How Not To Waterproof Your Basement or Foundation

There has been a comeback of the beaver style waterproofing system using dimple board, a plastic membrane with dimples on one side that keep it off the surface of the wall.

Beaver style waterproofing was similar but used flat rigid sheets of plastic attached slightly off the wall so water can flow through the wall and down to either a floor/wall channel (cove system) or even to an underfloor drain tile system.  We see a lot of old 80's beaver dam waterproofing in Minneapolis and not only do we see it but you can smell it walking down the stairs.  Why?  The system allows water to flow on the walls and it never seems to fully dry behind the plastic sheet or dimple board since there's little air flow.

We looked at several dimple board/mat manufacturers installation brochures and not a single one mentions using this product for interiors, it is meant to be used outside.  We call this style of product a Mold Factory, lot's of nasty things grow on that wet dark side of the plastic.  If this is used indoors, it's especially important to seal all of the edges so no fumes and other nasty stuff can get into the basement (there is no seal at the top of this product).

Why not STOP THE WATER on the outside instead of going to all this trouble, exterior waterproofing is usually much less expensive.

This homeowner put dimple board 1/2 way up the basement wall and drains it into a home-owner installed beaver dam or cove system that is mounted on the basement floor.  In the far corner is the sump basket and pump.

These systems might work initially, we usually see them after they've been used a few years when the real leaking start.  The system has several red flags, the caulk or glue used to join the pieces has a lifespan of 3+ years, the peeling caulk will let all kinds of water out.  Since these system sit on the flat floor, they always have water in them, there's no slope to the sump basket.  These can be perfect mold factories, the wet dark space might also become really smelly.  If the basement isn't finished, it might not be a problem but usually it's covered up and very hard to repair without ripping a lot of stuff out.

This system is a floor mounted cove waterproofing system with plastic panels mounted on the wall.  The idea is that water will flow through the wet basement wall, but not through the plastic sheet.  It goes doen into the cove system which drains into a sump basket and pumped back outside.

In Minnesota, with our normal rain conditions, these systems never seem to fully dry out, guess what likes wet dark areas?  Yep, mold and mildew, it's so bad on this home that it's growing on the inside walls.  Most caulk products used to seal this when new only have a lifespan of 3+ years, luckily this homeowner never finished this basement but they wanted to fix the wet basement.  Exterior waterproofing stops the water on the outside for Real Waterproofing!

We call this a cove, flume or beaver dam system.  This system became really popular around 1980 and could be installed by a professional or a homeowner.  Holes are drilled in the bottom blocks, the plastic channel moves the water to a sump basket or the floor drain.

We install these systems, ours are used in non-residential buildings where the floor might be 12-18" thick and drain tile is not an option, we use concrete to encase them because over time, the caulk peels off the walls and they leak.

The main problem is that there is no slope so water never fully drains, these can have a very strong odor if the water sits for a long time.  While they work for awhile they must be maintained and should never be covered with drywall.

We've seen some basements where the contractor or home-owner used either spray or foam insulation to act as a water barrier.

Unfortunately it doesn't work, just like paints and coatings on the inside don't like to stick long-term to old foundation walls, the insulation will also start separating from the basement wall and water will flow down to the floor like in the photo.

If you look at the side of the window, this foundation is a stone or rock foundation, found on homes built before 1920.

This one is leaking pretty badly, the concern is mold and mildew building up behind the insulation and this basement can't be finished in this condition.

This basement foundation wall is only a few years old, this is a very common issue we see with newer construction, the foundation wall has a vertical crack from the basement floor to the ceiling.  Water loves the path of least resistance so it comes out through the middle of the wall, bypassing the underfloor drain tile system.

The original contractor "fixed" the issue with an interior waterproofing paint, there's many different versions of these and we've seen failures with all of them.  After a few years the contractor has no liablity, these products will usually get them over that time frame.

Unless the wall is brand new, interior paints and coatings have a hard time sticking long-term to crusty walls, just run your fingers on your wall and you'll probably pull off sand and grit.

Here's a close up of the "waterproofing" coating put on the wall, it worked great for a year of two but it's too rigid and it split over the crack.

Everytime it rains, water moves through this basement wall crack and hits the floor, luckily this homeowner hasn't finished the basement yet and they were able to see the water before it destroyed wall coverings and insulation.

Great Lakes Waterproofing used exterior "no-digging" waterproofing on this crack.  By targeting the source of water, we stopped it on the outside.

We also are trained Fortress Carbon Fiber Installers, we can also "staple" the crack on the inside to help stabalize it from further separation.