How do I replace a rotted garage door frame in Saint John NB before winter?

Replacing a rotted garage door frame before winter is critical in Saint John's Maritime climate, but this is structural work that requires professional help due to the load-bearing nature of garage door headers and NB's heavy snow loads. You'll want to get this done before sustained freezing temperatures arrive, typically by late November.

A rotted garage door frame in Saint John is usually the result of moisture infiltration from the Bay of Fundy's humid air, poor flashing details, or ice dam backup during NB's freeze-thaw cycles. The frame consists of the header beam spanning the opening (which carries roof loads), the side jambs, and the sill plate at the bottom. If any of these components are structurally compromised, the entire door opening can sag, preventing proper door operation and potentially causing the door to bind or fall from its tracks.

The header beam is the most critical component because it carries the weight of the roof structure above, plus NB's snow loads of 2.4-4.8 kPa depending on your exact location in Saint John. This beam is typically an LVL (laminated veneer lumber) or built-up lumber assembly sized for the span and loads. Replacing it requires temporarily supporting the roof structure with posts and beams while the new header is installed. This is not DIY work — improper temporary support can cause the roof to sag or collapse.

Side jambs and sill plates are easier to replace but still require careful attention to structural connections and weatherproofing. The side jambs connect to the wall framing and must maintain the door opening's square and plumb dimensions. The sill plate sits on the concrete slab and is often the first component to rot because it's exposed to moisture from snow melt and poor drainage around the garage.

For Saint John's climate conditions, the replacement frame should use pressure-treated lumber for any components within 6 inches of the concrete slab, and all connections should be made with galvanized or stainless steel fasteners to prevent corrosion from salt air. The header should be wrapped with a weather-resistive barrier, and proper flashing must be installed above the opening to direct water away from the frame. Ice and water shield membrane should extend at least 36 inches up the roof from the garage door opening to prevent ice dam infiltration.

Timing is crucial for this repair. The work involves removing the existing garage door, demolishing the rotted frame, installing temporary roof support, setting the new frame, and reinstalling or replacing the door. This leaves your garage completely open to weather during construction. In Saint John, you want this completed before December when sustained freezing makes concrete work difficult and increases the risk of pipes freezing in attached garages.

Material costs for a standard 8-foot or 16-foot garage door frame replacement run $500-$1,500 depending on the span and lumber requirements. A new LVL header for a 16-foot double door opening costs $300-$600. Labor for professional installation typically runs $2,000-$4,000 for a complete frame replacement, including temporary support, demolition, framing, and weatherproofing.

When to Hire a Professional

This is definitely professional work. Garage door headers are load-bearing structural components that must be properly sized for NB snow loads and correctly supported during installation. A structural failure could damage your roof, injure someone, or create liability issues with your insurance. Additionally, if your garage is attached to your house, the frame replacement may affect the fire separation assembly between the garage and living space, which has specific code requirements.

Find a contractor experienced with garage door frame replacement who understands Saint John's coastal moisture conditions and can complete the work before winter weather arrives. The New Brunswick Construction Network can help you find qualified general contractors and carpenters in the Saint John area who specialize in this type of structural repair work.