Home groundwater drainage details count big
Properly service your home drainage systems for best results. I received a phone call yesterday from a couple for whom I had constructed hand excavated french drains about 2 years ago. They are very nice people. The wife was highly suspect of the validity and usefullness of hand excavated french drains to solve their home drainage problem at the time of construction.
The home was getting groundwater in the basement. There was a negative grade at the foundation. Uncovered window wells filled with rock. Poor gutter installation and an old rain drain discharge pipe that poured into a concrete patio, plus loose soil on the exterior foundation wall where the homeowners planted tomatoes.
The conversation with the wife yesterday started with the statement that they had received no groundwater into the basement since the hand excavated french drains were installed two years ago. They were very pleased with the work. Recently however, they had groundwater coming in where the wall meets the floor in the basement.
My initial response was that something must have changed recently to produce that condition, given we have not had much rain so far this fall. Given that last winter we probably had 20 inches of rain or more, and they had no leaks.
So, I told her that I would come by the home this morning and look it over. She thanked me for calling back promptly.
During the original construction, the hand excavated french drain was constructed away from the foundation wall, the grade was increased away from the foundation wall to run water away from the foundation, and a solid 3″ abs rain drain discharge pipe was laid in the bottom of the hand excavated french drain along with the 3″ perforated pipe, to plumb the gutter downspouts into the hand excavated drywell. In addition they have two window wells on that side of the home. The hand excavated french drain in located on the gable roof end of the home where there are no overhangs or soffetts to protect the area from rainwater. These are always problem areas. The window wells are concrete and very low to the ground. The large size of these window wells eliminates the addition of any pre-made metal high side window wells which if installed would allow the dirt level to be raised along the foundation wall creating an even better compacted grade away from the foundation.At the time of construction I had advised the homeowners to cover the window wells with a sloped shed kind of cover where the rainwater was pouring in. Water was making lines down the interior basement walls directly under the window wells as evidence of this rainwater entry to the basement.
This would shed the water off the window well cavern and slope it to the exposed rock hand excavated french drain where it would run to the drywell instead of the basement.
Upon investigation today, the window wells were no longer covered and it was raining right in them. The wife said that approximately 1″ of water was observed by the husband, standing in one of the window wells near a fallen downspout. The downspout had never been placed into the 3″ rain drain abs rain drain discharge pipe that was constructed for it, and in addition had broken from the old placement. The roofwater was pouring out next to the foundation. The area that was graded away from the foundation between the window wells, with the addition of dirt against the foundation wall, had been dug up in two places for tomatoe plants, not surprisingly directly outside the area in the basement where the leaks were discovered as well.
So, window wells holding water, downspout water pouring next to the foundation, flattened grade because of the digging for plants, and loose soil next to the foundation in the previously compacted area. Last year no water, this year a lesser problem, but never the less a problem.
After discussing these issues with the wife, she saw my logic, and started taking notes, as she usually does. The husband didn’t seem to think a combination of those drainage issues would matter. He later came around a bit too, and mentioned a city of moles that had always enhabited the foundation wall. Tunnels everywhere. The conversation ended quite cordial in nature, and they indicated their understanding of my point of view.The husbands original statement after I explained the issues that were changed since the construction was, to paraphrase, “he was not surprized and understood I probably would say that”. I assured him that if I thought the work was a contributing factor to the problem, that I could and would replace it and correct it at my expense. He had not been feeling well I am told. All in all it was a learning experience for all of us. He started to mello out when I went over the logic a few times.
The moral of the story is, stay with the details that are suggested to you by your drainage contractor. The drainage contractor sees these types of home drainage problems over and over. We know factors that create problems. The objective of the work is success. Do the details and keep gutters clean and straight without leaks. Do not flush gutter debris into the rain drain discharges. Don’t excavate and plant next to your foundation and expect the best groundwater removal to occur in loose soil.
Keep the exposed rock in hand excavated french drains clean and cover holes and entry points like window wells to shed the groundwater from the side of the foundation.