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04/22 - Renovation

How Does Basement Waterproofing Work?

Your Guide to Basement Waterproofing |

Basement Waterproofing 101

It has become quite common for basements to be part of a family’s day-to-day living space. Oftentimes, you’ll hear of it as the playroom, rec room, den, nanny or in-law suite, basement apartment or man cave. Whichever name, it is no longer the norm to settle for those low ceiling height, dark, dank, unfinished areas. Gone are the days of basements for your laundry and storage of things you’ve lost interest in. And with this intention, that’s where knowing about basement waterproofing comes in handy. Move over spiders, furnace, and water heater. Do you know how expensive real estate is?! We need this space!  


Embracing Basement Living

For those who purchased a home that was built in the last fifty to sixty years, basement dwelling may already be taken into account. This means, your basement might have a proper ceiling height, heating/cooling supply, bathroom and maybe even a second kitchen or separate entrance/walkout. That was the era when people started to embrace basement living (tiki bar, anyone?).

So, when do you have to worry about a potentially leaking basement? You may have some moisture issues down there, but less so than owners who bought something older. Anyone with an unrenovated home from before the 1950’s will typically describe their basement as having a low ceiling, foundation walls, thin concrete slab flooring (in some cases still dirt!) and some posts and beams. It’s also likely to have exposed radiator, plumbing pipes and electrical wires along and between the joists. Back then, it was simply cold storage, maybe a coal chute or an oil tank. No one really thought about using it in the ways we do now.  


Waterproofing Your Basement

If basement living was considered in the design and build of your home, you may have less basement moisture issues than older homes. However, like many of us in Toronto, we are dealing with older homes. And based on a number of unique factors, your home may have a damp, musty, or downright wet basement. What are your options?  


Option 1: Exterior Basement Waterproofing

A common option is to waterproof the exterior foundation walls. This involves digging down to the foundation of a home and applying a watertight membrane to the exterior of your basement walls. There are a number of different products or combinations that can be used. This includes liquid form, peel and stick, or a plastic membrane system to name a few. Once the product is successfully applied, water can push up against the membrane, but will run down or away. It would then be absorbed as ground water once it is lower than the footing of your home.

If your basement is already finished and in use, you may want to control and stop water from entering your home using this system. This will help to avoid the added cost of removing interior finishes to get access to the basement walls. If water has not already damaged the internal materials (wood, drywall etc.) and the exterior work is successful at keeping the damp out, it may be the best choice for your situation. However, you may need to re-do some of your landscaping after all of that digging around the entire perimeter of the structure.

One reason why more people don’t use exterior waterproofing as the solution is access and proximity. Many older homes are row or townhouses. Or, they’re too close to the neighbours to successfully waterproof all of the exterior ways that water could enter. Also, basement floors are concrete and therefore porous, meaning water can pass through it. So, the old floors can remain a weak spot even when the exterior basement walls have been sealed. If the local soil is constantly damp, simply sealing the walls from the outside may not be enough.  


Option 2: Interior Basement Waterproofing

The second option is to install a water management system in your basement. This allows the water to enter the home through the original or new walls, while controlling where it goes. This way, it does not do damage to interior finishes.

How? Apply a seamless waterproof plastic dimple board to the interior side of the basement walls. This carries any water penetrating down the wall and into the floor before it gets to your framing, insulation and drywall. From here, it reaches a weeping tile to carry that water to the sump pump. Then, it ejects the water back to the exterior of your home. Instead of sealing your home from the outside, you are sealing from the inside.

This option is very different from the exterior seal. It requires a lot of work to the inside of your basement, including burying the weeping tile and sump pump in the basement floor. You’re removing previous finishes from exterior walls to apply the membrane material. For finished basements, you’ll likely re-do most or all of those finishes. If the work is that invasive, you may want to explore investing in more ceiling height from digging the basement down in the form of underpinning or bench footings followed by re-pouring the floor for a cleaner, drier, smoother, more level slab. While you’re at it, you could add radiant heat to the floor to make the basement even more comfortable and inviting!

Redoing the basement to this extent also allows you to replace your home drainage system (it may be clay pipe). Or you could add a backwater valve, which is another way of keeping an additional source of water at bay.  


Home Renovation Permits

If you plan to take on home renovations, be sure to contact your insurance company about any upgrades you elect to make. There may be savings to your home insurance plan as a result.

It’s part of my job as the writer to also remind you to get all necessary permits for any work you do to your home. Underpinning and bench footings are structural projects that require proper drawings and inspections. And, this should be handled by the necessary professionals.  


A Final Thought on Basement Waterproofing

Lastly, a final thought on the moisture in your basement before you begin any planning on a major project. Use common sense and have a look at what the source of the basement moisture may be. For example, as real estate agents, we order and review home inspections all the time. One thing these inspections are constantly reminding us of is the need to move water away from foundation walls. Have a look at these possibilities:

  • Inspect your eavestrough system with a roofer: could it be better? Is it dropping all of the water collecting in your roof (from a summer super storm) right at the corners of your property where it finds a way in?
  • Is the flowerbed at the front wall of your house (that you deep soak every summer evening) the potential source of the water in the furnace room?
  • Are you getting ice-damming around the basement windows in the winter months causing water to get into places it normally wouldn’t or couldn’t?
  • Does the ground around your house all grade (slope) towards the walls or away from them?

Know what you are up against. Some preventative maintenance can go a long way to solving or slowing the issue.

The right approach for basement waterproofing will depend on your budget, access, and water situation. This is determined by you and the company you wish to retain for the project. It may not be easy or inexpensive, but it can add value or improve the quality of your living space. If you’re in the market for a property with an unfinished basement you can put your own personal design stamp on, let us know. We’re also here to answer any questions about selling a home with a questionable basement (or a great one, we like them all).

We’re always happy to chat all things basement. It’s one of the FOUNDATIONS of our business! #sorrynotsorry #dadjoke  


This article is written by Fox Marin Sales Representative, Ian Busher. With an extensive background in carpentry and contracting, Ian is our resident “Renovations Expert”! He takes pride in his ability to assess the quality and condition of a house. This, in tandem with his talent for speaking to the feasibility and cost of potential renovations, and his eye for the aesthetic details of a property, makes him a powerful partner for anyone looking to buy a home in the Toronto real estate market.