How to Choose and Use Caulks & Sealants

Anyone who works on home remodeling projects will spend a lot of time with a caulk gun. Caulks are used to seal joints for a decorative finish, to seal joints to prevent water and air intrusion, or for both purposes. Whether you’re sealing joints in crown molding or weather-proofing window exteriors, choosing the right caulk/sealant product should be your first move.

Choices, Choices

Silicone sealants have long been the staple for exterior projects where a waterproof seal is necessary. This stuff is used around doors, windows, and any number of areas around the house to prevent air and water intrusion. Silicone-based sealants also work well for use in the kitchen and bath. These products can be purchased with antimicrobial additives to fight mold and mildew, and can be easily removed and replaced when the bead gets grimy.

However, standard silicone cannot be painted and is incredibly messy and sticky to use. Newer formulations of silicone-based sealants can be painted—but only if indicated on the packaging—so pay close attention when buying.

Acrylic caulk represents the other end of the spectrum. Unlike silicone, acrylic is only appropriate for interior projects and is not waterproof, nor is it very flexible and may crack over time. This is the stuff that has been used for years to fill gaps and cracks in molding and trim to give it a finished, cohesive appearance. Acrylic caulk is much easier to tool and clean up than silicone, and can easily be painted. Standard acrylic caulk is a strictly cosmetic product, however, and not intended to serve as a sealant (but acrylic is also the least expensive option).

These days, many hybrid caulk/sealants stock the shelves of the hardware store. These products come in formulations containing some of the attributes of both silicone and acrylic, meaning they can be cleaned or tooled more easily than standard silicone, remain more flexible than acrylic, can be painted after application, and still retain a waterproof seal.

Pro-grade polyurethane-based sealants present another option for exterior siding, windows and doors, because they stay flexible and don’t shrink, have better adhesion than silicone—plus, they’re paintable.

Water-based and solvent-based caulk/sealants further complicate the wide selection, offering similar hybrid properties, and many serve double-duty as adhesives.

With such a multitude of formulations, product selection can be confusing.

The easiest way to make sense of all the options is to pay close attention to the indications on the packaging. Make sure the caulk/sealant tube is clearly marked for the task at hand and intended for interior or exterior application. Whether the product is elastomeric, flexible, waterproof, paintable, cleans up with water, or contains a mildewcide additive, all features should be listed prominently on the label.

Application

Cut the tip of a caulk tube at a straight 90-degree angle and keep the hole small. You can always re-cut to make the hole bigger, but you don’t want to sacrifice control of the bead. Many caulks/sealants also have an interior seal inside the nozzle that should be punctured several times with a stiff wire or thin rod.

Before applying any caulk or sealant, clean the surface of the work area thoroughly to prevent dirt and debris from disrupting application of the bead. A dirty surface will also prevent adhesion of the caulk. When laying the bead, keep the gun positioned at a 90-degree angle to the wall to strike a balance between pushing and pulling for consistent application. This position also provides easy visibility on both sides of the nozzle.

Rest the nozzle tip evenly on both sides of the joint. Move the caulk gun at a steady rate. Keep the bead width as steady as possible and leave no gaps. If you cross any vertical joints, take the time to caulk a few inches up or down the joints, which will make it easier to connect the caulk beads later.

Complete the task by tooling the bead. Hardware stores sell caulking tools of various profiles and sizes to strike off excess caulk and give shape to the bead. You can also make your own tools to shape concave beads by using wood dowels of various sizes, or simply slap on a rubber glove and use your finger. Plastic grocery bags make fine receptacles for the excess caulk.

How to Seal Big Joints

To seal a joint larger than 1/4-in. wide, use a foam backer rod as a filler before applying the caulk. Simply press the flexible backer rod (a.k.a. filler rope) firmly into the joint or crack and apply caulk on top of it. The inexpensive backer rod provides a cheaper way to fill the empty space than using caulk alone. Plus, when caulk is tooled over a backer rod, it forms an “hourglass” shape with large surface areas of adhesion at the sides of the joint. The hourglass shape of the caulk bead withstands joint movement better than any other configuration.

DuraMaster Elastomeric Caulk/Sealant

The new DuraMaster formula from Titebond offers 100-percent joint-movement capability, so it will flex and stretch and won’t crack or detach from the surrounding building materials.

Movement occurs with expansion and contraction of building materials due to temperature changes, settling, wind and seismic events, and this movement is why brittle caulks can crack or fail over time. Typical elastomeric sealants can handle movement of 25 percent of the original joint size and are rated Class 25 (the minimum rating for handling a moderate amount of movement). DuraMaster, however, has earned the highest ASTM C-920 rating for sealant performance, Class 100/50, which means it can handle movement of 100 percent expansion and 50 percent contraction. The Class 100 rating is a testament to the sealant’s durability, because according to Titebond, the new formula tested four times more durable than other water-based sealants. Plus, it will span even large gaps, up to two inches wide.

The DuraMaster sealant can be used for interiors or exteriors. Its water-based formulation is good news for anyone who can’t stand dealing with the sticky, goopy, difficult-to-tool, and nearly impossible-to-clean mess of silicone-based products. The new formula is simple to tool and cleans up easily with water (until the sealant dries). And unlike standard silicone, DuraMaster is a paintable caulk and is sold in 13 colors. As far as sealants go, our staff gives DuraMaster a big thumbs up, and now that it’s widely available, you can try it yourself. Learn more at www.titebond.com.