Maintenance and Repairs

November 12, 2025 Published by Golden Horseshoe Chapter - By Allan Au-Duong

The Slippery Slope of Poor Waterproofing: Protecting Wood-Framed Balconies

From the Volume 25, Fall 2025 issue of the CCI GHC Condo News Magazine

With the changes in the Ontario Building Code allowing taller wood framed buildings, we are seeing more wood framed mid-rise condominium buildings in the market today.

With the changes in the Ontario Building Code allowing taller wood framed buildings, we are seeing more wood framed mid-rise condominium buildings in the market today. Due to Ontario’s demanding climate, safeguarding wood-framed buildings and balconies from water ingress is essential for maintaining structural integrity, occupant safety, and long-term durability. Single-ply waterproofing membranes such as PVC (polyvinyl chloride) have become an industry standard for balcony applications and provide durability and performance, if installed correctly.

Main field of balcony has bubbling and rippling.

Applications and Advantages of Single Ply Waterproofing Membranes

Balconies on wood-framed buildings must do more than just repel water - they must also serve as safe, durable walking surfaces for residents, and as a result, material options are limited. Single ply membranes provide a seamless, monolithic barrier that effectively prevents water penetration while offering flexibility and UV resistance. They are lightweight, adaptable to various substrate conditions, and suitable for retrofit and new-build applications.

Installation Keys to Success

When installed on wood-framed buildings, these membranes serve as a vital moisture barrier. Proper application involves thorough surface preparation, solid adhesion, and detailed flashing at penetrations, edges, and transitions. A well-executed system directs water efficiently to drainage paths, preventing it from reaching the wooden structural elements below.

Common Deficiencies in Waterproofing Systems

Despite their advantages, improper installation can result in significant deficiencies, including:

• Inadequate Surface Preparation: Failing to clean, dry, and smooth the substrate can impair adhesion, leading to bubbles, delamination, or premature failure.

Poor adhesion and bubbling at upturns.

• Poor Detailing and Flashing: Insufficient sealing around columns, railing post bases and lack of proper flashing or poorly adhered laps can create water entry points. Further, manufacturer compatible sealants must be used at penetrations.

Poor detailing at column bases.

Poor adhesion at balcony edge and penetrations not sealed.

• Edge and Termination Failures: Incorrect sealing or securing at edges and terminations. Proper termination such as mechanical fasteners or termination bars can prevent wind uplift, water leaks, and structural damage.

Edge termination failure.

Upturn peeling away and no termination bar.

• Long-Term Risks and Damage to Wood Structures

Inadequate waterproofing, especially in new construction, can result in severe, hidden and long-lasting damage:

• Water Infiltration and Rot: Continuous exposure to moisture promotes wood rot, mold growth, and deterioration of framing members.
• Structural Integrity Concerns: Damaged wood components compromise the load-bearing capacity of the structure, risking sagging or failure.
• Increased Repair Costs: Hidden damage often becomes visible only after significant degradation has occurred, necessitating extensive repairs and replacements.
• Reduced Component Lifespan and Safety: Water leakage and rot damage will shorten the life of the substructure and pose health hazards.

Substructure beginning to show moisture damage.

Wood structure beginning to show moisture damage.

The Crucial Role of Proper Waterproofing and Maintenance

To ensure long-term performance, waterproofing systems must be installed meticulously according to manufacturer specifications and relevant building codes. Routine inspections and prompt repairs are essential to catch minor damages before they escalate.

Even with high-quality waterproofing systems, wear and tear can occur over time — especially in high-traffic areas or at critical points like seams, edges, and around posts or drains. Fortunately, one of the key benefits of single ply membranes is that localized repairs are often possible without replacing the entire surface. Small punctures, delaminated seams, or damaged flashing details can typically be patched by professional contractors through cut and patch heat-welding and/or chemically bonded to the existing membrane.

Surface preparation for patch repair.

Heat welding for patch repair.

The Importance of Performance Audits in New Construction

In Ontario, new residential buildings are subject to comprehensive quality assurance processes governed by TARION Warranty Corporation. These include mandatory performance audits intended to verify that building systems — including waterproofing — meet safety, durability, and code compliance standards.

Failure to meet these standards can lead to deficiencies, warranty disputes, and the need for costly repairs. Ensuring compliance from the start helps secure long-term building performance and reduces future risks.

Conclusion

Single ply waterproofing membranes like PVC provide reliable protection for wood-framed buildings and balconies appropriate for Ontario’s climate. However, their success depends on precise application, detailed installation, and routine inspections and ongoing maintenance.

With the absorptive nature of the wood substructure, any waterproofing deficiencies can have a greater structural detriment as leaks often do not become evident until far too late; by the time leaks are identified, rot has often occurred to the structural elements leading to big surprises.

Recognizing their critical role during new and existing buildings ensuring the longevity, safety, and integrity of the structure for decades to come.

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Allan Au-Duong P.Eng.

With 15 years of industry experience, Allan Au-Duong leads the capital planning team at Brown & Beattie Ltd. Allan manages projects from Reserve Fund Studies, Performance Audits and Building Conditions Assessments for all condominium building types.