A gap between a baseboard and a wall can be especially bothersome and very noticeable, particularly if it is found in a well-traveled area of the home. Not only is it unattractive, but it creates a space into which things can fall inadvertently. More than likely it was caused by an uneven space along the wall or a slightly warped baseboard. It usually does not mean that the baseboard is pulling away from the wall, so a simple fix is what is required. Unfortunately, you cannot paint over it. That wouldn’t solve the problem anyway. The best thing to do is fill the gap with paintable caulk. It is an inexpensive fix that can be done in practically no time.
Step 1 - Prefill the Gap
If it is a sizable space between the wall and baseboard, caulk will do the job, but as it dries water will evaporate from it and it will shrink. This will leave you with another gap, albeit a shallower one. So if the space is large, you'll want to start by stuffing a thin strip of foam into it. Make sure the foam does not protrude from between the wall and baseboard. It should be situated about 1/8 of an inch below the surface.
Step 2 - Load the Caulking Gun
Load the new tube of paintable caulk into the caulking gun. It is particularly important that you make sure the substance you're using says "paintable"—otherwise, you won't be able to blend it with the color of your walls. Paint will not stick to silicone caulk and other non-paintable types very well. You'll end up with a sloppy look before long.
Pull the ramrod on the gun all the way back and slide the tube’s nozzle through the hole in the front. Then, slide the ramrod’s disc into the back of the tube. Don’t apply too much pressure yet.
Step 3 - Cut the Tip Off of the Tube
At an angle, cut the tip off the tube of the caulk with the utility knife. The opening cannot be too big or else the bead of caulk will be overwhelming, so make it about 1/8-inch wide. Now bring the ramrod up to the back of the tube and squeeze the trigger a few times until the pressure forces some caulk out.
Step 4 - Lay the Bead of Caulk
Hold the gun at about a 30-degree angle with the open tip right on top of the gap where you will start, and make sure when you pull the trigger that a constant flow of caulk will come out. However big the gap is, plan on squeezing out a bead of caulk no longer than two feet. Apply the caulk evenly for this length, sliding the tip of the tube over the gap before you let up on the trigger. Some caulking guns will force the tubes to run, wasting material. If this is the case, set the gun upright to minimize the loss.
Step 5 - Smooth Out the Bead
Run your bare finger over the bead to smooth it out and blend it between the baseboard and the wall. Follow this with a moistened sponge that has been squeezed out for a better blend.
Step 6 - Remove Excess Caulk
If any excess caulk drips or runs along the wood or the wall, immediately use the putty knife to carefully scrape it away.
Repeat these steps over the entire gap. It is important that the bead of caulk, when applied, extend slightly above the gap so it can be smoothed into it. Again, if the gap is especially big, stuffing a piece of foam inside it before the caulk can help with the shrinking effect after it has dried. Don’t attempt to paint over the caulk until after it has fully cured.