Interior vs exterior waterproofing comes down to one choice: stop water at the outside face of the wall, or let it reach the wall and carry it away from the inside. Both can keep a basement dry. They fix different problems.
What Are Two Types of Waterproofing?
The two types are named for where the work happens.
- Exterior waterproofing. The soil is dug away from the foundation wall. The outside face is cleaned, a waterproof membrane or coating goes on, and new weeping tile is often laid at the footing to carry water off.
- Interior waterproofing. The work happens inside the basement. A channel is cut into the floor along the walls, a drain pipe goes in, and the water runs to a sump pit where a pump lifts it out. A dimple membrane on the wall often guides seepage down into that drain.
What Problem Does Each Method Fix?
Exterior waterproofing keeps water out of the wall itself. That matters when water is soaking through the concrete, the outside membrane has failed, or the old weeping tile outside is broken or clogged.
Interior waterproofing manages water that is already getting in. It handles seepage where the wall meets the floor, water that rises under the slab, and leaks along the base of the wall. The wall still gets wet, but the water goes to the sump instead of across the floor.
Can a Basement Be Waterproofed From the Inside?
Yes. Interior drainage with a sump is the inside method, and it fits when digging outside is hard, for example where a driveway, deck, or the house next door sits against the wall.
What the inside method does not do is seal the outside of the wall. If a single crack is the only leak, it can often be sealed on its own. See our foundation crack repair page for that.
Which Waterproofing Method Is Best?
Neither is best for every house. The right one depends on where the water comes from.
- Exterior tends to fit when water comes through the walls in many places, the outside membrane or weeping tile has failed, or the soil is already being dug up for other foundation work.
- Interior tends to fit when water enters at the floor joint or under the slab, outside access is blocked, or the basement is unfinished along the walls.
- Some basements need both, for example a new outside membrane on one wall and an inside drain where water rises through the floor.
Before choosing, check the simple causes first: downspouts that dump next to the wall, and soil that slopes toward the house.
What Type of Basement Waterproofing Is Best for Winnipeg Homes?
Winnipeg's clay soil swells when wet and shrinks when dry, which puts pressure on walls and the floor joint. The question is still where the water is getting in. Note when the leak shows up, where it appears, and whether it follows rain, melt, or neither. That tells you which method fits.
For what changes the price of each method, see our leaking basement repair cost guide.
Need Help With a Wet Basement?
Read our basement waterproofing service page or call (431) 445-7139.