Balcony and terrace waterproofing failures are a major source of structural damage in Ontario condos and townhomes. Water infiltration through deck membranes accounts for millions in repair claims annually.
Signs of Waterproofing Failure
- Water stains on ceiling below balcony
- Efflorescence (white salt deposits) on concrete edges
- Cracked or bubbling deck membrane
- Soft spots underfoot on tiled terrace
- Rusting balcony railings at base (indicates persistent moisture)
- Ponding water on deck surface (improper slope)
OBC Slope Requirements
Ontario Building Code requires balcony and terrace surfaces to slope minimum 1:50 (2%) toward drains. Inadequate slope is the leading cause of membrane premature failure.
Waterproofing System Options
Traffic-Bearing Membrane (most common for balconies)
- Liquid-applied polyurethane: $15-$25/sq ft installed
- Sheet membrane (torch-on modified bitumen): $12-$20/sq ft
- Both require protection course and finish topping
Below-Tile Systems (for tiled terraces)
- Hot-applied rubberized asphalt: $18-$30/sq ft
- Shower-pan style CPE membrane under mortar bed
Full Balcony Restoration Costs
Small balcony (15 sq ft): $3,500-$8,000
Medium balcony (50 sq ft): $8,000-$18,000
Large terrace (200+ sq ft): $25,000-$60,000
Costs include membrane removal, concrete repair, new waterproofing, protection board, and finish surface.
Full technical guide and contractor checklist: https://telegra.ph/Ontario-Balcony-and-Terrace-Waterproofing-Guide-2026-Failures-Systems-and-Replacement-Costs-04-26