Brick window sills spend years catching rain, melting snow, and runoff from the glass above them. Most homeowners rarely pay much attention to these small sections of masonry until something begins to look wrong.
A mortar joint opens.One of the sill bricks tilts. Dark staining begins appearing beneath the window.
Because the affected area is small compared with the rest of the wall, it can be tempting to leave the repair for another season.
Window sills deserve more attention than their size suggests. Their job includes directing water away from an opening in the wall. Once the masonry begins holding water or allowing it behind the brick, damage can spread beyond the sill itself.
A Masonry Sill Needs To Shed Water
A properly built sill slopes outward so rainwater moves away from the window instead of settling against it.
That slope may seem minor, but it becomes important every time the wall gets wet. Flat areas allow water to linger. A sill that has shifted toward the building can direct moisture back toward the window opening.
Older brick sills can change position as mortar deteriorates or individual bricks loosen. Freeze and thaw cycles can make the movement worse once moisture begins entering small cracks.
If water repeatedly remains in the same area, the surrounding masonry has less opportunity to dry between storms.
Mortar Joints Often Show Trouble First
The joints between sill bricks are exposed to a difficult combination of water and weather.
Small cracks may begin forming where the mortar meets the brick. Once those cracks open, water has an easier path into the sill assembly.
Simply spreading new mortar over the surface usually does not provide a lasting repair. Loose material needs to be removed so replacement mortar can bond properly. The condition of the bricks also needs to be checked before the joint is rebuilt.
If a brick has already begun breaking apart, repairing only the mortar leaves damaged material in place.
Watch The Area Below The Window
A failing sill does not always announce itself with a large crack.
Look at the brick directly beneath the window. White mineral deposits can suggest that moisture is moving through the masonry. Dark areas that remain wet longer than the surrounding wall deserve attention as well.
Interior clues may appear too. Moisture around the window opening can sometimes be mistaken for a problem with the window itself when the surrounding masonry is contributing to the leak.
Finding the source matters because sealing the inside does little good if water continues entering through damaged masonry outside.
Flashing Helps Manage Water Behind The Brick
Exterior brick is designed to deal with weather, but some moisture can still move through masonry assemblies. Proper construction provides a way for that moisture to leave.
Around window sills, flashing can help direct water toward the exterior. Weep openings allow moisture within the wall cavity to drain rather than remaining trapped behind the veneer.
Problems develop when flashing is missing or damaged. Blocked drainage can create similar trouble.
Repairing the visible sill without considering what is happening behind it may improve the appearance while leaving the moisture problem unchanged.
Michigan Winters Can Accelerate Sill Damage
Water inside masonry becomes especially troublesome once temperatures begin crossing the freezing point.
Moisture expands as it freezes. Repeated cycles place stress on brick surfaces and mortar joints. A small opening in fall can become much more noticeable after a Michigan winter.
This is one reason cracked sill joints are worth addressing before cold weather arrives. Keeping unnecessary water out of the masonry reduces the amount available to freeze inside it.
Bricks that have already begun flaking or losing their outer face may eventually need replacement.
Caulk Cannot Fix Every Sill Problem
Sealant has an important role where masonry meets certain window components, but it should not be used to cover deteriorated brickwork.
A bead of caulk across cracked mortar can hide the opening temporarily without restoring the joint underneath. Applying sealant in the wrong location may also interfere with drainage.
The repair should match the source of the problem. Failed mortar calls for masonry work. Loose sill bricks need to be reset or replaced. Drainage issues require attention to the way water moves through the wall.
Covering everything with sealant can make future diagnosis harder.
Restore Damaged Brickwork with Professional Masonry Services
Window sill problems are often easier to address while the damage remains concentrated around the opening.
Once water begins affecting a larger section of wall, repairs can involve much more than a few joints or damaged bricks. Early work can restore the sill’s ability to shed water while protecting the masonry beneath it.
Primo Contracting provides masonry construction and repair services throughout Rochester Hills and surrounding Michigan communities. From repairing deteriorated mortar joints and replacing damaged bricks to restoring brickwork, rebuilding masonry structures, and completing new masonry installations, we deliver quality workmanship designed to withstand Michigan’s changing seasons.
Noticing cracks, shifting bricks, or moisture stains around your windows? Contact us for a Free estimate today!