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Dig Once, Do It Right
You’ve probably heard the old saying, “Don’t fix the roof when it’s raining.”
Well, here’s a basement version of it, “Don’t wait to waterproof after you’ve already lowered the basement.”
We’ve seen this play out too many times across Toronto. A homeowner gets excited about increasing their ceiling height, adding value, turning that dark dungeon into a livable space. The crew comes in, does a great job lowering the foundation, the concrete’s poured, and then, weeks or months later, the water starts creeping in.
By that point, you’re no longer protecting your investment, you’re repairing it.
Let’s talk about why waterproofing and underpinning should go hand-in-hand, especially in an older city like ours where Victorian charm often comes with 100-year-old concrete and questionable drainage.
The Toronto Reality: Old Homes and New Problems
Toronto’s got personality. Walk around neighborhoods like The Annex, Riverdale, or Leslieville, and you’ll see it in the brickwork, the porches, and yep, the basements.
Most of these homes were built before anyone was thinking about finished basements or rental suites. Back then, the foundation walls were meant to hold up the house, not keep water out. That’s why when you start digging below the original footing, you’re opening a whole new can of worms.
Lowering a basement can expose weak points in the structure, make the foundation more vulnerable, and shift how groundwater interacts with your home. That’s why it’s the perfect, and frankly, only smart time to deal with waterproofing.
Doing one without the other is like building a deck and skipping the weatherproof stain.
Why Waterproofing Later is Way More Expensive
Let’s get real about timing. Once the concrete slab is in, and the walls are sealed, your waterproofing options shrink, fast. Here’s why:
- You’ll need to break up the new floor just to access the interior.
- Any exterior fixes might require excavation, which isn’t cheap in Toronto.
- Leaks won’t always show up right away, they creep in slowly, damaging drywall, paint, insulation, and your wallet.
We once had a client in East York who lowered their basement in early spring. They figured they’d “deal with moisture later.” Come November, we were called in after their finished space got soaked during a thaw. Not only did we have to rip out the new flooring, but mold had already started creeping up behind the drywall. Cost them double. And it could’ve been avoided.
Good Contractors Always Pair the Two
If your basement underpinning contractors aren’t talking about moisture protection when planning a foundation-lowering job, that’s a red flag. A good team, like ours, knows the soil conditions in areas like Roncesvalles or Forest Hill aren’t always friendly. Some spots have higher water tables, others are more prone to hydrostatic pressure. That pressure can build up behind your new walls and, if unprotected, force water right through.
That’s why most reputable crews will walk you through a full plan, excavation, structural reinforcement, drainage systems, and moisture control, all in one package.
How It’s Done: Inside and Out
There are a few ways to do basement waterproofing properly during a lowering project:
Exterior Waterproofing (Best for Access)
If there’s enough room around your house, we’ll dig down, apply a waterproof membrane to the outside of the foundation walls, and install proper drainage like a weeping tile system. This keeps water out before it touches your walls.
Interior Waterproofing (When Space is Tight)
In tighter areas, think downtown semi-detached homes, we install an interior drainage system under the new floor. This routes any moisture into a sump pump system and safely out of the home.
Both approaches are incredibly effective when done alongside underpinning, because you’re already down there. It’s the best time to do it clean, right, and with minimal mess.
Think Long-Term, Not Just Livable Space
Let’s face it, most people are lowering their basement to make the space more useful. Maybe it’s an income suite, a rec room for the kids, or just finally having a ceiling you don’t hit your head on.
But if you only focus on square footage and headroom without thinking about moisture, you’re setting yourself up for future headaches. Because finished basements trap water. Insulation, drywall, flooring, these are all materials that don’t play nice with leaks.
By waterproofing during the dig, you’re not just building a better basement, you’re protecting your home from the ground up.
A Smart Time to Invest
Here’s something else to consider, waterproofing during a basement-lowering project doesn’t just save you future stress, it actually costs less overall. Why?
You already have excavation equipment on-site.
The crew is already down at the footings.
There are no finished surfaces to undo.
It’s one of those “while you’re at it” moments that actually makes financial sense.
If you’re already upgrading your foundation, extending the life of your home, and boosting property value, wouldn’t it make sense to protect that investment from water damage at the same time?
Planning a Project? Do It Once, Do It Right
If you’re thinking of lowering your basement floor in Toronto, don’t make the mistake of seeing waterproofing as a “next phase.” There’s no next phase when it comes to water damage, just emergency calls, insurance paperwork, and regrets.
It’s one job. It should be one plan.
So if you’re already planning to open up your basement, take the extra step. Include proper moisture control, even if the space isn’t being finished right away. Your future self, the one with dry floors, mold-free walls, and peace of mind, will thank you.
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We’ve helped hundreds of homeowners across Toronto tie foundation work with leak protection, from High Park to Greektown.
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