Caulks and Sealants: Choosing the Right Type

A smooth rod caulk gun, loaded with a cylinder and ready to use.

Knowing is half the battle when choosing the ideal materials to work with, and using the right material is crucial to making caulking easy. Caulks and sealants come in many different types, and they are ideal for a wide variety of projects. Learn more about these types so that you can choose the right caulk or sealant for your next project.

Water-based Caulk

Generally referred to as latex caulks and sealants, water-based caulks are the easiest to work with because they apply easily, are paintable, have little odor, and clean up with water. They're effective for filling gaps in baseboard and trim, as well as for caulking around interior window and door frames. Most often they come in cartridges ranging from 10 to 12 ounces as well as convenient squeeze tubes ranging from four to six ounces. For latex caulks, your ideal curing conditions are warm (above 40 degrees), dry weather.

Within this category, there are several more specific caulking types with specialized characteristics. Vinyl latex caulk is usually effective for five years and is most effective on small cracks in baseboards and little gaps around windows. Vinyl latex is non-flammable and paintable but not very flexible, and it hardens over time.

Acrylic latex caulk is a general-purpose caulk—more flexible than vinyl latex caulks. It is easy to apply, non-flammable, and cleans with water. It adheres to most surfaces—best on wood and masonry—and it can be painted shortly after application. It is available in pigments as well that allow it to match many surfaces. It remains effective for 10 to 15 years, however, it is not recommended for an area that is subject to excessive water collection like tubs or sinks. It is flexible and maintains that flexibility over time. It should not be applied in temperatures of less than 40° F.

Tub and tile caulk is a specialty performance caulk with added mildewcide to protect against mildew growth in areas prone to moisture (kitchens, bathrooms). Some tub and tile caulks are more flexible and crack-resistant, too. Many formulations include adhesives that combine a sealant and adhesive in one. Like other latex caulks, they apply easily, are non-flammable, clean up with water, and are paintable. They are also available in a variety of colors.

Siliconized Acrylic Caulk

This type of sealant combines silicone with acrylic latex formulas for improved water resistance. This medium-performance, water-based caulk can withstand greater movement than acrylic latex, and it can be used for interior or exterior with good adhesion, even to glass and ceramic tile. This caulk also comes in a variety of colors as well as clear formulas.

Like the former water-based sealants, it applies easily (though best applied in temperatures above 40° F), is non-flammable, paintable, mildew-resistant, and cleans with water. It can endure moderate temperature changes and has a total life expectancy of about 25-35 years.

Silicone Caulk

Silicone caulk is another alternative to using tub and tile latex caulk. It is good for use around bathtubs and sinks because it resists mold and mildew, and it is water resistant with excellent adhesion to smooth surfaces such as metal, glass, and tile. It should be noted, however, that it does not adhere to masonry. Silicone caulk remains flexible after curing and is not affected by UV radiation. Unlike water-based sealants, though, paint will not stick to most silicones and this caulk is more difficult to apply.

Silicone does not adhere well to wood, and must be cleaned up with solvents rather than water. It is non-toxic, though, and can be applied at nearly any temperature.

Polyurethane Foam

This sealant is used for a variety of jobs, most often around electrical outputs, pipe penetrations, and in large voids or openings where the elements can infiltrate a structure. It expands to fill gaps, holes, and voids and is good for insulation purposes. Polyurethane foam also comes in different expansion rate formulas, and it is easy to apply, cures quickly, is paintable, and offers good adhesion.

Butyl Rubber Sealants

Butyl rubber sealants are solvent-based with a life expectancy of only two to 10 years. However, be that as it may, this choice is a good one for sealing out water in lap joints, such as gutters, and for metals and masonry as well as outside for chimneys. It's probably the best waterproofing sealant for below-grade applications, such as foundations.

That said, these sealants are also stringy, difficult to apply, and slow curing. They are most efficient when applied to openings between similar surfaces, but are not recommended for openings wider or deeper than 1/4" or in 90° corners. Butyl rubber sealants also offer low to moderate movement capabilities.

Synthetic Rubber Caulk

A relative newcomer to the caulk category, synthetic rubber caulk is perhaps the most flexible product on the market. It cures clear and is ideal for exterior joints that typically expand and contract since it can be applied in adverse weather conditions (wet and cold) and stretches and recovers easily without breaking. It is also great for use on roofs, wood siding, and joints that frequently show movement.

Synthetic rubber caulk can be painted with latex paint. Due to higher VOC content, it can’t be used indoors in some parts of the country, although manufacturers have introduced low VOC formulations to the marketplace.

Modified Silicone Polymers

This type of sealant delivers excellent performance on vinyl, fiber cement, aluminum, and wood siding. It combines the best characteristics of polyurethane, silicone, and water-based products, offering permanent flexibility. It's also great for applying in wet weather, low temperature applications, and for caulking around exterior windows, doors, and vents. Modified silicone can be painted with latex paint.

Caulk Gun

Now you know all about the wide variety of caulk types, but a caulk gun is similarly important when considering a DIY project, as it is the best, easiest tool for sealant application. Caulk guns come in different kinds as well, but unlike the sealant itself, there are only three.

Ratchet guns are less expensive, but are more difficult to use. These stop caulk flow by requiring that the user turn the piston so the ratchet disengages.

Smooth rod guns are more expensive, but easier to use. With a smooth rod gun, the user simply disengages a quick-release thumb plate to stop the flow of caulk. Drip-free smooth rod caulking guns allow the piston to back up slightly after each squeeze so the user does not have to turn the piston or depress a lever to stop the flow of caulk. Some models use an automatic vacuum action to draw any unused caulk back into the nose of the tube.

Power guns that operate with a rechargeable battery pack are obviously the most expensive variety, but they are becoming popular with pros and serious DIY enthusiasts for their ease of use.

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