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Thread: My concrete decking may be sinking

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    My concrete decking may be sinking

    I have a 32000 gallon vinyl liner in-ground pool with a free-form shape. Since I have owned the house/pool, I have noticed that the decking around the pool no longer lines up with the pavers that line the decking. I believe some hollows are forming under the decking and causing it to sink along the edges. Has anyone else experienced this and had a successful fix? I can post pictures if anyone thinks it will help diagnose. Thanks in advance, this forum has always solved my problems.

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    frustratedpoolmom's Avatar
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    Re: My concrete decking may be sinking

    We love pics. Please do share....
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
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    Re: My concrete decking may be sinking

    Here are some pics. As you can see, in some places the decking is higher than the pavers, in others, the pavers are higher than the decking. I do have a high water table and when it rains heavy, the liner bulges in spots. I imagine this is causing some erosion. I guess my plan is to pull up the pavers, pack in some dirt/gravel until it levels and replace the pavers. Any other suggestions are welcome. Thanks.
    Attached Images Attached Images

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    dayhiker's Avatar
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    Re: My concrete decking may be sinking

    That's not necessarily erosion. It's probalby just settlement. Residential contractors do a horrible job compacting soil. I know our pool guy said he liked to wait a month before pouring the slab to let it "settle out." Depending on your soil type it can take much longer for soils to naturally consolidate.

    What part of the country are you located in?

    edit, uhhh, I'll guess you're in NJ.

    I haven't done a project there, but don't recall expansive clay issues in surrounding states. The only thing that made me question expansive clay is you said sometimes your pavers are higher.

    Do the pavers seem to move up and down over time and with rain events?
    The avatar is Spalding from Caddyshack
    18x36 vinyl IG - approximately 24000 gal
    Jandy SHPM1.5 Pump (1.5 HP); Jandy APURE 1400 SWG; Polaris PB4-60Q Booster Pump; Jandy CL340 Cartridge Filter
    (3) 4'x12' Aquatherm solar panels
    Next project, pump sound enclosure and lots of pool landscaping [6tons of stone 8) funnnn]

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    Re: My concrete decking may be sinking

    Sorry I have not been on in a while. But to answer your questions, the soil does have a lot of clay. I am not sure what shifts when it rains but I imagine everything does. After looking at it today, I think I need to pull up a bunch of pavers and re-level but in places, it seems like the concrete slab has sunken. Is there any way to re-level the slab?

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    dayhiker's Avatar
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    Re: My concrete decking may be sinking

    There's clay, and then there's expansive clay. They behave differently.

    Is there any cracking in the concrete?

    How long has the pool been in place?
    The avatar is Spalding from Caddyshack
    18x36 vinyl IG - approximately 24000 gal
    Jandy SHPM1.5 Pump (1.5 HP); Jandy APURE 1400 SWG; Polaris PB4-60Q Booster Pump; Jandy CL340 Cartridge Filter
    (3) 4'x12' Aquatherm solar panels
    Next project, pump sound enclosure and lots of pool landscaping [6tons of stone 8) funnnn]

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    Re: My concrete decking may be sinking

    It does not look like your deck is moving - it is interlock. Looks like concrete is still perfectly lined with the pool. Just take stones out, put some gravel to line it up with the deck and place blocks back.

    The reason is: Depending on your location, before poring concrete deck (assuming they have done it properly), contractors usually put concrete supporting columns under it (2-3 feet down). I know because I just noticed that soil under my deck is gone and it is just "hanging" so I called contractors to fill the gap under the deck before it will sink. 4 out of 5 contractors said that it is not soil/gravel which should hold the deck but those concrete columns and I should not worry.

    Igor.
    16K gallons Vinyl Inground with spill-over spa. 1.5 hp Pentair UltraFlow, 26" Pentair Meteor sand filter, Raypak Gas heater.

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    Re: My concrete decking may be sinking

    To clarify: interlock is canadian for pavers

    I see you are in NJ meaning temperatures do go below freezing. This explains why some pavers are higher - freezing water expands moving pavers all around. I had my fence raise last year because foundation was not deep enough and water was getting under, freezing and moving posts up.

    Igor.
    16K gallons Vinyl Inground with spill-over spa. 1.5 hp Pentair UltraFlow, 26" Pentair Meteor sand filter, Raypak Gas heater.

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    Re: My concrete decking may be sinking

    To answer the OP question, yes it is possible to raise sunken concrete deck sections-it's called "mud jacking." From what I understand, the contractor drills holes in the concrete and forces concrete with high pressure through the hole and under the sections, which raises the section. I have 3 sections that have sunk towards my coping that we are going to have fixed after we have our pool re-plastered.

    Having said that, it looks, to me anyways, that the pavers have heaved, not the decking on your pool.

    I will be sure to take before/after pix to show you all when the work is done. Our plaster job is scheduled for this Saturday--hooray!
    TF-100 Test Kit, 28,000 gallon IG , 3M quartz plaster '09, 48 sq ft DE filter, Heat Siphon SX5HP heat pump '09, Polaris 360 '10, Protect-A-Child safety fence

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