Slab of concrete under lawn!

littlebum2002May 13, 2014

When I bought my house, there was an old shed in the backyard that I had torn down by a "professional". When the job was almost done, there was one slab of concrete left, and my dumpster had filled up for the upteenth time, so instead of paying to rent a new dumpster just for the last slab, we decided to cover it with dirt and let the grass grow on it. (I was poor and an idiot, I realize that now)

Today, as you probably expect, I can tell within an inch exactly where that slab is under my lawn. Every summer the grass on top dies and only weeds grow. The slab is about 10' x 10', and has about 6" of dirt on top.

I've never actually sodded my yard, over the years I've just added St. Aug runners and vigilantly weed & feed and I've got it to about 50% St. Aug and 50% weeds/bermuda/other junk.

WHY isn't grass growing here? It doesn't make sense, to me, that a cement slab under 6" of dirt would affect my grass, but it does. Is it drainage issues? Not getting nutrition? Something else?

Now, I would have assumed that 6" of dirt is enough for St Aug to grow on top of cement, but apparently it isn't. However, my theory is that I simply haven't tried hard enough. SO my first option is to till up this area, put down about an inch of good black dirt, then sod it with a good carpet of St. Aug and give it a chance to really take off and grow. Shouldn't that work?

My second option is to get some other sort of grass that may be more tolerant of this less than ideal condition and plant it instead. This is not my favorite option since I'd much rather a uniform lawn.

My third option is to maybe get my hammer drill and drill holes in this cement to drain water or something? This will take forever though since that slab is THICK and that hammer drill turns your arms into jello.

My last option is to finish the job. Get a 'dozer out there, dig up the slab, and get it disposed of. This is the best option of course, but it will be hard and expensive.

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forsheems(Lexington, NC)

The grass dies each summer because the 6" layer of dirt on top of the concrete slab can't hold enough water to keep the grass alive. I've seen the same situation with septic tanks that weren't burried deep enough. All is well until the heat of summer hits. About your only option is to dig it up and remove the concrete.

    Bookmark   May 13, 2014 at 4:40PM
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beckyinrichmond

Perhaps you could do something other than lawn here. You could install a patio or deck or water feature. You could have mulch and potted plants. You could install playground equipment or a big rock. Or another shed. Or a gazebo.

    Bookmark   May 14, 2014 at 6:37AM
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littlebum2002

Well, yesterday I went out and tilled up the dead grass as much as I could, put a couple inches of topsoil on top with some grass starter fertilizer mixed in, and then put some good St Aug grass sod. Hopefully there's enough room now between the grass and the slab to retain water.

If not, I don't think I'm going to tear up my yard with a bobcat digging around pulling this thing up. I think I'll go with the other suggestion, and maybe put a raised garden there.

    Bookmark   May 14, 2014 at 12:57PM
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toronado3800 Zone 6 StLouis(6)

A great idea. In my zone I ztruggle to keep the weeds out of my cactus and yucca area. If it were over a slab of concrete that may benefit the low moisture loving plants.

No warranties but an interesting experiment.

    Bookmark   May 14, 2014 at 1:14PM
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kudzu9(Zone 8a - PNW)

I'd go for the easiest fix involving the least work and be done with it.: rent a jackhammer for a day, start at an edge, and get rid of it. You can pile up the chunks and dispose of them over time, or put an ad online or in the paper for someone who is looking for solid fill who will cart them away for free. All of the workarounds you describe sound like a lot of trouble to half-fix a problem. Do what you know has to be done, and then you'll have total flexibility with your yard.

    Bookmark   May 14, 2014 at 1:23PM
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neilaz(9a)

Tiling wasn't a good idea (it will settle uneven) but that is done. Since the problem is that area doesn't hold as much water(roots not as deep) just give that area water more often. A little hand water to supplement.

    Bookmark   May 14, 2014 at 4:19PM
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littlebum2002

That's my idea. I just wanted to give it a good head start with some healthy sod on top of black dirt and fertlilzer. Now I'll just water the heck out of it and see how it survives.

I didn't REALLY till it, not with a tiller at least. I ripped up all the dead grass and raked up the dirt underneath to soften it up a bit to help the roots grow through.

    Bookmark   May 15, 2014 at 9:56AM
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lazy_gardens

Well, yesterday I went out and tilled up the dead grass as much as I could, put a couple inches of topsoil on top with some grass starter fertilizer mixed in, and then put some good St Aug grass sod. Hopefully there's enough room now between the grass and the slab to retain water.

There is very little you can do on top of that slab of concrete that will compensate for it being there. St Augustine grass quickly establishes 15-24 inch deep roots, depending on cultivar, and you have given it less than 1/2 of that.

How thick is the slab? If you use a concrete saw and slice it into squares or small rectangles as deep as you can, whacking it out with a jackhammer is easier because you have introduced natural cracking points. Make two cuts, about an inch apart, and use the jackhammer at that point.

And you can usually get someone to come get and recycle the chunks as "urbanite".

    Bookmark   May 15, 2014 at 10:42AM
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littlebum2002

I don't really remember how thick it was, but it was under a shed, and I remember it being on the thick side, so I'd guess at about 6" thick.

The cost of having someone come pull it up and dispose of it isn't really the issue. I mean, cost is always an issue, but a bigger issue is having a 10' x 10', 6" hole in my yard wile it's being torn up, then having to fill it with dirt, then growing grass from scratch, etc. Considering that, I'd rather have someone tear it up than cut it up myself, because that's just going to take me forever and I'll have a huge hole in my yard the entire time.

I think my top choice is going to be a raised garden, but considering it's kinda in an awkward area of my ward for one, I might still consider getting it torn up. But I've always wanted a nice vegetable garden, and if I raise the garden 4-6" over the grass, that will give it close to a foot of root room which I can only hope is enough.

    Bookmark   May 16, 2014 at 11:15AM
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forsheems(Lexington, NC)

You could call around to a few of the local guys that do grading. Someone with a larger skid steer could easily dig out the pad, bust it up, and haul it away in an hour or less. They would probably be able to haul in enough dirt to fill the hole and level it out at the same time.

With that slab in place it's always going to be a dry spot.

    Bookmark   May 16, 2014 at 11:55AM
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