Exterior trim to siding
Sun, rain, and constant movement. Use an exterior-rated, paintable sealant with a real movement rating.
Our pick: OSI Quad Max, DAP Dynaflex Ultra, Soudal Fix ALL
Caulk by room
Windows & doors
Let it all hang out… then seal it up
A drafty window is basically just a polite hole in your wall. Window and door caulk needs to bond to multiple substrates (wood, aluminum, vinyl, brick), flex with temperature swings, and hold up for years without cracking. Polyurethane and elastomeric formulations are the go-tos for exterior applications; paintable acrylic for interior finishing.
Your guideZoe, windows, doors & drafts
Where to caulk in the windows & doors
Every joint in the room, what goes in it, and why. The color bar matches the formulation.
Frame to brick, stone or stucco
Masonry is rough and porous and the joint is often wide. Polyurethane or hybrid grips it; use backer rod when the gap is over 1/4 inch.
Our pick: Sikaflex-1a, Soudal Fix ALL
Interior casing to wall
Stops the draft you feel around the trim and cleans up the paint line.
Our pick: DAP Alex Plus
Door threshold and sill
Seal where the sill meets the jambs and the floor, keeping water from wicking under the door.
Our pick: GE Silicone 2 Kitchen & Bath, Sikaflex-1a
Glass to frame
Old wood sash takes glazing putty, not caulk. Clear silicone is fine on metal and vinyl stops.
Our pick: Sashco Lexel, Gorilla 100% Silicone
Weep holes and drainage gaps
Not a caulk job
The little slots at the bottom of vinyl and aluminum frames let water out. They are supposed to be open.
Never caulk weep holes.
Seal a drafty exterior window
Find the leaks
On a windy day, move a strip of tissue or a stick of incense slowly around the trim. Where it flutters, air is moving.
Cut out failed caulk
Anything cracked, hard, or pulling away comes out. New caulk on old caulk fails with it.
Clean and dry
Brush out dirt and cobwebs; wipe vinyl and metal with alcohol. Bare wood should be primed.
Backer rod for big gaps
Over about 1/4 inch wide or deep, press in foam backer rod first so the bead is the right depth.
Bead and tool
Work on a mild, dry day within the temperature range on the tube. Tool the bead into the joint.
Paint after the cure time
Most exterior sealants take paint once they've skinned or cured; the tube gives the window.
Mistakes we see
- Caulking weep holes shut.
- Painting a sash shut with caulk. The window has to open.
- Using interior caulk outside. UV and movement will crack it in a season.
- Filling deep gaps without backer rod, which leads to three-sided adhesion and torn beads.
- Caulking in freezing weather or right before rain.
How long it lasts
- Check it
- Each fall, before heating season.
- Redo when
- You see cracks, gaps, or feel a draft.
- Typical life
- Years with a good exterior sealant; the sunny side wears out first.
Windows & doors questions
Inside or outside?
Both, for different reasons. Outside keeps water out of the wall; inside stops air leaks you can feel.
What's rope caulk?
A removable putty cord you press into gaps for the winter and peel out in spring. Great for renters and windows that open.
Can I caulk vinyl windows?
Yes, with a sealant that lists vinyl as a substrate. Hybrids and many advanced latex sealants do; wipe the vinyl with alcohol first.
More answers in the full FAQ, or let the Caulk Finder pick for you.
