You need a subsoiler attachment on a tractor. Basically a one point plow. You drop it in on the edge of the concrete and drive away as far as you can. It will cut a grove in the dirt below the grass line and allow the water to drain away naturally. It does have limitations, it will not work if you are running up hill. But if you have flat to a slope falling away it will surprise you how well it works. Just my opinion.
So, an 'overlay' slab is such a thing? Is this a DIY project or must one have a pro? I am not familiar. On top of this thread's 'problem,' just downstream of the slightly lower area in the finished slab, is my concrete driveway that connects to the finished slab, also 61 years old. Nearby pine tree roots (my dad should have never let them grow close to the driveway) have cracked the driveway and made really rough from the 'undulations.' Even some broken sections. I always wondered if you could fix that with an overlay. My dad and a worker did overlay it with more concrete many years ago but neither knew much about concrete and it didn't work well. I figured to fix that driveway, I'd have to just start over. And it would cost a small fortune. (It's a pretty big area that is in need of repair... 100 ft long.) It's still functional, just looks bad, is dangerous to walk on (stub your toe) and it retains water after a big rain. That burcam pump is a solution for just pumping it out, yep... down to 1/8 inch. I do now see another option that would not involve pumping and if it worked, it would automatically drain all but the lowest part of the spot in sink. I could get a diamond wheel and cut a groove out sideways to the lawn and then dig a trench down the side of the driveway; the driveway and yard slopes down from there. Good advice in here.
An overlay could work, if done properly, using quality materials...at least for a period of time. But its my opinion that an overlay will always fail at some point in the future, which may be longer for you since you are in the south...up here in the north, the freeze/thaw cycle would pop that loose in no time.
You could also just drill a few holes for drainage with a concrete bit in the lowest areas where the water is deepest. 3/8" or 1/2". Let it drain into the ground underneath the slab.
That's another good idea! I have some badass clay in some spots, hope it's not that. Drilling such holes, how far apart would you do them?
I wouldnt bother drilling holes. That only works if the pad is laid on crushed stone. Even a sand base will clog rather quickly. It works for temporary draining on job sites but long term,,,,nah. Louisiana? Not much real sand there, more of a silt with a washed topping. Best bet is to build it back up. Perhaps even a raised pad inside the shed and surrounding areas if possible. Pictures would help. If a pad is out of the question there are premixes designed to build up concrete areas. Read the directions and specs carefully as thickness varies greatly. May even need to use two different products. One for the deeper areas and another to feather out the edges. JMO but if you go the thin leveling method buy the product from a real mason supply company. The stuff from box stores just doesn’t compare,,,even the same product. Somehow the box stores get batches made up that really suck at workability.
