"Basement floods at the outside stairs"
Column #846 05/14/2011
On The Level
Q. We have a two-story house with a basement. The house is 35 years old. The problem is that when we get heavy rain the outside cellar drain, located at the bottom of the stairwell by the basement door, floods. Water then collects and once it reaches the bottom of the basement door, a up about 3 inches from the floor, water begins to seep inside causing the basement to flood. I called a company that says it specializes in drain problems. The person they sent out to look at the drain told me that when my house was built outdoor drains essentially emptied into a series of gravel filled tunnels under the house. He said that since there was no drain pipe, there wasn't any sort of structure he could clean. He said that over time silt collects and the drain stops working. He also said that there was little if anything I could do since any type of work would require cracking the concrete stairwell and the basement foundation to run a new drain, which would be extremely expensive. He suggested covering the outside stairwell with a tarp. I think that water also seeps from the surrounding ground into the stairwell so I doubt that covering the area would solve the problem. I also find it hard to believe that there is nothing short of ripping up the foundation that I can do to prevent my basement from flooding each heavy rain. I've purchased a portable sump pump, but if I'm not home when it rains, then I'm out of luck. What options do I have? I'd certainly appreciate any advice you may have.
A. I don’t believe the fellow who came out and looked at your areaway, that’s what that basement exterior stairs and entry are called, wanted to get his hands dirty. He was correct in telling you that the drain there is silted shut and that’s part of the problem. He probably wasn’t around when your house was built or if he was he wasn’t in the business of installing areaway drains at the time. I was so I can tell you how it was done.
After the foundation walls were run up and before the basement concrete floor slab was poured, a perimeter trench was dug inside of the foundation walls all around the basement that ended in a sump pit. The drain pipe itself was normally perforated flexible plastic pipe--three or four inches in diameter--placed in a bed of gravel. Then gravel was spread over the earth of the basement floor to a thickness optimally three to four inches deep, then a sheet of thick plastic vapor barrier was placed over the stone and the floor slab was poured. The areaway had a bell-trap drain installed which connected with a two inch plastic (solid) pipe that dumped into the perforated pipe just about a foot and a half inside of the door under the slab. Bell-trap drains are used because they have a small perimeter trap that ostensibly intercepts silt before it gets into the drain pipe and clogs it but we both know it doesn’t take much to clog that drain.
What the contractor described as the drainage system that he thought was there was a variation of the French drain theme that was sometimes used-- unsuccessfully in the long run-- before the system I described was set in place through the building code. Overall building codes in the County around here were placed in the law in 1966 and were slowly followed but by the time your house was built they were up, running and enforced.
It could be that the silt that has clogged your areaway drain pipe over the last 35 years is as hard as a rock and will not yield to snaking or flushing with a high-pressure hose--but I’d try that first. That’s where getting dirty comes in. If that fails then he was right to a degree about breaking up concrete. You’d need to cut a channel from the areaway drain into the basement inside the door to locate that perimeter drain and install a new drain line. It’s not wholesale demolition and you could do it yourself with a rented roto-hammer that will make breaking concrete relatively easy. If you decide you want to hire someone to do that get at least three estimates and tell them exactly what you want done so your bank account won’t get sent the cleaners.
I see areaways covered with both permanent or makeshift covers that tell me right away the drain is clogged. Controlling the other water sources getting into the areaway stairs should be controllable starting with the gutters directly over head to the grade on the outside of the areaway wall itself. I have seen folks so frustrated that they have dug and installed a dedicated sump pit and pump at the base of the areaway steps. Extreme but it works.
When you finally get the drain clear set a water permeable door entry mat over the drain so the it intercepts debris before it gets to the drain and won’t let only a handful of leaves to clog up the works. When you get the drain working you can run a hose into it and go look in the sump pit and watch for water draining into it. In some instances the water will enter the perforated perimeter drain and percolate into the ground long before it even gets to the sump--it varies from house to house.
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