Exterior vs. Interior Waterproofing in Durham Region

Water in a basement can start quietly. A faint musty smell, a chalky white line on the wall, a damp corner after a storm. In Durham Region, clay soils, heavy rains, and spring thaws create real pressure against foundation walls. Choosing the right repair is not guesswork. At Wilworks Renovations, we diagnose the source, then recommend the method that stops the problem rather than hiding the symptom.

Durham Region has periods of saturation when soils hold water. That water builds hydrostatic pressure and pushes on the foundation. The easiest paths inside are vertical or step cracks, the seam where the wall meets the slab, cold joints, window wells, and weak exterior membranes. A dehumidifier helps with humidity but not with active water entry. The correct repair depends on how and where the water is getting in.

Our assessment begins outside. We check grading, downspout discharge distance, driveway edges that slope toward the house, and the condition of window wells. Inside, we map staining and efflorescence, test any sump system, and look closely at the wall to slab joint. We follow the evidence to the source, then match the fix to the cause. Only after this walkthrough do we recommend exterior or interior work.

Exterior work creates a continuous barrier and improves drainage before water meets the wall. After careful excavation to the footing, we clean the foundation, repair cracks, apply a waterproofing membrane, add drainage board, and verify or replace the footing drain. Backfill is done with proper stone and soil, and grading is set to shed water away from the home.

Best uses

• Membrane failure or obvious wall defects from the outside

• Poor grading or downspout placement that sends surface water to the foundation

• Window well leaks that require exterior rebuilds

What to consider

• • Excavation requires exterior access and protection of landscaping and hardscape

  • Weather can influence timing

  • The result is a source-level fix that protects the wall for the long term

Interior systems manage water that has reached the inside or is rising under the slab. We cut a narrow trench along the slab perimeter, install a perforated drain with filter stone, line the wall with a membrane to guide seepage down, and tie everything into a sump pit with a reliable pump and check valve. The system relieves hydrostatic pressure and gives water a controlled path out of the house.

Best uses

• Persistent seepage at the wall to floor joint

• Under-slab pressure that shows as damp or wet lines along the perimeter

• Situations where exterior access is limited or landscaping should be preserved

What to consider

• Interior work does not correct exterior grading or downspout issues

• A dependable sump is essential, and a battery backup is strongly recommended

• Visible wall cracks plus poor grading: exterior repair with grading and downspout corrections

• Seepage at the wall to floor joint or up through the slab: interior perimeter drain to relieve pressure

• Window well leaks: exterior, since the well and its drainage need rebuilding

• Limited exterior access or mature landscaping that should remain: interior, as long as the diagnosis supports it

• Mixed symptoms: a hybrid plan can make sense, for example exterior crack repair on one wall and interior drain on the rest

In North Oshawa, recurring wet spots appeared each spring. Stain mapping identified two vertical cracks and a flat side yard grade that directed runoff at the wall. We excavated and repaired the cracks, applied a membrane with drainage board, restored the drain, and corrected the grading. The problem did not return. Read the walkthrough here: North Oshawa Basement Waterproofing.

Even with exterior work, extreme weather can exceed normal drainage. A properly sized sump with a separate battery backup pump gives redundancy when power drops during storms. We test both pumps at handover and show you how to check operation in minutes.

• Assessment and plan. We identify the source, explain the method, and outline what areas will be touched.

• Protection. We protect finishes, mechanicals, and landscaping where needed.

• Execution. Exterior work includes excavation, crack repair, membrane, drainage board, and backfill. Interior work includes trenching, drain installation, sump tie-in, and concrete restoration.

• Verification. We test drainage, verify pump operation, and explain maintenance.

• Finish-ready wrap-up. If you plan to renovate the basement, we coordinate details so framing, flooring, and ventilation do not create new moisture traps.

Once water is controlled, you can safely plan living space. We help with moisture-smart materials and ventilation so comfort lasts. See our Basement Renovations for ideas and next steps.