Types of caulks and how to use them
Many types of caulks and sealants are designed for specific jobs. Choose the wrong one for a job and you’ll end up with sloppy results and premature failure of the bond. With the right product applied correctly, you’ll get a professional result that will last as long as it should or longer. Here are some of the most popular types of caulks:
Acrylic latex caulk
Probably the most used product, acrylic latex caulk is intended for interior projects, including filling small cracks and gaps in trim before painting, sealing the gaps between wood molding and drywall, and filling small countersunk nail holes before painting. Acrylic latex caulk tools easily with a wet finger, scraper blade or any type of caulking tool, and cleanup is simple with just a little water or a damp rag.
Silicone latex caulk
Intended for exterior applications such as sealing the gap where siding meets windows, Silicone latex caulk has a silicone additive that helps it perform well in areas exposed to water. Even with the silicone additive, these caulks can typically be painted over.
Many silicone latex caulk can be easily cleaned with water and soap, but some may require mineral spirits or a similar product to clean tools and hands. Silicone latex caulk is not recommended for use on surfaces that are exposed to large amounts of water, such as shower joints.
Pure silicone caulk
Designed to perform under heavy water exposure inside or outside a building, pure silicone caulking is often used to seal kitchen sinks, toilet bases or tile joints near bathtubs. Silicone caulk can also be used to seal around venting or plumbing penetrations on exterior walls or roofs.
Pure silicone caulk products usually have good adhesive properties and can be used to adhere granite countertops to sub-bases. It cannot be painted, but comes in clear or different colors to match or complement interior or exterior finishes. Tooling silicone caulking can be tricky because of the stickiness, and cleanup requires mineral spirits or a similar product.
Concrete crack filler is usually a type of silicone latex caulk formulated to look like cement when it’s dry. Although it’s ideal for fixing cosmetic cracks, it is not designed for structural repairs or to prevent water intrusion through foundation cracks.
Construction adhesives are specialty caulking products designed for specific purposes. Subfloor adhesive, drywall adhesive or wood trim adhesive are good examples. Some construction adhesives are suitable for exterior applications and have waterproofing qualities; others are not. Tooling is usually not an issue as they are usually applied between two mating surfaces. Cleanup varies from simple water to mineral spirits or acetone.
Roofing cement or flashing caulks are designed to handle simple roofing repairs and seal around flashing elements on roofs. These are especially durable and formulated to last under years of sun and rain exposure. Tooling and cleanup can be difficult as roofing cements or flashing caulks are extremely sticky. These products typically cannot be painted.
Rope caulk is not actually a caulk, but rather it’s a glazing material that is similar to soft clay. It can be shaped and molded to fit into the area and is typically used around windows.
Application tips and tricks
Always read the product label to make sure the material you want to use is suitable for the application. Avoid trying to fill cracks that are larger than ¼-inch, as that typically leads to cracking as a result of shrinkage and expansion. Some caulks are suitable for filling large cracks and voids, but require a foam backer rod to save on caulking material and provide a flexible backfill material to completely fill the crack.
Always caulk on a clean, dry surface, unless the product specifically says it can be applied under wet conditions. To create straight, sharp lines, mask off the surfaces on either side of the joint to be caulked with blue painter’s tape, tool the caulk smooth and then remove the tape before the caulk dries.
Be careful to only cut the tip of the caulk tube to the smallest opening possible for the job, and maintain smooth constant pressure on the caulk gun trigger to release a steady bead. Work at a slow and consistent speed to lay a smooth bead.
Only apply as much caulk as you need to fill the joint. Avoid overfilling or squeezing out too much caulk, as that leads to more cleanup and a messy job.
To smooth caulk joints, wet your finger with water (for latex caulk) or mineral spirits (for silicone and silicone caulk) and work from one end of the joint to the other with firm, steady pressure to work the caulk into the joint. When you begin to build up an amount of caulk on your finger, clean it with a rag dampened in water or mineral spirits, then re-wet your finger and continue.
—By Rob Fanjoy