Caulk Types Compared: Which Caulk for Which Job

Quick answer

Wet, unpainted joints (tubs, showers, sinks): 100% silicone. Paintable interior trim and drywall gaps: acrylic latex. Exterior joints that move (siding, window frames, trim): polyurethane. Kitchen and bath that must stay flexible: silicone or siliconised latex with mildew resistance. Picking the wrong type is the #1 reason caulk fails early.

The caulk aisle is deliberately confusing: dozens of tubes, overlapping claims, and fine print that matters. But nearly every homeowner job comes down to four chemistries. Learn what each one does, and choosing takes thirty seconds instead of thirty minutes.

The four types at a glance

Match the caulk to the job

Kitchen and bathroom. Water wins here, so water resistance rules. Use 100% silicone around tubs, showers, and sinks — ideally a kitchen-and-bath formula with mildew resistance. It tools smoothly, lasts a decade or more, and peels out cleanly when it finally needs replacing. The trade-off: you cannot paint it, so keep it off trim.

Interior trim and walls. Baseboards, crown moulding, window casing, and drywall corners all get painted, so acrylic latex is the workhorse. It is cheap, water-cleanup, tools with a damp finger, and takes paint within the hour. It is not flexible enough for exterior movement — keep it indoors.

Windows and doors (exterior). These joints expand and contract with temperature all year. Polyurethane is the pro choice: it bonds to almost everything, stays flexible for years, and accepts paint. It is fussier to apply and needs solvent cleanup, which is why homeowners often reach for latex — and then recaulk in two years.

Concrete and masonry. Movement plus alkalinity kills ordinary latex. Polyurethane or a dedicated concrete/masonry sealant handles the expansion joints in driveways, steps, and foundation walls. For wide gaps, press in foam backer rod first so the caulk bonds to two sides instead of three — a three-sided bond tears itself apart.

Roofing and gutters. Butyl rubber or elastomeric sealants stay pliable through extreme temperature swings and stick to metal. Standard latex fails fast up here.

What you need

Tools needed

• Caulk gun (smooth-rod, midrange — avoid the cheapest stamped models)
• Utility knife
• Painter's tape
• Damp rags and a cup of water
• Optional: caulk removal tool for old silicone

Materials needed

• Correct caulk tube for your joint (see matrix above)
• Foam backer rod for gaps wider than 6mm
• Rubbing alcohol for surface prep
• Mineral spirits (only if using silicone or polyurethane)
• Disposable gloves

Apply it properly

Step-by-step instructions

1. 1

   Identify the joint

   Note whether the joint is wet or dry, interior or exterior, and whether it will be painted. Wet areas need silicone; paintable trim needs latex; exterior joints that move need polyurethane.

2. 2

   Pick the caulk type from the matrix

   Use the comparison table above to match your joint to silicone, latex, polyurethane, or a hybrid. When in doubt, buy the paintable option only if you plan to paint.

3. 3

   Remove old caulk and clean the joint

   Cut out failed caulk with a utility knife or removal tool, then clean the joint with rubbing alcohol or soapy water and let it dry fully. New caulk bonds poorly to old residue.

4. 4

   Cut the tip and load the gun

   Cut the nozzle at 45 degrees, sizing the opening slightly smaller than the joint. Puncture the inner seal, load the tube, and squeeze a test bead on cardboard.

5. 5

   Apply a steady bead

   Hold the gun at 45 degrees and move at an even pace so the bead fills the joint without gaps. Keep gentle, constant pressure rather than stopping and starting.

6. 6

   Tool the bead and remove tape

   Smooth the bead with a wet finger (latex) or a gloved finger (silicone), then pull painter's tape immediately while the caulk is still wet for crisp lines.

7. 7

   Let it cure before painting or wetting

   Latex can often be painted within the hour; silicone needs 24 hours to cure and generally cannot be painted. Check the tube — rushing this step ruins the finish.

The two-tube rule for autumn

If you only stock two tubes, make them premium acrylic latex (interior trim, painted surfaces) and polyurethane (exterior joints). Between them they cover nearly every joint in the house. Add a tube of kitchen-and-bath silicone when the bathroom needs attention — see our recaulking guide for the full technique — and work both into your fall weatherization routine alongside draft-proofing your doors. Sealing air leaks before heating season is one of the cheapest energy upgrades there is.