What do I need to know about choosing caulk?

Maybe you just moved into an older house, one that needs more than a few repairs. Probably many jobs involve cracks that need filling, and that means buying caulk and applying it in all the right places.

So you drive to the hardware store and they have enough caulk to fill all the cracks in the Grand Canyon after you reseal the windows of every house on your block.

That caulk aisle can be a trap, almost as confusing as the tape aisle.  So many brands and so many choices; actually, too many: sanded or unsanded; paintable or unpaintable; white, almond, black, bronze or clear; one year, five-year, 10-year or 30-year guarantees; 79 cents a tube or $8.99 a tube.

It’s my humble opinion that too many people count on caulk to do too much. Many base their use of caulk on the premise that if a little caulk does a little good, then a whole lot of caulk ….
Well, you know the rest of that story. And it’s not true! I never count on caulk to make my home improvement projects watertight or weatherproof. I want the mechanical attachments of dissimilar materials to be completely weather tight in their installation. Then a thin bead of caulk completes the aesthetic component.

The kind of caulk you choose depends on what you’re trying to do. Here are some common applications:

Window and door infiltration (in other words cracks) on your home’s exterior: We recommend polyurethane, sometimes referred to as butyl rubber. This type of caulking stays flexible and does not dry out or crack. It’s also very long-lasting.

But it’s a little harder to work with because it is so pliable – something like a stress ball that regains its original shape when poked. It also has very good adhesion (sticking) properties. But because it’s so sticky, you can’t drag your finger through it if it develops bumps and ripples and it can be tough to use a tool on polyurethane. So you want to be very careful applying this type of caulk. Practice, practice, practice, for example, before trying to caulk your front door jamb to the adjoining stucco.

This type of caulk can be painted over after curing for one week, but you cannot use it very easily on top of painted surfaces. It also comes in a variety of colors. You can also use this type of caulk to seal flashing and loose shingles. Use paint thinner or mineral spirits to clean up polyurethane. You’re likely to use this type of caulking frequently in our arid desert climate where cracking of wood, stucco and other substances is very common.

If you’re thinking of having your house painted soon, it might be easier to save this type of caulking for the painter to do.

Cracking on the interior of your home, especially around windows and doors:  Generally, you can use good quality latex caulk for this job as well as to seal baseboards, to handle minor cracks around tubs and showers, and to fill cracks or nail holes in dry wall. It can be used to fill around bathroom tile as well. It’s the easiest of caulks to use because it’s water-based. You can actually trim or smooth it with your finger. It can be cleaned up with water (not paint thinner), but it’s also water-resistant when dry. It can be sanded or painted.

Don’t use this type of caulk to fill cracks in tiles or to fill in where you may be missing grout between some tiles. This leads to a bigger problem you don’t want to deal with later.

Large cracks or joints around bathroom and kitchen fixtures: Use silicone for these jobs. Why not latex? Because the silicone will keep its seal when the joint or crack or gap stretches or compresses. Silicone is more durable and long-lasting and holds up well in temperature extremes. It is more difficult to apply than latex, but not as difficult as polyurethane. In cleaning up, you need paint thinner or mineral spirits. Pure silicone caulk will stick to painted surfaces but you can’t paint over it. However, they do make a paintable silicone caulk if you need it.

Generally, you need to buy a caulking gun and then a tube of caulk to put in the gun. Most caulks are fairly inexpensive – maybe $2 for a tube of latex, $5 to $6 for polyurethane, and $3   silicone. The problem is that once you open a tube, use it for some small job and then reseal it, the leftovers won’t last forever.

You can store a tube of caulk for a short while, but be sure to put a nail or piece of wire into the nozzle to keep it from plugging up with dried caulk. After inserting the nail, be sure to wrap the nozzle in several layers of masking tape.  In six months, though, the whole tube will be as hard as the granite on your countertops.So you’ve determined the right caulk for the job; you’ve purchased a good caulking gun.

You think you’re almost ready to go, but you’ve yet to answer the hardest question of all: Do I push or pull as I apply that bead of caulk?

###

This article originally published in the Arizona Republic on July 18th, 2015