Thread: basement floor waterproofing?

I saw this at a home built in 1926. The egg carton-like strip went around the whole basement floor perimeter, with concrete added afterward to make the edge of the floor slope up a little toward the strip. The new homeowner said the previous one had it installed as a measure to keep water out of the basement. I've never seen anything like it. Can anyone tell me whether it's an accepted method, and what purpose the strip serves? Is it like a kind of flashing? Indicative of drain tile underneath?

Thank you!

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Originally Posted by Kristi Silber

I saw this at a home built in 1926. The egg carton-like strip went around the whole basement floor perimeter, with concrete added afterward to make the edge of the floor slope up a little toward the strip. The new homeowner said the previous one had it installed as a measure to keep water out of the basement. I've never seen anything like it. Can anyone tell me whether it's an accepted method, and what purpose the strip serves? Is it like a kind of flashing? Indicative of drain tile underneath?

Thank you!

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Helps collect and channel water, usually in conjunction with a sump pump.
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Those tiles look like 9".

Most 9 inch tiles contain Asbestos.
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Its drainage mat, comes in rolls, can be cut to various sizes, and is used to channel water towards a drain tile, weeping tile, or similar material where it's centrally collected and re-deposited elsewhere. It is also used on exterior foundation walls.

Kristi,

Are you still here? Didn't we scare you away yet?

I have seen that used on the exterior of a foundation wall. As a part of a curtain drain that ends over a perforated pipe at the base of the wall to divert subsurface soil to a drainage system. I have not seen it used flat and wonder if that is an approved installation.

"Are you still here? Didn't we scare you away yet? "

Persistent bugger, ain't I?


Well, duh...I just last weekend saw a talk at an ASHI meeting that showed a similar set-up, and only now made the connection. Different edge material, but same principal, more or less. The stuff used by these guys helps keep radon from entering the basement (part of a system called SafeBasements).

Thanks, guys!

Around here we call that a french drain. Very common install type for basements with wall seepage issues. Generally works well at keeping the basement floor dry. It doesn't however resolve the water problem itself, only redirects the water. Agents always get pissed when I explain that to the client.
Sometimes its also installed as a scam. If you only see an 1" or so of concrete repair along side the mat its probably a scam install.
For a legit install you should see at least ~1' of concrete repair around the perimeter. Also look for the sump pit. For what you do you probably won't be checking the pit for proper install, etc. However at least make sure whether there is one or not. Pay close attention to where the sump discharges to. I always think its funny & stupid when the sump discharges 3" outside the wall.

Yep, has a sump pump. I'm embarrassed that I didn't put it all together before...well, I sorta did, but didn't know what role the drainage mat served.

And yep, Markus is right that sump pumps aren't things I normally examine closely, nor do I know much about them. This one appears to have an AC battery as a backup power source. It happened to be included in my "general basement photo," which is why the (cropped) photo of it is so small.

At least there appeared to be more than 1" of concrete over the trench.

This one discharges into a pipe outside, which I imagine goes to a dry well or the municipal sewer system. Didn't even notice it when I was there! I'm so focussed on looking at other things, and doing it as efficiently as possible, there's a lot I miss. $26 to perform and write up an interior and exterior inspection is not conducive to dawdling, which is one reason I appreciate this forum and the people who post here so much!

Kristi, As a rule, any basemnt system is not allowed to pump water into a municipal drain, storm or sewer.
Drywell, woods or neighbors driveway
thoughtbyou scared me away didn't you?

What?! Scared you away? Nah, I did my best, but fortunately you've got thicker skin than that.

You know, I knew that about draining into the sewer being a no-no, at least around here. I don't know what I was thinking. I haven't been thinking much throughout this thread, I'm afraid.