How to Waterproofing Stone, Limestone and Rubble Basements and Foundations

Some of the oldest building foundations are made from stacked stones and rocks, either round or square, we usually see round "field stones," square limestone or stacked rubble in the Midwest. 

Stone foundations can last a very long time but it's weakness is the mortar used to fill in the spaces between the stones.  While the stone will be fine, after decades, the mortar used, starts to disintegrate and feels sandy to the touch. 

Water starts working it's way through the joints and sometimes even the porous limestone rock itself and you end up with a wet basement area.

Plastic sheets and drain tile should only be used in extreme conditions. It is not the correct way to waterproof stone walls!

It is very rare to see a stone wall have what we would consider a traditional concrete footing, in some cases they're larger stones.  For some foundations, they use the bedrock, and some are just rocks on ground.  Most of these walls we see leaking from above the basement floor level which means a drain-tile system will not work without a drainage mat placed on the walls.

This method of waterproofing (we call it water-management) was popular when remedial waterproofing got off the ground in the early 1980's and lasted a few years before it disappeared.  Recently we've seen several newer "waterproofers" using plastic sheeting inside the basement to help capture the water and drain it to a floor cove channel or underfloor drain tile system.

The stone, especially limestone, and mortar can be very porous, we like to see this area breath otherwise your containing a lot of moisture in this area.  With a plastic barrier up, mold, mildew and radon can build up and over time, holes will develop.  I can go in an 80's basement with plastic wall barriers up and immediately smell mold and mildew, usually it's a pretty strong odor and can be very dangerous with long-term exposure.

Following the water, a chunky Bentonite Slurry is pumped around the exterior of the foundation moving through holes and cracks in the basement wall.  Over time the bentonite thickens and sets up like a flexible clay forming an exterior barrier against water.  Exterior waterproofing is Real Waterproofing because it stops the water outside of your basement or foundation.  Older homes and businesses in Minneapolis and Saint Paul may have these stone or limestone basement walls, Bentonite Exterior Waterproofing is the professional solution to your wet basement.

It can get a little messy inside with these types of walls but we'll clean up the bentonite once done.  Great Lakes Waterproofing will seal the injection holes and clean up the area.  Dimple board and plastic sheets should not be used in these stone-wall basements, they just capture the water and direct it to a sump basket which just pumps it back outside.  Exterior water damage to the foundation wall continues and a breeding ground for mold and mildew might be established.

Ok, sometimes we have to do work on the inside, this wet basement foundation went deeper than most basements and the only way to hit the wet areas was to pump through the walls.  Using the same process, a chunky slurry of Bentonite Exterior Waterproofing is pumped through the limestone walls, void-filling the outside dirt and stopping water outside of the basement.  No need for a sump pump and basket, Real Waterproofing stops water before it moves through the walls, usually at a fraction of the price of a drain-tile system.

Wet Limestone Basement with DryLok Waterproofing Paint

Oops, looks like we have a failure with the waterproofing paint.  Unfortunately coatings on the inside will rarely fix inside basement leaks especially when the mortar starts to fall apart.  The paints have a hard time sticking long term and with more than minimal water pressure will just peel off the wall.  It can look great when new if your trying to brighten up the basement but in most cases, they are not an acceptable Real Waterproofing Product.

Over time water has worked it's way inbetween the foundation stones and taken the mortar with it leaving big holes in the basement wall.

This stone basement wall was exterior waterproofed, the chunky bentonite sealed up the water pathways, holes and voids, stopping the wet basement issues.  The bentonite will fill voids and water pathways in the soil and even bond with dirt and sand creating an all-natural barrier against the water.

While this foundation isn't Limestone, the other part of this historic building is and this poured concrete basement wall has to be around 100 years old, maybe more.  This was about 12' down from grade level with a patio area above which made going through the inside necessary.

Previous waterproofers had put in drain tile pipe leading to sump basket and pump.  They had then put up plastic sheets on the wall to channel water down to the pipe.  This doesn't waterproof the walls, this just brings the water in and it gets pumped right back outside.  Unfortunately this wet basement was getting mold from the humid conditions, ideal for mold and mildew growth.

While pumping a chunky mixture of Bentonite through the wall into the outside dirt, water could be seen coming in through the many holes in the wall.  Eventually the benonite will fill the exterior voids and the water will stop moving through the basement wall.

It looks like Great Lakes Waterproofing has made a mess in this 150 year old wet basement with a limestone wall, but we call it "finding the sweet spot" one of the many holes in this basement wall leaking water.  The bentonite will thicken up and cork up this hole, a concrete patch will be applied on the inside of the basement wall and the homeowner can enjoy their walls without a silly plastic wall barrier put up.