Caulking Techniques for Do-it-Yourselfers

Before painting a room it's a good idea to caulk between trim molding and walls first. This will greatly improve the quality of the finished paint job. Take care when choosing caulk for wood trim and other painted surfaces. Use a paint-able latex or silicone enhanced caulk, not pure silicone, for painting projects. Pure silicone caulk will repel paint and should only be used for caulking bathroom tubs and tile and similar non-painted surfaces. Both types of caulk will set (become firm) in about an hour and cure (become hard) in about 24 hours. You can paint latex caulk after it has set but be careful not to dig into the bead with the brush bristles.

The first step to caulking is to remove any loose material from the gap between the two surfaces. Wedge a putty knife or similar tool between the wall and trim and drag it down the length of the crack to remove loose plaster and paint. Sometimes a putty knife can be slipped under the old caulk and the whole bead can be removed at once. If the old caulk is cracked but not coming off, trim the crack out with a sharp drywall knife. Cut cleanly thru the caulk but avoid cutting into wood trim or the wall surface. Pull the loose caulk free.

The gap to be filled with caulk should be no wider than about 3|8in. If you have spaces wider than this, insert a strip of wood with a little caulk applied into the gap to fill the extra space.

Cut the applicator tip of a caulk tube at an angle far enough down to make about a ¼in. opening. There is a foil seal where the applicator tip meets the tube, pierce this with a long nail or the peircing rod included on some caulk guns. Insert the tube into a caulk gun and push the plunger down so it makes contact with the push plate inside the tube. Squeeze the trigger to start the flow of caulk from the tip and then insert the tip into the crack, starting at one end. Squeeze the trigger and wait for the caulk to flow before drawing the gun slowly along to fill the crack. In some situations it may be easier to push the caulk gun along the crack rather than pulling it as illustrated here. We don't recommend the pushing method because it can be difficult to monitor the caulk flow causing gaps in the bead. Recaulking to fill the missed spots can cause problems with excess caulk.

Pull the gun along the crack so that a bead of caulk just fills the space between the two surfaces. Watch for excess caulk that may run quickly from the tube. If this happens, pull the caulk gun faster to spread the excess caulk.

Caulk a couple of feet and release the pressure on the caulk gun to stop excess caulk from oozing out. Turn the shaft and pull back to disengage the plunger.

Wet an old cotton t–shirt or similar cloth and squeeze out the excess water. With your index finger inside the cloth, run over the caulk to smooth it out while pushing it deeper into the crack. Turn the cloth to a clean spot frequently to avoid a buildup of excess caulk. Wipe any caulk from the wall and trim surfaces with a clean spot on the cloth as you go. After the caulk has been smoothed out, be careful not to disturb it until it has had time to set and cure.

Continue caulking a few feet at a time. Use the cloth to smooth each new run of caulk into the last. Rinse the cloth frequently to remove collected caulk and avoid spreading it to unwanted areas.

Let the caulk set for about an hour before painting. The bead will not be hard for about 24 hours so be careful not to disturb it with the brush bristles or the roller.