Slablifting / slabjacking / mudjacking questions
Hello,
I am going to lift a concrete patio slab that has a negative slope towards the house!, maybe at about -2 degrees. this is creating a big drainage problem.
Generally, there are two options for slab-jacking
1. a grouting method, where cementicious material is pumped under the concrete. weight -> 100-150 per cubic foot
2. a polyurethane method of injection that cures when it expands. that weighs far less -> 4-8 pounds per cubic foot.
weight is a concern because of resettling.
My concern is, for either method, is there any concern of “tainting” the soil?, especially with polyurethane? I planed on extending my vegetable garden only 2 feet away from the slab.
Does anyone know if any chemicals leech into the soil, to the point where I should be concerned for either method?
thanks
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Replies
Gramps,
You wrote that your slab slopes toward your foundation, "creating a big drainage problem." The reason for that problem is that the slab effectively interrupts the rain and directs it toward the direction of the slab's slope.
That's good news for your garden soil. Since the concrete slab interrupts the rain, there isn't likely to be any rainwater leaching the materials under your slab. If you have a very high water table, with flooding that rises to the level of your slab, leaching is certainly possible. But in that case, your vegetable garden is in the wrong place.
I think the previous answer is answering the wrong question. this question is not where the vegetable garden should be, but is either slab lifting method bad for the soil surrounding it. What I need is knowledge about slab-lifting practices itself. Are any of them environmentally unfriendly?
the slab slope is the issue, the main reason for concern. it has to be changed or foundation problems will occur.
To change the slope, a grout material made of a cement mixture or polurethane has to be pumped under the slab. the slab has cracks in it, like all do, so any water that reaches the cracks will drop down below where the new support is (polurethane or grout).
since the new slope has to be away from the house, the pumped material sits beside the flower bed. I don't know how much it really matters what side it is on.
The garden location issue is only second in importantce, but I would like to have one in that location.
This is a common problem which is often caused by settlement of the house foundation trench backfill. We usually resolve it by taking up the slab, regrading and repaving. The greenest way to do this is to re-use the broken pieces of slab as irregular sand-set patio paving: in the right hands the results can be stunning.