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Wood Clapboard Siding Repair: Preserving a Traditional Exterior Material

Wood clapboard on older Ontario homes can often be repaired rather than replaced. Here's how to approach it.

Siding Installation and Repair

Wood clapboard siding is the traditional exterior cladding of Ontario homes built before the vinyl era. Many of these homes retain original siding that, with appropriate repair and maintenance, can continue to perform for decades.

Cracked or split boards can often be repaired rather than replaced. Clean the crack, apply exterior waterproof glue, clamp or nail flat, and fill any remaining gap with exterior-grade filler before priming and painting.

Material Selection Guide

Warped or cupped boards — common in older unpainted wood — can sometimes be forced flat by face-nailing at strategic points after the wood has been moistened. This technique requires some skill to avoid splitting.

Rotted sections require cut-and-patch repair or full board replacement. Epoxy wood repair systems are highly effective for limited rot at ends and edges. Extensive rot across the board width means replacement.

What the Installation Process Looks Like

Back-priming replacement boards before installation seals all surfaces including the back face and cut ends. Paint that penetrates from the back side is a major cause of premature failure in replacement boards that aren't back-primed.

Replacing wood clapboard with a matching profile is feasible from specialty millwork suppliers, historic salvage sources, or by custom milling. Matching original dimensions is important for appearance, particularly on heritage properties.

Comprehensive repainting every 7-10 years maintains wood clapboard. Proper preparation — cleaning, scraping loose paint, filling cracks, priming bare areas — is more important than paint quality in determining how long the next paint job lasts.