French Drains

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nobbie48

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A relative waterproofed their basement from the inside using the French drain method, the waterproof liner is on the inside.

I did mine the hard way having the outside dug up and all work done on the exterior so no moisture is against the blockwork.

Is there any special procedure for finishing the interior of a basement with the French drain system? Links?

I worry about mold.
 
This thread comes at a perfect time as I discovered my house has a leak in the basement.
 
We ended up doing, outside, then inside and a sump pump. All our new materials, wood, drywall, etc. were mould resistant.
 
Get a pro company in to spray foam (after framing, electrical, etc.)

Spray foam-ing the rim joist yourself with 2" XPS foam board on the walls is an alternate, along with 2x4 stud walls and roxul insulation.

Dricore or Amdry as a sub-floor with vinyl plank flooring or engineered hardwood.


Here's the definitive reference: http://buildingscience.com/documents/bareports/ba-0202-basement-insulation-systems/view (download the document)
 
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A. was the French drain done by a drain company or a contractor that 'knows how it works' ? there is usually a plastic coping that goes as part of the system to cover the interior drain channel. You just need to stay clear of that.

B. Put a hygrometer in the basement for a week and see what the relative humidity is in relation to the rest of the house.

C. there are 25ways to finish the space, and everybody has an ok idea.

I always worry about mold even in a pretty dry basement, I would use a rigid foam insulation, the blue wood studs, isolate all framing from direct contact with the concrete and probably use a version of DryCore flooring. I'd build inside the wall and sacrifice some sq ft to keep an airspace between the concrete walls and the framing to ensure any water infiltration goes straight down to the drain channel.

sometimes those French drain solutions are pretty neatly done, others look like they were cut with a chainsaw and sledge.
 
Save on the Dri-Core flooring cost by buying rolls of platon plastic external foundation wrap, 4'x8' sheets of 5/8" tongue and groove OSB, and 1/2" rigid foam insulation boards.

That gives you a Dri-Core type floor that can drain away any water that may seep in, tighter vapour sealing, and a warmer floor than even insulated Dri-Core will give you, all at about 1/2 the cost of Dri-Core.

You'll be able to put anything you want over the OSB, engineered wood, vinyl plank, carpet, and even a piano on top of all that. Interior partitions can be built on top of the OSB subfloor.

See https://www.armtec.com/wp-content/uploads/Platon-Subfloor-Installation.pdf for instructions. The instructions don't discuss the foam insulation board, but it would just lay on top of the platon and under the OSB.
 
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crankcall said:
A. was the French drain done by a drain company or a contractor that 'knows how it works' ? there is usually a plastic coping that goes as part of the system to cover the interior drain channel. You just need to stay clear of that.

B. Put a hygrometer in the basement for a week and see what the relative humidity is in relation to the rest of the house.

C. there are 25ways to finish the space, and everybody has an ok idea.

I always worry about mold even in a pretty dry basement, I would use a rigid foam insulation, the blue wood studs, isolate all framing from direct contact with the concrete and probably use a version of DryCore flooring. I'd build inside the wall and sacrifice some sq ft to keep an airspace between the concrete walls and the framing to ensure any water infiltration goes straight down to the drain channel.

sometimes those French drain solutions are pretty neatly done, others look like they were cut with a chainsaw and sledge.
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The job was done by a plumbing /drain contractor and inspected by the city. The workmanship looks neat.

I will suggest a hygrometer but paper left down there still feels crisp not limp, a good sign.

The job was done 1-2 years ago and there's no indication of a problem but the place is all open space. The concern is humidity getting trapped between the block and the bubble barrier, creating mold and finding its way out.

Maybe I'm paranoid but a buddy's neighbour at the cottage had a water leak go unattended and a three year old cottage has to be torn down and everything in it scrapped due to mold.
 
FLSTC said:
Get a pro company in to spray foam (after framing, electrical, etc.)
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+1 This worked for me.

Had it dug on the outside 3 times and it still leaked. Had a contractor do the inside 5 years ago and it was perfect. The drainage membrane was covered with a thick latex type substance and it drains into the drainage under the house. I wanted to make sure it was fixed so I left it uncovered for 2 years and eventually finished it with Blue Wood, spray foam and mould resistant drywall. It was warm and the relative humidity was around 35%.

They of course the wife wanted to move :(
 
Using the dimple drain board in rolls is cheaper and OK, just make sure its suitable for interior use. Some stink and off gas and cant be used indoors, it will be stamped on the product.
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