Sealing Joints

Adequately seal joints to keep moisture from infiltrating where it can damage sheathing and the back of siding.


Keeping moisture from infiltrating where it can damage sheathing and the back of siding is relatively simple. The usual problems are inadequate or poorly installed caulking around windows, doors, gable trims, and other joints. Take the time to inspect all the places where water could get in and apply high-quality caulk where needed. The exception is vinyl siding, which should be caulked only in those places where vinyl pieces abut wood or metal surfaces.

Also check your home's flashings. Check whether you have flashings where they are needed--above doors and windows, at vertical joints of panel or board-and-batten siding, and at the top of a water table. If you are missing some flashings, consult with a professional to see if you should remove siding pieces to install flashing or if you should simply caulk the joint well.

Prestart Checklist

An hour or two to replace damaged flashing or apply caulk around several windows or doors

Caulking gun, tin snips, lineman's pliers, flat pry bar, hammer

Caulking, a skill that you can learn with 15 minutes or so of practice

Inspect around windows, doors, and trim boards to see if you need to replace flashings or apply caulk.

High-quality exterior caulk, flashings as needed, nails

Repairing Flashing: Step 1

If old galvanized flashing above a window or door is rusting or if flashing is damaged or the wrong type, pry away the top molding. Use scraps of wood to protect the window and siding as you pry.

Repairing Flashing: Step 2

Carefully pry out the siding as needed to get at the flashing underneath. Use pliers to pull out nails and the flashing.

Repairing Flashing: Step 3

Use tin snips to cut new aluminum or vinyl drip-cap flashing to fit.

Repairing Flashing: Step 4

Prying away the siding as needed, slip the new flashing in place. There is no need to nail it. Replace the trim and nail the siding back down.

Applying Caulk: Step 1

Use a utility knife to cut the tip off the caulk tube. The farther from the tip you cut, the thicker the bead of caulk. Some people prefer a strongly angled cut, and others prefer one nearly perpendicular. Place the caulk tube in the gun.

Applying Caulk: Step 2

Practice on scrap pieces if you are unsure of your skills. Hold the tube's tip against the joint, squeeze the gun's trigger, and start moving downward once caulk starts to come out. Aim for smooth motions, continually squeezing the trigger to produce smooth lines. When you get to the end, unhook the lever to stop the flow.

Applying Caulk: Step 3

If the caulk is well adhered on both sides of the joint and the line is to your liking, you can leave it. If you want a smoother or wider line, smooth with your finger or follow the tips offered in the next slide.

Smoothing Caulk Lines

Some people prefer to smooth caulk lines using a tool made for the purpose. Several tools are available. A tightly wadded rag (above) dampened with water (for latex or acrylic caulk) or mineral spirits (for oil-base caulk) is one option. You'l need to periodically rewad and clean the rag.

Comments (1)
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