Window caulking and draft sealing

Why fall is the time

Caulk takes a beating over a valley summer. Months of sun and heat dry it out, and the stucco and window frames expand and shrink every day. By October, the caulk around many windows has cracked, pulled away at the corners or turned chalky.

Fall brings the first cool nights and the Santa Ana wind season, when every gap whistles and fine dust blows in. Resealing before then means a warmer, cleaner house for the winter, and caulk cures well in mild fall temperatures.

Where we look

• The joint where the window frame meets the stucco outside.
• The top of the window frame, where water runs down the wall.
• The interior joint between the frame and the drywall or trim.
• Window sills and the corners where sill meets frame.
• Pipes, cables, vents and hose bibs that pass through walls.
• The joints around door frames and the garage side door.

Sliding windows also lose air through worn pile strips in the sash. That is weatherstripping rather than caulk; see weatherstripping and door sweeps.

Outside first

Exterior caulk keeps rain out of the wall as well as wind. We cut out the old bead, scrape off loose material, clean dust and chalk from the joint, and let it dry. Then we lay a new bead of exterior-grade sealant that stays flexible as the stucco and frame move.

Polyurethane and hybrid sealants grip stucco well and can be painted; silicone sheds water but will not hold paint. We pick by whether the joint will be painted.

One important detail: at the bottom of many windows, small weep holes or gaps let water that gets into the frame drain out. Those must stay open. Sealing them traps water in the frame. We leave weeps clear on purpose.

Inside joints

Inside, gaps between the window frame and the drywall or trim let air move between the wall cavity and the room. A thin bead of paintable acrylic caulk closes them. Where the gap is wider than a pencil, a foam backer rod goes in first so the caulk is the right depth. We tool every bead smooth and wipe excess so it looks neat, then it can be painted to match.

Testing for drafts

On a windy evening, hold a lit incense stick near window corners, outlets on exterior walls and around pipes under sinks. Where the smoke flutters, air is moving. Mark the spots with tape and include a photo in your text. That list tells us where to spend time.

What sealing does and does not do

Sealing gaps helps comfort and keeps dust and bugs out. It does not turn a single-pane window into an insulated one; heat still passes through the glass. If windows are failing in other ways, such as broken sashes, fogged dual panes or rotted frames, see window replacement and wood rot repair.

Ladders and second floors

Ground-floor windows are done from the ground or a step ladder. Second-floor windows are done from an extension ladder set on firm, level ground, or from inside where the window allows. We do not work from roofs or ledges. Windows that cannot be reached safely that way are noted for you rather than forced.

A whole-house visit

A full reseal covers every window outside, the leakiest ones inside, and the pipe and vent penetrations; how long it takes depends on the house, and we’ll tell you after seeing photos. We note any rot, cracked stucco or failed glass we see along the way and send you photos, so you know what else needs attention before the rains.

Photos for the quote

A photo of a typical window outside, close enough to see the caulk, plus a count of windows, is enough for a price.

Weather for caulking

Most sealants want a dry joint and mild temperatures to cure well. We avoid caulking right before rain and in the heat of a summer afternoon on a sun-baked wall, when beads skin over too fast. Fall mornings are ideal.

Choosing the sealant

Sealant tubes make big promises. What matters is whether the product is rated for exterior use, how much movement it handles, and whether it can be painted. On stucco next to aluminum frames, we favor a paintable hybrid sealant that bonds to both.

Inside, a paintable acrylic latex with silicone handles small gaps well. Clear silicone is for spots that will never be painted, such as glass to metal.

Color and paint

White and clear sealants are common, but bronze, gray and beige versions blend better with many frames and walls. When the stucco is painted, we can paint over a paintable bead after it cures, so the joint disappears.

Rental units

Owners of rentals often ask for a yearly reseal between tenants. Fresh caulk around windows and tubs makes a unit look cared for and catches small leaks early. We send photos of each window before and after for your records.