When a Oshawa basement leaks and excavating outside the foundation is not feasible, interior waterproofing is the answer. Oshawa Concrete installs interior drainage tile around the slab perimeter, ties it to a sump pit and pump, and seals the inside face of the wall, a different system to exterior foundation waterproofing. Every project starts with a free written estimate.
Exterior waterproofing is the textbook answer when you can get to the outside of the foundation. In an established Oshawa home with a finished landscape, a tight setback, an attached garage or a deck over the work zone, excavating the outside is often impractical or unaffordable. Interior waterproofing is the alternative that does what waterproofing has to do, namely keep the basement dry.
It works by giving the water somewhere to go before it reaches the slab. We cut a perimeter trench in the basement floor, install interior drainage tile, route it to a sump pit with a pump, and seal the bottom of the wall so groundwater drops into the tile instead of bleeding across the slab.
The wall behind that is allowed to dry inward, the basement stops getting wet, and the rest of the basement, the slab, any renovation work above it, becomes finishable again.
Recent work
How it works
How We Waterproof a Basement From Inside
Trace where water reaches the slab
We trace where water arrives at the slab perimeter, mark high points, measure depth of the existing slab, and confirm the sump location and discharge path before any concrete is cut.
Cut perimeter and trench
The basement floor is cut along the wall perimeter, a trench is excavated to the right depth, and any old drainage that has failed is removed so the new system goes into clean material.
Install tile and sump pit
New drainage tile is laid in the trench on stone, sloped to a new sump pit set at the engineered low point, the pump and discharge line are installed, and the system is tested with water.
Backfill, pour slab, seal
The trench is backfilled with stone, the slab is poured to bind the system back into the floor, and the bottom of the wall is sealed so the wall can dry inward without bleeding water across the new slab.
When inside is the only option
Interior Waterproofing Has a Specific Job
Interior waterproofing is not a substitute for fixing the foundation. If the wall itself is failing structurally or if there is a known specific exterior cause that can be reasonably reached, exterior foundation waterproofing is still the right tool.
Where interior waterproofing shines is in established homes with finished outsides and a recurring inside leak, and in basements where the goal is to get the slab dry enough to finish the renovation. The system is well-proven, the pump is the moving part you maintain, and the basement gets back to dry.
Drainage tile, sump pits, pumps and when interior is the right answer to a wet basement.
For its job, yes. The two systems do different work. Exterior keeps water from ever reaching the wall; interior accepts that water reaches the wall, intercepts it at the slab perimeter and pumps it out. When excavating outside is impractical, the interior system is the right one.
An interior system needs a sump pit and a pump to move collected water out. A battery backup pump is strongly recommended in Oshawa, where spring runoff and power outages can overlap. We size the pump and pit to the inflow we measure.
The perimeter has to be opened up, which means baseboards, lower drywall and any finished flooring against the wall come off in the work zone. We coordinate that carefully so the rest of the basement is undisturbed.
It will intercept the water at the slab so the floor stays dry, but a leaking wall crack itself is a separate fix; pair this with crack repair or, if the crack is structural, foundation crack repair from the engineered side.
A typical residential interior system takes about a week from cut to closed slab, depending on the perimeter length and how much of the basement has to be uncovered to reach the work. The full schedule is in the quote.
Homeowner reviews
What Oshawa Homeowners Say About Their Interior Waterproofing
We could not dig up the front of the house. Interior system put in, sump pit cut, dry basement two springs running. Honest about the system being the right tool here.
S. F.
Oshawa
★★★★★
Existing finished basement, leaks in three corners. They opened only what they had to, installed the tile and sump, closed it back up clean. The pump runs, basement is dry.
E. I.
Toronto
★★★★★
They explained why interior was the answer in our situation and not just upselling exterior. The system has worked through every melt since. Trust earned.
Q. P.
Brampton
★★★★★
Battery backup pump was their recommendation and we are glad we listened. Lost power for a day this spring; basement stayed dry the whole time. Worth every dollar.
X. B.
Mississauga
From the blog
Concrete Guides & Articles
Practical reading on planning, finishes and caring for concrete in Oshawa.
Tell us where the basement is wet, how often and what is finished around it, and we will visit free and put the right interior waterproofing system into a written quote.
