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Thread: Best material to use for fill under a patio block?

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    Best material to use for fill under a patio block?

    Hello all,

    I am new here, and I have done alot of searches and read many forum posts looking for my answer, but I did not find the answer to this question.... so here goes:

    My situation is that I am in the process of replacing an 18' above ground pool. On the upside, the area is already very level. On the downside original pool was not installed on patio blocks, so I need to install them. A deck abuts the pool on one side (deck spans a little over 2 pool rails).

    While attempting to install the pool block to be at ground level I have found that the ground on the deck side is very loose. The patio blocks I am installing are about 2" thick, and while digging down I noticed that the ground gets alot firmer at about a 4.5" depth (packed rock). Anyway, what I want to know is what can I use to pack beneath the patio block that will avoid it settling over time, (I should mention that the main pool area is very solid (apparently mechanically packed) *large* crushed stone, so lowering the entire grade of the pool would be very, very difficult).

    Originally, I tried dirt, but the dirt I have is either topsoil or very clay-like. Even after alot of hand tamping down (using a 6x6 post) the dirt mix seemed pretty "flexible". (I can't use a mechanical tamper because the patio block hole is only 16x8x2) and I would prefer not to compound the issue by making an even bigger hole.

    My second attempt was try layering the dirt mix with a layer of crushed stone ("Vista Red" which I purchased from Home Depot). Basically I put a 1" layer of the dirt mix (then tamped it down alot) then a layer of the crush stone and tamped/pounded into the dirt mix, then another layer of dirt, tamp, crushed stone, tamp, etc. This way seem to make a firmer sub-layer but is still not as rock-solid as I would hope. I am also concerned that using crushed stone (even pounded into a dirt mix) might cause problems down the line. (I have read gravel is not a good base, but I am not sure if this crushed stone/dirt mix is better or not?).

    Sorry for the long post, but I want to give some details regarding what I am working with.

    So I guess my question is: When you need to firm-up or re-build a patio block hole that is slightly deeper than desired, what is the best material to use? (Assuming hand tamping is the compression method).

    Thanks.
    18' x 54" ABG

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    Mod Squad Bama Rambler's Avatar
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    Re: Best material to use for fill under a patio block?

    What about stacking two pavers on top of each other? If that gets you to the solid base it may work out good. Even if it was a little low you'd only a little bit to build up.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
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    Re: Best material to use for fill under a patio block?

    Wow, amazing timing.... I just posted this to the correct forum and then tried to delete this post because i was not getting any replies... And now i have a reply!

    The two pavers wont work because the rock below is not even and the only way to make it even would be to remove a large rock and then i would have an even bigger hole.

    I would assume that this is a fairly common problem since digging any level hole often requires some amount of re-filling and with such a large amount of weight there must be a common way to refill/repack the hole so as to allow it to withstand the pressure.

    I thought about using broken block pieces or even larger stones ( like 1/2 fist sozed).... Heck, i imagine there are tons of ways to do it, but i really want to do it the right way, i just am not sure what the "right way" is.
    18' x 54" ABG

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    Re: Best material to use for fill under a patio block?

    Also two patio blocks stacked actually might be a tad too high (i was ballparkng the 4.5" estimate), but i think that still might actually be the better anyway. I guess i am asking: Is it okay to have the patio blocks higher than the rest of the pool if the all the patio blocks are still level with each other?

    Reason i ask is because a few of the other uprights are right over very rocky areas and it would be alot easier if i could place the blocks at half depth (1") rather than full 2" depth. This would allow me to have two blocks stacked (one and a half sunk) for the softer areas (to get down to the solid ground) and one block (half sunk) for the harder/rockier areas.
    18' x 54" ABG

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    Best material to use for fill under a patio block?

    I don't know if that will work
    I know on my pool the bottom rails kinda snap into the upright
    Did you have any issues with the old pool sinking?
    If not I would just leave it be
    18' x 33' Aqua leader AGP (~19k gal) w/hayward swimpro voyager cartridge filter and 2hp hayward pump.
    8 Gal LQ, hayward heater.

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    Samantha Sabrina's Avatar
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    Re: Best material to use for fill under a patio block?

    In your case why bother with a paver in that hole, get a bag of quickcrete pour it in the hole, add water and use a trowel to smooth and level.

    That will be very solid, fill the hole to proper height, easy, and inexpensive.
    Samantha

    In the process of building for a 22' Intex Ultra Frame, (completion date up in the air at this point).
    We could not beat our backyard into submission so we "Buried It".

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    Re: Best material to use for fill under a patio block?

    @HighlandRef - yeah the old pool was sinking (although only slightly) on that side. Also that is the side where people get in and out of the pool so moisture is an issue. Planning to divert water away from pool as well, but ground is soft which is why i went down a bit deeper.

    @Samantha - Quickcrete probably won't work because i had done something similar next to the pool where i had a hole due to skimmer overflow and a break in the liner. Patched it with quickcrete, but it shifted/heaved within a year (I'm in the northeast, so winters are an issue)... The heave created a gap for water between the pool and the concrete patch... i actually removed that concrete block and need to patch that hole as well, which i was going to use whatever fill was recommended for under the block. Btw, that hole is only very slightly under the wall, mostly outside the pool.

    Any other ideas? Anyone?
    18' x 54" ABG

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    Mod Squad Bama Rambler's Avatar
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    Re: Best material to use for fill under a patio block?

    I was going to suggest the quickcrete fill. The only difference is that I was going to suggest putting the paver on top of the quickcrete. Stone dust or crusher run is about the only other things I can think of.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    Samantha Sabrina's Avatar
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    Re: Best material to use for fill under a patio block?

    As bama said, around here we call it screenings, (same thing I am using for final level under our pool), it is not as fine as sand but not like pebble stone either. Once this stuff gets wet and dries it is like concrete, but it will wash out if not in a hole or surrounded by something, but it does make a great base.

    I will be posting new pictures of our build project later this evening, we have just leveled the shed area with this stuff, it was a major pain getting the 2x6 to scissor it off, ended up having to work a short distance then use a rake to help loosen another section.
    Samantha

    In the process of building for a 22' Intex Ultra Frame, (completion date up in the air at this point).
    We could not beat our backyard into submission so we "Buried It".

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    Re: Best material to use for fill under a patio block?

    At Home Depot/Lowes get some bags of leveling gravel and leveling sand. Another alternative is crushed concrete or crushed limestone. The latter is availiable via the truck load. Crushed concrete is what my builded used under the pavers for my decking.
    7,500 gal, IG pool, L shape 22' x 15', 1.5 hp pump, cartridge filter, AquaPlus SWG/Controller, Pebble-Tec liner.

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    Re: Best material to use for fill under a patio block?

    Thanks for all the suggestions...

    I also found another thread regarding the lime/cement idea here:
    soft-spots-in-clay-t18598.html

    I will see which of these various options I can get at my local HD.

    Thanks again to everyone for the great suggestions!
    18' x 54" ABG

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