Drainage

Here's a project that got out of control. The whole concrete slab in front of the door sank backwards, so rain puddles in front of the door and seeps under the frame into the living room, where it destroys the shopping bag floor cover.

I pondered this issue and decided the best thing would be to destroy the whole slab and re-pour it with a slop toward the lawn and not the door. But that sounded like a big project that could force me into other problems. So Plan B was to cut a channel and dig down and put a french drain and then drill some holes or use lattice pavers so water could drain down to the french drain. But that involved digging a trench a foot below a channel in concrete...

Plan C came when I discovered PVC micro-channel drain for sidewalks or in front of garages. Hey, this might work. So, I cut the channel with a freakin' circular saw and masonry blade, which was tool abuse, but it worked to cut a 3 inch deep slice. Unfortunately, I needed a 5 inch deep cut, so I had more work drilling and hammering the channel open.

 

The weird thing is that when I had only the thin cuts in the concrete we had a rain storm and all the water drained down the thin channels. There was no pond in front of the door. Everything was dry on the other side of the cuts. I think the cuts were enough to solve the draining issue since water always had a lower way out to the lawn. But I was not convinced it would work for a huge rain so I broke out the channel and agonized over getting the channel drain to angle slightly toward the lawn. This was agony because the slab had was pitched badly the opposite direction. So, this created a big lip/drop down when I had the drain slopping toward the lawn. It's a tripping hazard, but I had no choice and envisioned a grate over the drain...or a door mat.

I suspected that when I finally started to cement this in place my errors would become clear and that's what happened. As soon as I had committed to mixing cement I started to visualize what was happening with the water. I was thinking correctly, that I want a sloped drain toward the lawn like a roof gutter, but this is not totally a good comparison. A roof gutter is not water-proof and will leak at seams with standing water. Only a slope minimizes the leaks and maximizes drainage. But a ground level channel drain is UNDERGROUND, so who cares if it leaks? Furthermore, the channel drain is 3-1/4'' deep. So, if the channel drain was dead level, or even sloped in the wrong direction then it will STILL DRAIN as long as the yard end of the drain is not over 3-1/4'' above the grade of the opposite end of the drain. See? The drain would have to fill completely with water, with 3-1/4'' of water for the pond to return. But if the drain was dead level with the slopping slab, even slopping in the opposite direction of the lawn, it will simply fill up with water to the level required to start draining toward the lawn, which was probably 2'' of water, which is still below the top of the channel drain, so I would never see ponding. The water will be captured in the drain until it starts to drain. So, I don't think I needed to agonize about the slope of the drain since standing water inside the drain is not a big deal. It will evaporate in the heat of the sun. But I did agonize over the drain slope as I tried to ensure complete drainage, and thus caused there to be a depression where the slab and the drain do not match.



I think my instincts to get the drain to slope in such a way that there will be no standing water was correct, but I wanted to show how this was not the only way to skin the cat. The difference in slopes between the slab and dead level and a drain slope caused the offset depression that becomes a tripping hazard and another problem to fix.
Again, the solution is to tear all the concrete out and compact the area and slope the new pour in the direction of the lawn, but I have none of that equipment and am trying to solve these problems with what I can assemble myself. I can't justify a $1000 solution to the drainage problem, but I can justify a $40 solution that creates a tiny depression that can be covered with pea gravel or a door mat or a metal grate or something that eliminates the depression but still allows water to reach the drain.

The lesson here is to simplify everything. I do believe sloped cuts in the slab would've solved the problem with minimal effort. Water would've drained down the cuts into the lawn and there would've been no tripping hazard. Hell, make 3 cuts. As long as lawn end of the cut is below the opposite end then water will drain down the cut. The slab remains mostly unchanged. The only cost is the masonry blade. Maybe the cut channel fills with debris and stops draining but that could be solved by making it wider so it can be swept clean.


This solution will work, but it was a little complicated and I'm trying to keep things simple since the house is neglected in general so that any little project can quickly become big if I dig too deep into the problem. Pouring a new slab might be a solution but consider what insanity that would involve as soon as I exposed the area beneath the wall. It leads on and on and the project balloons out of control. I'm not trying to reinvent the wheel but I do want to make some attempt to solve major issues like water entering the front door. It's a fine line between doing nothing, doing something that almost works, and doing something that works but creates other problems and creates.
Here's a mathematical graph to represent this.