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Stone foundations & French drains

Posted by solaris_2009 (My Page) on
Thu, Jan 1, 09 at 11:50

I've worked on many old houses, but need some advice on this problem. I'm currently renovation an 1810 cape in western Maine. Structurally, the house is in good shape considering its age, but there is a real water problem in the cellar. The walls are comprised of the usual split rock and some field stone, and they still straight and solid. It is a full cellar with approx 7' walls. Some time ago, a concrete floor was added with a French drain around the perimeter and a sump pump at the low side. The problem is the amount of water coming in from the outside - especially on the front of the house that faces toward a slight hill. When the pump was off last year (when the house was up for sale), the water rose to almost 3' deep. Even when the pump is running, moisture is a constant issue. The problem is compounded by the rain water shedding off the metal roof.

My question: Can I put a French drain of sorts on the outside of the house to divert the water away from the structure without damaging the integrity of the foundation? Or is there a better way to address this problem?

Many thanks in advance for your thoughts on this issue.

Follow-Up Postings:

RE: Stone foundations & French drains

You may need a lot more than a french drain. Get a couple of really reputable contractors in there to check what's going on because in a house that old with those walls, etc, the problem could be more serious than you can tell from what you're just looking at on any given day and may involve land issues.

RE: Stone foundations & French drains

That much water sounds like an underground stream, high ground water, or perched water on rock. You night need to dig up the outside of the foundation and install a footing drain and waterproofing although there is no guarantee that would completely solve the problem.

RE: Stone foundations & French drains

underground stream

When I hear "concrete floor was added" I recall a home I looked at one time where the contractors excavating the basement for greater height hit running water. By the time they could get sump pumps, the 30x50 foot basement was a six foot plus deep swimming pool. They installed two high capacity pumps running continuously.

On a new home, the owner insisted on a deep basement to give him minimum 10ft. clear ceilings. After the excavator hit running water, wells and pumps were installed at several points on the perimeter of the property line to alleviate the flow.

We often build above a world of water that doesn't like to be disturbed!

RE: Stone foundations & French drains

As noted above, you need to figure out what's causing the problem.

If the roof is shedding rain, start with gutters and downspouts to divert the water to the low side of the house. A french drain might work, but you'd need to know what the problem is--it wouldn't solve an underground spring, but could be sufficient if it's primarily rainwater coming down the hill towards the house.

Stormwater & French drains

I'm guessing a french drain is what I need, maybe not. The rear of our house is at the bottom of a steep slope of about 45 degrees. About 15 ft back from the house it levels out to a "platform" running the entire length of the house.
The platform is at least 15 ft wide and flat, then the land rises again. Water runs down the slope causing seepage into an unfinished basement with a dirt floor. I'm thinking trenching out at the forward edge of the "platform" would be a good place to put a french drain and have it descend to one side of the house where the sun hits the lawn. Any thoughts are appreciated.

RE: Stone foundations & French drains

It may work. In any case, it's a lot less risky than excavating a loose-laid foundation that was likely never meant to be freestanding.

RE: Stone foundations & French drains

Do you have any pictures? It would help if I could see the slope of the land.

It might be helpful to film the next heavy rain, so you can see the pattern of rainfall. Also stand in the cellar to see where it is coming in. Of course, if it is seepage, there won't be a clear cut entry point.

We had to dig down to the bottom of our foundation, have waterproofing done, and perimeter drains installed at our house, as well as a sump. My house is not antique, though, so we didn't have concerns about the foundation's stability.

Our front stoop was a culprit in our house, so I would also check the sills near the stoop.

I think this can be solved, but it can be frustrating, and the first thing you do may not be enough. The drain idea sounds good to me, and would likely help even if it's not the complete solution.

RE: Stone foundations & French drains

solaris: My own house is of the same vintage with the same sort of foundation. It would have been pretty much unheard of for builders in 1810 to design a cellar without a gravity drain to allow water to exit from the cellar's interior. After all, there were no sump pumps or electricity available and they were well aware that water would penetrate the foundation.

I would look carefully for some evidence of an entrance for such a drain on the downhill side of the foundation. It's possible that it was covered over when the cement floor was added, but this doesn't seem likely. More likely is that the drain has become clogged over time with silt, etc. It is sometimes possible to clear the drain, which was usually lined with rock, from the inside using a water jetting drain cleaner. Once an entrance is found, it's also possible to excavate a new drain from the outside and perhaps connect to a town's storm sewer system.

With the ever present possibility of power outages, relying on a sump pump is not a recipe for peace of mind. By all means, do whatever is possible to divert water away from the house on the outside, but don't try wholesale excavation around the foundation. The real akey is to re-develop or create a means for the water to escape from the cellar on its own.

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