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My house has a concrete patio (about 16x16 though its 5-sided) which is not sloped properly for drainage. In some sections it seems basically level, in others (near the doorway of course) it actually pools water.

The worst area I estimate slopes about 1/8" per foot the wrong way. I mapped it out by making puddles; this area is about 6-8' across, sort of an oval. It, and the door, are in one corner of the patio. From the door to the yard is about 16'.

The concrete itself is in excellent condition. It doesn't show any signs of settling nor is it cracked, I think it was just not poured with correct slope in the first place.

I am planning to deck this over with sleepers laid over the concrete. So the concrete appearance is not very important.

Ideas how to deal with the slope:

  1. (CAN'T DO) Pour some leveling compound - height by the doorway is already very tight, can't afford to lose any of it

  2. (POSSIBLE) Grind channels to achieve at least 1/8" per 1' slope, from the low spots to the yard. Rent a grinder like the example pasted below. Concern: might have to grind off a lot of material, maybe this is not practical.

  3. (POSSIBLE) Cut channels with a diamond demo-type saw with correct slope. Cut as many as needed. Concern: thin channels may clog with time.

Are either #s 2 or 3 feasible? Am I missing anything important, or is there another option I'm ignorant of?

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We did end up renting a walk-behind grinder and it did the job.

It was not "easy" but only took a few hours, and the rental cost was reasonable. The ideal grinder we wanted was out of stock but would have had a smaller cutting width. However the one we used despite being larger still didn't take excessively long to do the job.

We had a small amount of water running the entire time which basically eliminated airborne dust, removed the dust, and indicated when the drainage was working well enough. We used that the judge when it was "done" rather than focusing on any exact measurement of slope.

In hindsight I think the job seemed intimidating but it was actually quite reasonable to do.

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Grinding or cutting channels would be really hard. Some spots they's have to be up to an inch deep. I would drill a few 1/2" holes in the concrete where the water pools and let it just soak into the ground. You could cover the holes with a drain cover if you were concerned about the appearance.

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  • I like this thought... I don't know what's under the slab. Probably gravel and then our normal clay soil. I wonder how well that would soak away? Aug 16 '20 at 16:34
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    @UuDdLrLrSs Probably the same as at the edge of the slab... you could experiment.
    – JACK
    Aug 16 '20 at 16:48
  • With sleepers and decking appearance won’t be an issue, I find drilling multiple 1/2” holes may take as long and still have issues plugging. surface grinding 8’ in a couple of places could be done with an angle grinder and cutting disk less expensive than renting that grinder for 1/2 day but by hand would take a little longer. I like to direct water away from the home even if no basement.
    – Ed Beal
    Aug 16 '20 at 19:22

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