Do I need weeping tile around a new addition foundation in Ottawa?

In most cases, yes. A new addition foundation, especially one with a basement or other below-grade space, needs a way to carry groundwater away from the footings, and a perimeter drain is the usual way to do it. Your designer will show the foundation drainage on the drawings to meet the Building Code for your site, and the City checks it before backfill. Ottawa's clay soils make good drainage especially worthwhile, because clay drains slowly and water that reaches the foundation from rain, snowmelt or groundwater needs a deliberate path away.

Weeping tile, also called a perimeter drain or footing drain, is perforated pipe laid along the base of the footing that collects water and carries it to a discharge point. A typical installation sets the pipe in a bed of clear crushed stone, covers it with more stone, and wraps the stone in filter fabric so fine soil particles don't clog the system over time. Fine clay is exactly what clogs an unprotected drain, so ask each contractor how they protect theirs.

The drain has to discharge somewhere approved, usually a sump pit with a pump or, where the City allows it, a storm connection. Your designer and the City will confirm what's acceptable at your address. If you'll rely on a sump, a pump with a battery backup is worth considering, since outages during storms are exactly when water arrives.

For an addition, the new drain either ties into the existing house's system or gets its own discharge point. If the house already has a sump, the new tile can often connect to it, though the pump may need more capacity. In an older home, the original drainage may be partly blocked, and tying new pipe into a failed system gives false security. A camera inspection or a separate sump for the addition can be the safer route; ask your contractor which they recommend and why.

Costs depend on the perimeter length, depth, soil and discharge arrangement, so ask for the drainage system as its own itemized line in each quote.

The detail most often missed is the junction between the old and new foundations. Water likes to travel along that joint, so the drainage needs to work right at that transition. Ask your contractor to detail it on the drawings and photograph it before backfill, for your records and the inspection.

To compare contractors who build foundations for additions, browse the Ottawa Construction Network directory and get itemized quotes.

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Looking for experienced contractors? The Ottawa Construction Network connects homeowners with qualified professionals:

• Homeupgraders
• RenoMotion Inc.
• Floor-2-Wall Inc
• Dreamwood Construction & Renovations
• Geerts Roofing Inc