) gravel layer to level 3) two layers of cinder blocks 4) one layer of thick pavers 5) treated plywood to ensure levelness 6) hot tub, which would then be level with the deck.

Is this a bad idea in your opinion or would it provide sufficient support? I'm wondering specifically if having so many layers would cause any instability at that height or if it's low enough to be ok.

Thanks for your input!

  • 1
    Not sure about everything being set on a layer of gravel... Would you consider pouring a section of concrete about 2" thick to get a level starting surface? (other suggestions welcome - I just don't like the gravel)
    – JPhi1618
    Nov 8 '19 at 21:41
  • @JPhi1618 yeah thought of that. I was hoping to avoid pouring new concrete if possible in order to get it done ASAP if this solution is workable.
    – loady toad
    Nov 8 '19 at 22:04
  • Does the hot tub manufacturer recommend it be installed on plywood?
    – Lee Sam
    Nov 8 '19 at 22:10
  • 1
    There is about 21” difference in height plus slope discrepancy. Will the “cinder blocks” be mortared into place AND have vertical and horizontal reinforcing? This still leaves about 5” height difference, which I assume will include the “thick pavers” and plywood you mentioned. With so many layers, you’ll need to insure each is solid and all anchored together. Are the pavers mortared into place or “dry set”?
    – Lee Sam
    Nov 8 '19 at 22:17
  • Could you build a wood deck to support the tub? Using posts of sufficient size and spacing? Almost 3' of cinder block and pavers...not sure I'd trust it myself.
    – Jeff Cates
    Apr 8 '20 at 6:24

I have used cinderblocks up to 3 layers high on a large tub 9x9. I would put the blocks directly on the slab then fill them with gravel. The cinderblocks are not known to be strong unless filled but if they are filled even a large tub held up for almost 20 years.

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