Caulk is used to create a waterproof or insulating seal between building materials. Examples where caulk is used to fill a gap include: between a tub and tile, countertop and backsplash, or window and frame. Although applications may seem similar, the key to a successful seal is to make sure you use the correct caulk for the job.A bead of caulk should be thin and consistent. The best caulking jobs are the ones you don’t notice, so apply the caulk sparingly and clean up any residue quickly before it dries. [Check out our advice on how to remove old caulk and the right way to caulk a tub.]Kitchen and Bath CaulkThis caulk needs to be water resistant to prevent mold and mildew buildup. Look for a siliconized acrylic or polymer caulk. They are often called kitchen and bath or tub and tile caulk. Siding, Windows, and Door CaulkThere are a variety of caulk compounds that will create air and watertight seals around windows and doors. These include polymer, silicone polymer, paintable silicone, and butyl rubber caulks.Concrete CaulkThis type of caulk should be used where concrete slabs meet or where they meet with a building. A polyurethane caulk works best here, but silicone will also do.Glass CaulkSilicone and siliconized acrylic work best for glass. But read the label to make certain it adheres to glass surfaces.Gutter CaulkGutter sealant or caulk will be called butyl rubber. This caulk is ideal for below grade applications and outdoor waterproof needs.Roofing CaulkRoofing caulk is available in gun grade or brush grade, based on how it will be applied. This polymer caulk must adhere to metal, masonry, or asphalt roofing materials.Timothy DahlDIY EditorTimothy is a lifelong DIY enthusiast who is fixated on smart home tech, beautiful tools, and wrenching on his FJ62 Land Cruiser. He’s the DIY editor at Popular Mechanics and also the founder of the home improvement site, Charles & Hudson, the Webby-nominated family site, Built by Kids, and Tool Crave. When not working, you’ll find him on his board or bike enjoying the LA weather with his family and friends. Follow him on Instagram and Twitter.
