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How to Caulk

by: Paul Kando

The average Maine house leaks � warm air out, cold air in. We audited homes that had leaks equivalent to a door being left open 24/7 and even the average of the first 100 houses audited has an equivalent leakage area of 2� to 3 square feet. That�s a large hole and if it were a door or a window, we would have surely closed and sealed it long ago. Instead, the hole is made up of many small leaks, most of them easy to fix, but often hard to notice individually. An energy audit will mark these leaks for you, so you can fix them. They come in many shapes and sizes. Large leaks, around pipes coming up through the floor, for example, can be sealed with expanding foam. Today, however, we are concerned about the many small cracks and leaks around the house that you can fix yourself by caulking.

Caulking cracks is not hard to do. Still, if not done properly, the caulk may not hold up or the finished job may look sloppy. Here is one way to caulk properly, beginning with the right tools: caulking gun, putty knife, razor knife, cotton rags (old T-shirts are a good source), bucket. For best results, chose a good quality caulking gun, the difference in price will be worth it. The cheap ones have notches in the plunger rod. The better ones have smooth rods. A smooth-rodded gun will provide you with much better control by metering out less caulk with each squeeze of the gun.

Painted surfaces are easier to clean after caulking, so, with new woodwork it is best to caulk after the wood have been primed. When caulking old work, it is important to remove any old, cracked caulk first. And the gap to be caulked and the adjacent surfaces must be free of dust and loose particles or the caulk will not adhere. Select the right caulk for the job. In dry areas acrylic latex caulk is fine and it cleans up with water. In wet areas use silicone, which will clean up with alcohol.

In applying caulk, it is important to remember that the idea is to force the caulk into the crack to be filled � it is not enough to have it adhere to the surfaces on either side. Therefore, a good caulking job begins with cutting the right sized opening in the tip of the caulk-tube. Most do-it- yourselfers cut this hole too big, resulting in a messy job and a lot of caulk wasted. It is also harder to force the caulk into the crack when the hole is too large, as the pressure is reduced. A good sized opening, cut at a 30-45 degree angle (usually indicated by lines on the caulk tube), will have a diameter of 1/16" to 1/8". If the opening is too small, the caulk will not fill the crack properly. If it is too large, the job will be more difficult to keep neat and caulk will be wasted. Snip off the tip of the tube at the right marking and don�t forget to punch through the inner lining, using the piercing needle attached to most caulking guns.

The job begins with partially filling the bucket with some warm water (denatured alcohol if you have to use silicone). Hold the caulking gun at a 45� angle relative to the crack you are caulking. Squeeze the handle so an even amount of caulk flows from the tube. You want the bead of caulk to be slightly higher than the top of the gap or crack. Applying some pressure, slide the gun along the top of the crack at a slow, even speed as the caulk exits the tube. If you move too quickly, the caulk will not fill the crack, if you move too slowly, a lot of caulk will build up atop the crack which will have to be cleaned away.

caulking with spoon
Smoothing Caulk with spoon
photo credit: woodzone.com

Caulk no more than 2-3 feet of crack at a time. Then set the caulk gun down, making sure that the tension is released and the caulk stops flowing. Wet your finger in the bucket and, applying some pressure, smooth the bead of caulk. If you chose the right sized hole and caulked at the right speed, there will be very little caulk left on your fingertip when you are done. Wipe your finger clean with the wet rag. (If you�d rather not use your finger for this task, try using he back of a wet teaspoon, as shown below.) Rinse out the rag, squeeze out all the water and immediately wipe it across the caulk joint to feather the edges and remove any excess left behind. Rinse the rag and repeat if necessary. Glide the rag softly across the caulk so as not to remove any caulk from the gap. Remember: the rag must be moist, not dripping wet, else it will remove the caulk you have just applied.

An alternative technique is to mask both sides of the crack with blue painter�s tape before applying the caulk, using long strips, evenly aligned, parallel to the crack. Remove the tape immediately after smoothing the bead of caulk with your wet finger. This will result in a very neat job, with little cleanup to be done. But, of course, it will take longer also. For this reason, I use tape only in critical areas, where I do not want the caulk to get on an adjacent surface at all.

If you want to paint after caulking, wait until the caulk has set, otherwise you paint brush will remove the still soft caulk. To see how long to wait, read the instructions printed on the tube of caulk.

Practice makes perfect. Start caulking somewhere � laundry room, inside closets � where the neatness of the result is not as critical. Get the hang of the proper speed, the right sized opening in the tube-tip, the best angle to hold the gun, etc. Then graduate to doing the more visible jobs.