Great Lakes Waterproofing Basement Waterproofing

Types of blocks used in basement walls

Thu, 11 Jun 2026 17:12:57 GMT

Some types of concrete blocks used in homebuilding

Modern foundations are usually made of concrete, either solid (poured) or blocks (CMU). These are the sizes we typically see but, the older the home, the more variation we see. Some builders used to make the blocks right on the building site with molds and a mixer.

While the hollow cores add strength, they also can hold up to 1.5 gallons of water each! A normal city home might be 30' on one wall. 20 blocks x 9 high = 240 gallons of water space! No wonder some walls are spraying water when it rains

A great view of why basements leak water

Thu, 11 Jun 2026 16:56:15 GMT

A great view of why basements leak water

This is a great photo of why basement walls leak! This is a basement egress window from around 1970. We don't see a lot of larger basement windows from back then and the surrounds are usually made of block or solid (poured) concrete.

If you can see a crack on the inside of your basement, it will go all the way to the outside. The rock landscaping can hold 100's, if not 1000's of gallons of water, basically a moat around your home.

Over time the water will also bring sand/dirt with it creating a low spot at the crack, a perfect nature funnel into your basement.

The owner tried putting a concrete patch on the inside but the only long-term solution is to address the crack from the exterior, there's just too much water pressure pushing through the patch.

Pouring a basement footing 1940

Thu, 11 Jun 2026 16:51:08 GMT

Pouring a basement wall footing in 1940

Pouring a footing back in 1940, they were usually around 24" wide and the foundation wall was built on top of this after it hardened. After the walls were built the inside basement floor would be poured last.

Rubble Basement Wall Construction

Thu, 11 Jun 2026 16:37:55 GMT

Rubble Basement Wall Construction

At one time stacking square stones was very popular for foundations, we call these rubble walls. This method was used on budget farm builds and big-dollar mansions.

Unfortunately the mortar used to seal between the rocks starts to degrade over time and in some cases allows water to move through the walls.

In our opinion, bentonite injections around the exterior foundation is the best way to seal these back up. Not only are you stopping the water outside but you don't have to cover the inside walls with plastic sheet or dimple board.

Drain Tile Hall of Shame

Thu, 11 Jun 2026 16:32:23 GMT

The Drain Tile Hall of Shame

One of our hall of shame photos, dimple board drainage down into a drain tile system.

We started to see this product over the last five years grow very popular along with heavy-duty plastic sheets to help channel the water into the floor. Most of these are made with HDPE (high-density polyethylene) made from oil.

Standard polyethylene plastic sheeting (like standard poly rolls) for indoor basement waterproofing or vapor barriers presents a significant fire hazard and violates most building codes. Because standard poly is petroleum-based, it can melt and burn rapidly if exposed to a flame.

The International Residential Code (IRC) dictates that any exposed plastic used as an interior finish or vapor barrier must be flame-retardant.

Minnesota Building Code 26 (2020) goes into it a litte bit but we might see changes in the next edition. It looks like your ok if you have 1" of concrete over it. (this only talks about foam insulation).

2603.4.1.1 Masonry or concrete construction.

A thermal barrier is not required for foam plastic installed in a masonry or concrete wall, floor or roof system where the foam plastic insulation is covered on each face by not less than 1-inch (25 mm) thickness of masonry or concrete.

Is this a code violation?

Basement Block Wall Construction

Thu, 11 Jun 2026 15:41:21 GMT

Basement Block Construction

A side view of a common basement block wall you might see in Minneapolis or St. Paul. Typically it's 6'-8' from the drain tile pipe to the grass. The three concrete parts, footing, wall, floor are built at three separate times, footing first, wall second, floor last.

The space between the bottom block going into the floor area is called a "cold joint" meaning wet concrete is layered on dry concrete. This space is notorious for being porous and allowing water to flow through.

Water will enter that central hollow core and when there's enough of it, the pressure of the water column will push the water into the basement floor area.

This is not from a "high water table," it's called "grade level" water. but it looks like it's coming from below the home. Water from a high water table tends to last for weeks, not days.

Mortar Joints

Thu, 11 Jun 2026 15:33:05 GMT

Basement Wall Mortar Joints

Are you seeing nice uniform concave mortar joints in your basement walls? This pushes the mortar in and compacts it plus it looks great!

We've found walls with unfinished or poorly done joints to be less waterproof with more mortar damage. If it looks unfinished inside the basement, the outside finish is probably worse. With time, water and the freeze/thaw cycle will find ways into the blocks and eventually your basement

Welcome Spring 2026!

Thu, 26 Feb 2026 22:37:52 GMT

Welcome Spring 2026!

It's getting close to that time of year in Minnesota when the snow melts, the ground thaws and, unfortunately some of our basements leak.

We have pretty severe conditions in Minnesota and our foundations take a beating, a wet basement is not a question of what, been when. The constant freeze/thaw cycle puts a ton of strain on foundations causing cracking or holes. Add in snow melt and you have direct water entry into your basement.

Great Lakes Waterproofing has been serving the Midwest since 1978 and serving Minnesota and the Twin Cities since 2006, we are locally owned and operated. Specializing in exterior waterproofing, stopping water before it moves through your walls for Real Waterproofing.

Yard Water Drains are Backing Up

Mon, 24 Mar 2025 22:37:19 GMT

Yard Water Drainage Blocked Up.

Great Lakes Waterproofing is a big fan of underground yard drain systems but the cheap undersized plastic pipe we find at most home stores can be a challenge if not properly maintained. This Burnsville, MN Homeowner spent thousands fo dollars putting this underground water pipe drainage system in but over a few years it filled with dirt, preventing the water from draining.

