Dealt with a balcony waterproofing failure on my Toronto semi-detached last year. The repair ended up being more involved than expected - posting the details for anyone who spots similar warning signs.
What Tipped Me Off
Water staining appeared on the living room ceiling directly below the second-floor balcony after the spring thaw. I had noticed the vinyl membrane on the balcony was bubbling at the edges for about a year and ignored it. That was a mistake.
What Was Found
When the contractor pulled back the failing vinyl membrane (Duradek-type system, probably 15 years old):
- Plywood subdecking was saturated and delaminated at the outer 12 inches
- One joist end was soft with early rot
- The drip edge flashing had separated from the wall
Scope of Repair
- Remove failed membrane
- Replace outer 16" of subdecking (2 sheets partial)
- Treat exposed joists with borates, sistered the soft joist
- Install new drip edge and wall flashing integration
- Install new Duradek vinyl membrane
- New aluminum trim at perimeter
Cost: $6,400
That balcony is roughly 160 sq ft. Cost would have been $3,500-$4,000 if I had not let the subdecking rot. Lesson: fix bubbling membrane immediately.
Warning Signs to Watch For
- Bubbling or lifting at membrane seams or edges
- Cracking or chalking of membrane surface
- Water staining on ceilings below
- Soft spots when walking on the deck
- Visible separation at wall-to-deck transitions
Anyone else navigating a balcony membrane replacement? Particularly curious if anyone has compared Duradek vs fiberglass (FRP) for residential applications.