Increased risk of infiltration after replacing doors and windows: what every homeowner should know

When you replace your home's doors and windows, you expect to improve the comfort, energy efficiency, and aesthetics of your home. However, one often-overlooked technical detail can increase the risk of water infiltration and cause costly damage: a broken weather barrier membrane.

1. The essential role of the weatherproof membrane

The weather barrier membrane (often called a "weather-resistant barrier" or "WRB") is the first line of defense against water and air trying to penetrate the building envelope. It must form a continuous system around the house, sealed at all openings, to redirect water to the outside.

When removing old doors and windows, this membrane is cut, torn off, or displaced , creating discontinuities. If it is not restored properly when installing the new units, rainwater can seep behind the siding, make its way into the structure, and cause:

• Timber rot

• Detachment or swelling of interior gypsum

• Mold growth and poor air quality

  
  

2. Critical points around openings

The corners of openings are particularly vulnerable. A simple unsealed gap or a poorly executed overlap between the flashing, membrane, and window frame can create a direct entry point for water. The more careful the installation—with self-adhesive flashing, sealants, and a properly connected membrane—the more durable the installation.

3. The importance of a professional connection

A replacement carried out without completely restoring the waterproofing is tantamount to leaving "invisible entry points" for water. A conscientious installer:

• Inspects the continuity of the weather shield

• Restore the membrane around the frame before installing the new door or window

• Seals flashings and junctions to direct water outwards

  
  

4. Conclusion and recommendation

Replacing your doors and windows is a significant investment. To ensure long-term protection for your home, insist that the contractor restores the building's waterproofing according to best practices and the requirements of the Quebec Construction Code (section 9.27 on waterproofing). A simple oversight can turn into a major leak problem a few years later.