This lead to water pooling up at the foundation causing significant basement water damage. We recommend these pipes need to be much larger in diameter, minimum 6" of diameter and properly cleaned at least once a year to get all the dirt and leaves out.

HELP!!! My Drain Tile is Not Working

Thu, 01 Sep 2022 21:50:50 GMT

I Have Drain-Tile But I Still Have A Wet Basement!

Beaver Dam Waterproofing

Fri, 26 Aug 2022 22:24:25 GMT

Basement Waterproofing Using Above Floor Channels and Dimple Board

Basement waterproofing using a channel installed at the floor level dates back to the late 70's, around the same time drain-tile started gaining popularity on existing homes with wet basements in Minnesota. These are commonly known as beaver dam or cove waterproofing systems and a lot of home owners went with the system because of it's low cost. The popularity really dropped after the 90's but we're seeing new versions of this system start to pop up again.

Great Lakes Waterproofing has installed similar beaver dam systems in industrial settings, but these are a really bad idea for wet basements. For industrial applications, ripping out 18" thick concrete for drain-tile is not possible, it's thick for structural reasons and you wouldn't want to compromise the foundation. They are not covered with new walls so they are easy to maintain if a leak occurs.

The beaver dam system consists of two pieces of plastic, screwed to the wall allowing water to flow to a sump basket, or sometimes they just flow to the floor drain (this is a code violation). Special corner pieces and seam covers help keep the water in the channel. Holes are drilled into the wall so water can escape the hollow wall and drain into the beaver dam system. After the system is installed caulk is used to seal all of the joints, and there can be a lot of them.

The main problem with a beaver dam waterproofing system is there's no slope! Most of the time it will have standing water in it, the blocks will also not be fully able to drain and can have close to a gallon of water in them before they drain into the channel. Guess what, your wet basement now smells like a moldy, musty, mildew'd rag. This is also a perfect place for basement mold and mildew to grow.

How Can I Help With My Wet Basement

Fri, 26 Aug 2022 00:46:11 GMT

How The Homeowner Can Help With A Wet Basement

The first question we get asked is "how can I help?" While the Great Lakes Waterproofing System works in nearly all applications, there are steps that can be taken to help insure that the basement dries up completely. The most common problem is improper drainage away from the structure, make sure gutters are attached properly and the extensions are long enough to clear all obstructions including patios, sidewalks, trees, etc.
For a typical mid-size house 1/2" of rain on the roof will be over 150 gallons of water, some houses only have two downspouts so over 75 gallons of water could be concentrated in one area. This is why it's crucial that the water is channeled away from the structure and not left to saturate into the ground near the foundation. Our experience has shown that even placing plastic on the ground around the house does little to channel the water away if other steps are not taken first.

Another place overlooked is the window wells. The gravel should be at least 4" thick and about 8" below the bottom of the window. Over time debris builds up in the wells and if not cleaned out will provide water an easy entrance between the window frame and the wall.

Last but not least, observe the concrete and pavers around the house. Over time these will settle (usually sloping towards the house) providing a funnel of water right into the basement. Look for the tell-tale signs of dirt and sand built up on the concrete or pavers. Proper surfaces should be slightly above the ground with a slight slope away from any structures. Large voids will develop under concrete, asphalt or pavers, that's one of the reasons its sinking. Exterior Basement Waterproofing will fill these voids, stabalizing the soil and prevent water from building up in these areas.

Types Of Foundations

Fri, 26 Aug 2022 00:29:44 GMT

Knowing Your Type of Foundation Will Help With Basement Waterproofing

THIS IS NOT OUR WORK!!!! This is a customer's recently installed drain-tile system that is not working.

Most of our work involves waterproofing structural foundation walls. Using our injection equipment we saturate the ground with Bentogrout Hydroclay filling voids, holes and cracks that have formed over time allowing water to build up and enter your basement or lower level.

The most common walls we encounter are block (as seen above), which can be hollow cinderblocks or an much older solid block, both need a concrete mortar for a binder. Block walls will leak when foundation settling happens, very small hairline cracks will develop and are large enough to let in large amounts of water with a strong rain storm or snow melt. In some conditions, the blocks will develop holes, these can be small like a dime or much larger like a softball, we usually see within this range.

Basement Waterproofing With Bentonite

Thu, 25 Aug 2022 23:47:35 GMT

Exterior Basement Waterproofing is Real Waterproofing!

We stopped posting on our Blogspot Site, some of the posts go back to the mid-2000's, these are some of the highlights.

For over 44 years Great Lakes Waterproofing has been providing one of the most exciting basement waterproofing methods for home and business owners. Using our exclusive technology we inject a waterproofing blend of bentonite (Bentogrout) into the area around the exterior basement floor and walls. In most cases this can be done from outside with nearly no damage to the existing ground cover.

Once the Bentogrout Hydroclay has saturated the ground, filled in voids and small cracks in the concrete walls, it begins to absorb water and solidify to a consistency similar to thick peanut butter, providing a permanent barrier against water. If your construction is new or you've exposed the wall we can apply benonite panels and membranes directly to the wall (and under the footings and floor if needed) giving you the best waterproofing possible, we call it Real Waterproofing, stopping water outside your basement.

While methods such as filling cracks with mortar, applying an epoxy-base paint or a drain-tile type system help with diverting water, they all have one similar yet critical component...They still let the water through the wall before it gets stopped. The damage this causes to the wall continues as long as the water is present. Settling of the wall and mortar damage on block wall will continue requiring on-going maintenance. Radon, mold and mildew will still be present and since your increasing the incoming water flow, you may even be making it worse.

Basement Waterproofing using all-natural bentonite has been successful in many different applications, our blog will have case studies on several of these applications and the questions we encounter from time to time.