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How to Seal or Caulk a Porch

Cody Sorensen

A porch has many, many joints that should be caulked to seal out moisture and bugs. The porch deck itself isn't caulked, but the face of the porch, the spindles, the ceiling and all trim work does need to be caulked. An acrylic siliconized caulk formulated for exterior applications is the one to use for this job, because its flexibility will allow it to expand and contract as the porch heats and cools with daily temperature variations. The secret to caulking a porch is cutting the tip of the caulk tube to the right hole size.

Caulking can extend the life of your porch.
  1. Use a wire brush to dislodge all loose or flaking paint. Dust every crack, joint, seam or gap that hasn't been sealed or caulked using a dust brush. Vacuum the dust out, if necessary.

  2. Load a tube of exterior acrylic siliconized caulk into a caulking gun and cut the tip of the gun at a 45-degree angle using a utility knife. Cut a little of the tip off at a time until you get the diameter hole size that you want. The best hole size for most sealing is between 1/16 to 1/8 of an inch.

  3. Get up on a ladder and caulk between the slats of the porch's ceiling. Caulk from side to side and smooth each bead of caulk with your finger. Wipe excess caulk off the slats and your finger with a damp painter's rag. Caulk the horizontal lines around porch's inner ceiling trim work. Move the ladder as many times as needed to accomplish the job. Apply a 2- to 3-foot bead at a time so that the caulk won't tack up before you can smooth it.

  4. Caulk the joints around the porch's columns, handrails, spindles and outer trim work. This task can take hours if the porch has particularly ornate woodwork. Caulk the trim work along the lower portion of the inner porch walls next to the house. Walk around to the front of the porch and caulk all trim work. If the handrails going up the steps are wood, caulk where the uprights connect to the rails.