Overview

This task covers removing old, cracked exterior or interior caulk around window and door frames and applying a fresh weatherproof bead to stop drafts, water intrusion, and energy loss. It suits a homeowner tackling seasonal maintenance (often before winter or after noticing a draft) or someone patching gaps left after a new window or door install. It's approachable with basic tools, though second-story or hard-to-reach windows add a ladder-safety element.

Tools & materials

  • Exterior-grade sealant such as polyurethane or high-quality silicone caulk for outdoor window/door trim (durable, weatherproof, paintable polyurethane is easiest if you plan to paint over it — plain silicone resists water best but won't take paint)
  • Siliconized acrylic latex ("painter's caulk") for interior trim and gaps, since it's paintable and cleans up with water
  • Caulking gun (a smooth-rod or dripless model is easier to control)
  • Utility knife or a dedicated caulk-removal tool
  • Putty knife
  • Foam backer rod, for any gap wider than about 1/4 inch
  • Rubbing alcohol or mineral spirits and clean rags
  • Painter's tape
  • Small cup of water or a caulk-smoothing tool
  • Ladder, if working on upper-story windows

Steps

  1. Inspect the frame for cracked, dried-out, or missing caulk and note any gaps wider than a pencil, which will need backer rod first.
  2. Scrape and cut away all old caulk with a putty knife and utility knife, working it loose in sections rather than trying to pull one long strip.
  3. Clean the joint with rubbing alcohol or mineral spirits and let it dry fully — caulk won't bond to a dusty, damp, or peeling surface.
  4. For gaps deeper or wider than about 1/4 inch, press foam backer rod into the gap first so the caulk only has to bridge the surface, not fill the whole cavity.
  5. Apply painter's tape along both sides of the seam if you want crisp lines, especially on trim you plan to paint.
  6. Cut the caulk tube tip at a 45-degree angle to match the gap width and load it into the gun.
  7. Holding the gun at a steady 45-degree angle, run a smooth, continuous bead along the full length of the gap, working corner to center rather than stopping partway.
  8. Smooth the bead promptly with a wet finger or smoothing tool in short sections, rather than trying to drag the whole length at once.
  9. Remove the painter's tape immediately while the caulk is still wet.
  10. Let the caulk cure per the product label (often about an hour before light rain exposure, up to 24 hours before painting) before considering the job done.
  11. On a double-hung or storm window, never caulk the bottom weep holes or drainage slots — sealing those traps water inside the frame.

Safety warnings

  • Use a stable, properly footed ladder for any window above ground level, and never lean or overreach — reposition the ladder instead.
  • If a window is on a second story or higher and you're not comfortable on a ladder at that height, this is a reasonable point to hire it out.
  • Wear gloves and eye protection when scraping old caulk overhead or at eye level, since brittle chips can flake off.
  • Work in a ventilated area — solvent-based caulks and cleaners give off fumes, and this is doubly true if you're working through an open window into an occupied room.
  • Check the weather forecast before caulking exterior trim; rain within the product's cure window can wash out an unset bead.
  • If old paint on the trim is flaking and the home was built before 1978, be aware it could contain lead paint — avoid aggressive sanding or scraping until you've assessed it.

When to call a pro

  • The wood frame or sill is soft, spongy, or crumbling when you press it, indicating rot that needs to be repaired before any caulk will help.
  • You find widespread water staining or damage on the interior wall below or beside the window, suggesting an active leak beyond a simple caulk gap.
  • The window or door frame itself is out of square, won't close properly, or has visibly shifted, which points to a structural or installation issue rather than a sealing one.
  • The job requires working from a ladder at a height or angle you're not confident with, especially on a steep roofline or second-story dormer window.
  • You suspect lead paint on pre-1978 exterior trim and the caulking job would require disturbing large amounts of that paint.

Cost estimate

$8-$15 per tube of exterior or interior caulk, roughly $10-$30 total for a typical few-window job with tools on hand

Sources