Caulking & weatherproofing: where to seal, what product to use, and 5-year longevity

Most caulk failures come from using the wrong product. Three chemistries cover ~95% of residential needs: (1) 100% silicone — the kitchen/bath/glass standard. Won't mildew (with mildew-resistant variant), bonds to porcelain + glass + tile. NOT paintable. NOT for exterior trim that will be painted. ~$8-$15/tube, 25+ year lifespan. (2) Polyurethane — exterior workhorse. Bonds to wood, brick, concrete, vinyl. Paintable after 24 hours. Tough but tougher to tool (sticks to fingers + tools). ~$8-$12/tube, 20+ year lifespan. The right call for most exterior trim joints, masonry-to-frame transitions, vinyl-to-brick. (3) Acrylic latex (with silicone, e.g., DAP Alex Plus) — interior trim, baseboards, crown moulding. Easy to tool, paintable in 30 minutes. Cheap. NOT for wet areas. ~$3-$5/tube, 5-10 year lifespan. There's also butyl (specialty roof + flashing work), polysulfide (windows, very long-life), and modified silicone (a newer paintable hybrid).

Top-priority sealing locations, ordered by dollars-saved-per-tube: (1) Around windows + exterior doors — frame-to-siding gap, every gap. Polyurethane outside, silicone-acrylic hybrid inside. ~$50-$150 in materials, $300-$600 in labor for whole house. (2) Bathroom — tub-to-tile, tile-to-floor, sink-to-counter, around toilet base. 100% silicone with mildew-resistant rating. (3) Kitchen — sink rim, counter-to-backsplash, dishwasher gap. 100% silicone food-safe. (4) Exterior trim — soffit-to-siding, vertical trim joints. Polyurethane. (5) Crown moulding + baseboard gaps — interior cosmetic + small drafts. Acrylic latex. (6) Foundation crack hairlines — polyurethane or specialty concrete sealant.

A $4 tube of acrylic latex on a clean, dry, properly-cut joint outlasts an $18 tube of silicone slapped onto a dirty wet joint. The prep that matters: (1) Remove old caulk completely — a knife + caulk-remover gel ($8-$15). Don't caulk over old caulk; the new caulk bonds to the old, and when the old fails, the new comes off with it. (2) Clean the joint — denatured alcohol or rubbing alcohol on a rag for kitchen/bath; mineral spirits for exterior trim. Let dry fully. (3) Tape the joint edges — painter's tape gives sharp lines + protects adjacent surfaces. (4) Use a backer rod for joints wider than ~1/4" — closed-cell foam rope inserted before caulking; lets the caulk move with the joint instead of cracking. ~$5 for 25 ft. Skip backer rod on a wide joint and the caulk fails in a year.

Pro tooling separates good caulk from bad. (1) Cut the tube tip at a 45° angle, smaller hole than the joint — better to start small + cut wider. (2) Apply continuous bead, no stopping mid-joint (creates failure points). Move steadily — a typical joint takes 8-12 seconds for a 4-foot run. (3) Tool the bead within 5 minutes (silicone) / 2 minutes (latex). A wet finger works for latex; a soapy water spray + finger or specialty tool for silicone (it sticks to dry fingers). (4) Pull tape while caulk is still tacky — peeling later tears the bead edge. (5) Don't paint over silicone — paint won't stick. If you need paintable, use polyurethane or modified silicone, not 100% silicone.

Caulk seals static joints; weatherstripping seals moving ones (doors, windows that open, attic hatches). Three types: (1) V-strip (tension seal) — adhesive-backed plastic V profile; sticks to door/window frame; compresses when closed. $4-$8 per door. The standard for most operating doors. (2) Foam tape — open-cell foam adhesive strip; cheap ($3-$6/roll); compresses well; lifespan 2-5 years. Best for attic hatches and infrequent-use doors. (3) Door sweep — strip with bristle/rubber that closes the gap at the bottom of the door. $10-$25 per door. Critical for exterior doors. Annual maintenance: replace any compressed/torn weatherstripping; check the door sweep for daylight. ~$50/year in materials catches most of the typical home's air leaks at the operating-door perimeter.

DIY-friendly: kitchen + bathroom caulking, weatherstripping, interior trim. Worth hiring out: whole-house exterior caulking (involves ladder work + a lot of joint footage), high windows, foundation cracks (need diagnosis vs cosmetic seal), specialty work like polysulfide on aluminum windows. A pro caulking pass for a typical 2,000 sq ft house exterior is $400-$1,000, materials included; usually 1-2 days of work.