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Window Sill Repair & Replacement - From Water Damage to Rotted Window Sills
Window sills may frame your view, but they are actually part of the wall itself—your home’s first line of defence against water infiltration. A properly designed sill channels rain and meltwater away from the façade, keeping the masonry below dry and sound. When a sill deteriorates, that protection disappears, inviting moisture damage and costly repairs.
At Cornerstone Brickworks, window sill replacement is one of our signature services. Whether you need a repoint, a full replacement, or a brand‑new installation, our craftsmen match materials, colour, and profile to preserve your home’s character while boosting its durability. Using time‑tested techniques and high‑performance stone or man-made sills, we create windows that shed water cleanly, enhance curb appeal, and stand up to Canada’s toughest weather—year after year. Every project is unique, and we treat it that way, delivering workmanship you can trust to protect your investment for decades.
Types of Buildings We Work On
Window Sills play a small but decisive role in a wall’s defence system: when they fail, water finds its way behind the façade, accelerating mortar erosion, staining brickwork, and undermining structural integrity. At Cornerstone Brickworks, we replace and restore sills on homes of every vintage, matching original materials and profiles to keep each building watertight and true to its character.
- Modern construction often relies on brick sills set in mortar and — crucially — lacks a drip edge. Over time these joints degrade, and the flat surface channels water straight into the wall cavity or surrounding masonry. We recommend replacing these sills with a single piece or man-made unit, with a proper slope and cut‑in drip edge. This gives the masonry the drainage & protection it has always needed.
- Heritage homes usually feature limestone or sandstone sills complete with a drip edge. These stones are as much a part of the home’s charm as its weatherproofing, so we source or mill matching natural stone and set it in sympathetic lime‑rich mortar to honour traditional craftsmanship.
Whichever era your home belongs to, our tailored approach ensures your new window sills shed water cleanly, preserve the surrounding masonry, and look as though they have always belonged.
Water - The Enemy of Window Sills
When moisture slips in behind a deteriorating window sill, the consequences multiply quickly: timber frames rot, bricks spall, and the wall loses its first and strongest layer of defence. Left unchecked, these hidden failures compromise the entire facade and lead to expensive, invasive repairs. Proactive sill maintenance—or timely replacement—keeps water exactly where it belongs, safeguarding your masonry, window frames, and budget for years to come.
Causes of Window Sill Damage
Brick window sills may be budget‑friendly for builders, but their porous surface behaves more like a sponge than a shield—soaking up rain, lacking a drip edge, and eventually funneling moisture into the masonry below. Replacing those bricks with a single piece of natural stone transforms the sill into a lifelong umbrella, directing water clear of the wall and resisting freeze–thaw damage.
Concrete sills can fail just as dramatically, but from the inside out: when reinforcing steel isn’t fully protected, moisture reaches the rebar, rust causes it to swell, and the expanding steel cracks the concrete. Those fissures invite even more water, accelerating deterioration. Our team removes compromised material and installs properly reinforced, water‑repellent stone or concrete sills, restoring both strength and a clean runoff path—so your home stays protected, season after season.
Maintenance of Window Sills
Window sills sit on the front line of every storm, taking the brunt of rain, meltwater, and freeze‑thaw cycles. Periodic repointing with the right mortar seals hairline gaps before they become gateways for moisture, sparing you the high cost of full sill replacements later. When water seeps in behind a worn joint, it can trigger damage to the surrounding masonry, rotting of structural wood, and even sill failure—repairs that quickly snowball in scope and price. To add an extra layer of defence, we install a waterproof starter strip (soft flashing) beneath every sill and incorporate discreet weep vents that let any incidental moisture drain safely away. This belt‑and‑suspenders approach keeps water out, prevents hidden rot and mould, and preserves the masonry—protecting your home’s value for years to come.
Masonry for Arches and Lintels
Arches and lintels carry the load above windows, doors, and other openings—but years of settling, moisture, and freeze‑thaw cycles can leave them cracked, bowed, or out of alignment, jeopardizing the wall above. At Cornerstone Brickworks, we stabilize these vital supports by carefully dismantling the compromised area, installing a concealed galvanized angle‑iron lintel for added strength, and rebuilding the opening in materials that match the original. The result is a structurally sound, visually seamless repair that protects your home and preserves its character for decades to come
Our Repair Guarantee for Window Sills
Every sill we install is precision‑sloped to channel water safely away from the façade, eliminating pooling and keeping runoff off your masonry. Beneath each sill we add a waterproof starter strip (soft flashing) and set discreet weep vents, giving any incidental moisture a clear path to drain and adding a second line of defence against water intrusion.
We build with premium materials—natural stone, high‑density concrete, and engineered stone—selected for strength, weather resistance, and a perfect aesthetic match to your home. Whenever possible, we craft sills in the largest practical sections to minimise mortar joints and potential weak points. The result is a clean, durable installation backed by our five‑year workmanship warranty, so you can trust your window sills to perform flawlessly while safeguarding your investment for decades.
See Our Work: Before and After Photos
