Sorry, this is a long one, a 2-parter. It’s a drainage question, so I thought the exterior message board would be the place for it (even though it’s about the basement).
We have a 75 year old home in Halifax, NS, Canada. We decided to waterproof our leaky basement, and had a contractor do the job. Unwisely, we chose the guy who gave the lower estimate. They took out a square foot of dirt (and corroded pipes, more about this in Part 2) from the inside perimeter of the foundation walls, laid a perforated drainage tile pipe, crushed stone, a dimpled waterproofing membrane, and cemented it over. We’re very unimpressed by the contractor, and we have little reason to be confident in their abilities, and we can see that they were careless about a lot of things. However we have had a major rainfall since they did the work, and the basement is dry. I understand that this is a common way of waterproofing older basements. My first question is: is this an idiot-proof method? Right now it seems to be working fine. We did not inspect the job before they put concrete over it. If they did a bad job of it (say, for instance, they didn’t dig the trench deep enough in some spots, or they left a gap in the drainage tile pipe), would it be immediately apparent during the first bad rainstorm, or might it break down 20 years down the road? Rather than face disaster down the road when the basement is finished, should we break up the cement and inspect the job if we’re not confident in it?
My second concern has to do with our gutter downspouts draining into this system.
I don’t know if it is unique to Halifax, but for most homes in the city the gutter downspouts don’t empty onto our lawns, but come down and enter into the basement and drain into the sewer system. The downspouts enter into the basement at 2 feet above ground level, becoming 6 feet above the basement floor level, travel down into pipes under the basement floor and eventually into the sewage system. In our case, we had downspouts coming in at the four corners of the house; all of the underfloor pipes were corroded and leaking.
We decided for aesthetic reasons to maintain the downspouts coming into the basement, rather than rerouting them to drain onto the lawn. The contractor is confident in their solution, saying that the drainage system will have no problem taking in the rain water. We have some concerns with it.
I’ve attached a photo and a diagram of what’s going on. The original metal pipe coming down to the basement floor was broken off when they put in the trench. They attached over it a larger piece of PVC pipe, which drains into the crushed rock. Three of the four downspouts look like this - they do not yet have concrete over the crushed rock - but one is covered over with concrete and thus inaccessible.
What I’m worried about is when or if leaves drain down the pipe. Before this, the leaves probably would have been pushed through to the sewer no problem. Now they would get stopped at the crushed rock, form a barrier and start flooding upwards. Even if we were to extend the downspout through the crushed rock to connect into the drainage tile pipe, leaves would eventually clog that too, wouldn’t they? Another possibility is to put a screen in up higher to catch the leaves. But isn’t that calling for disaster, if leave clog the flow of water there? And, in this case, would dirt and small debris coming through the screen also get caught in the crushed rock and start clogging?
It would be less than ideal to have to perform routine maintenance on this, but we could leave it how they have it, and every year or two detach the PVC pipe and clean out anything that’s there (in the fourth corner that’s inaccessible, we’d have to break up the cement to do this).
Right now I’m leaning towards the most extreme solution that would solve both my part 1 and part 2: to break up the concrete they laid over their work, check everything over, and lay in proper pipes, alongside the drainage tile pipe, that would connect the downspouts to the sewage.
Thanks you very much.