You’ll find dozens of types of caulk at your local home improvement store, and each type is intended for a specific situation.
Exterior windows: To stand up to the elements, exterior caulk should be impervious to harsh sun rays, water, and fluctuating temperatures. The tube of caulk should specify it’s intended for exterior surfaces; we like Sashco Big Stretch Caulk (available from Amazon).
Interior windows: The caulk used on interior windows should not emit toxic fumes and hold paint well. High-quality, paintable latex, such as White Lightning’s Painter’s Preferred Acrylic Latex Caulk (available from Amazon), is a good choice for interior windows.
Humid rooms: Caulking windows in a room with high humidity, such as a bathroom, calls for interior caulk that’s waterproof and mold-resistant. Kwik Seal Ultra (from The Home Depot) works well in steamy situations.
Masonry siding: When caulking seams between windows and masonry siding, including basement windows and windows on stucco or brick homes, you’ll need an exterior caulk that’s compatible with both the window and the masonry surface.
DON’T CAULK OVER OLD CAULK
If the existing caulk has hardened and is pulling away, running a bead over it is sure to be an exercise in futility. The old caulk will continue to pull away, taking the new caulk off with it
DO USE A CAULKING GUN WITH A THUMB RELEASE
Cheap caulking guns come with a ratchet-style handle that must be twisted loose to release the pressure on the caulk in the tube.
DON’T CUT TOO MUCH OFF THE END OF THE CAULK TUBE TIP
The plastic tip on a caulk tube narrows to a point, and the more you cut off, the larger the bead of caulk will be.
Doors & Windows
DO USE BOTH HANDS TO RUN THE BEAD
It takes two hands to control a caulking gun. Use your dominant hand to hold the gun, pull the trigger, and support the gun's barrel near the tip with your other hand.
DON’T RUN A CONTINUOUS BEAD FROM THE TOP TO THE BOTTOM OR FROM ONE SIDE TO THE OTHER
By the time you reach the end of the bead, you’ll have to change your grip on the caulk gun, which will affect the uniformity of the bead