If your project calls for caulk, you can probably picture yourself at the home store facing a towering wall of caulk tubes that all look alike. We've all been there. The good news is that there's a right caulk for the job; you only have to know what to look for and read past some misleading labels to find what you need.
Caulk vs. Sealant
Before going a step further, you might have heard caulk called a sealant and vice versa. Technically, the two serve the same purpose—sealing a space, making it airtight or waterproof. But there is a significant difference between them; sealants are used on objects that shift or move, like windows, for example. A sealant is used when you need more elasticity so it can shift with the moving object it's sealing. Meanwhile, caulk is best suited for filling the space where the shower tiles meet the top of the bathtub—both surfaces are stationary. Also, caulk's significant benefit over sealant is that acrylic latex can be painted on, while sealant can't.
Types of Caulk
Caulk comes in many options: different colors, fast-drying, and sanded vs. unsanded. Sanded, grainy-textured caulk works best sealing wet spaces and large gaps of 1/8-inch or more. Unsanded has a smooth texture and appearance, working best on kitchen countertops and backsplashes.
Caulks are water-based, like acrylic or latex, or solvent-based, like polyurethane, silicone, or butyl rubber. Solvent-based caulks require mineral spirits or other strong solvents to remove them, while acrylic and latex products do not. Also, you can get caulks that are a hybrid like silicone and polyurethane combined.
Here's an overview of some of the main types of caulk and their different uses.
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Acrylic Latex Caulk
Acrylic latex caulk is the general-purpose workhorse. It's inexpensive and fast-drying and is useful for many different applications. Most importantly, it can be painted and is sometimes termed "painter's caulk."
Use this caulk for filling small gaps and blemishes in wood trim and for sealing joints between wood parts that you will paint. While the label may claim it's suitable for wet areas, it's best to stick to dry areas or on parts that may see moisture (like exterior trim and siding) but will be protected by a complete coating of paint.
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Latex or Acrylic Caulk With Silicone
Latex or acrylic caulk with silicone added offers somewhat more moisture resistance than standard latex caulk. Thanks to the silicone, it's also a bit more flexible and durable. You can use this in the same places as standard latex caulk and for exposed (unpainted) applications that need only moderate waterproofing.
While this caulk is commonly called "tub and tile" caulk, it's not as good as pure silicone for tile and bathroom fixtures.
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Pure Silicone Caulk
Pure, or 100 percent, silicone is the premium caulk for jobs exposed to water. Silicone caulk is expensive but worth the cost due to its flexibility and long life. Most formulas are mildew-resistant and have inhibitors to slow discoloration (but all caulk gets ugly over time). The only big downside is that it's not paintable. But that shouldn't be a problem for its typical applications. If a silicone caulk says you can paint it, it's probably not pure silicone.
Use pure silicone for sealing around plumbing fixtures, such as sinks, toilets, and faucets, and for any caulk joints on the tile in wet areas. It's also a general-purpose sealant and waterproofer for holes in exterior walls, sealing around pipe and wiring penetrations, and filling gaps between exposed materials of almost any type. Finally, pure silicone is a pretty strong adhesive and can be used as glue for under-mounted sinks or fixtures attached to stone and other hard-to-glue materials.
Silicone will work on roofs and windows or doors, but it's not the best option for those applications. Instead, use a high-quality roofing sealant for roof work, and use a high-quality window and door sealant (not latex caulk) for installing and sealing windows and doors. (It lasts as long as silicone and is paintable.)
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Butyl Rubber Caulk
This sticky, messy caulk is primarily for outdoor use. It's an excellent sealant for metal and masonry and for joints that might move due to expansion and contraction. A good example is gutters. It also fills larger joints nicely when used with a caulking rod or backer rod. Many formulas are paintable.Continue to 5 of 6 below.
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Also called fireplace caulk, refractory caulk is a high-temperature sealant suitable for filling small cracks in brick, concrete, and other masonry materials, specifically in masonry fireplaces and chimneys. Use this only for minor repairs, such as filling tiny gaps between bricks in a firebox. It's not suitable as a masonry replacement or for significant repairs.
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Masonry Repair Caulk
This flexible caulk is primarily used for sealing cracks and expansion joints in driveways and other outdoor concrete surfaces. It's also suitable for filling and repairing cracks in masonry-stucco walls. Today, many formulas are made with polyurethane (or different urethane blends), and some contain sand to provide a masonry-like texture.
Is silicone or acrylic caulk better?
The answer depends on what you're using it for. Silicone is your go-to whenever you're sealing something water-related—bathrooms, kitchen fixtures, bathtubs, even fish tanks. Acrylic is a good general-purpose sealing substance, perfect for tiny gaps between baseboards and chair rails. When still wet, you can wipe away acrylic caulk with some water. However, it dries faster and gets harder than silicone, and you can paint over it.
How do I know what kind of caulk to use?
Many manufacturers make different product lines specifically for certain tasks. Read the label to figure out what its manufacturer suggests it's best for. Rule of thumb: Consider where you will use the caulk. Products with silicone work best in water-prone areas. Latex acrylic is suitable indoors for use with wood on drywall. Butyl rubber works well outside, standing up to the elements, and is often used for handling roofing and gutters.
What caulk is good to use for the house exterior?
Several types of caulks are used for sealing home exteriors like siding, gutters, roofing, and masonry. Silicone caulk or a silicone-latex hybrid is excellent for exterior windows, doors, trim, and siding. Butyl rubber is best for outdoor use such as around gutters. It's gooey and hard to apply, but it stands up to abuse from the pounding sun and icy or snow-filled days. Masonry repair caulk is primarily a urethane-based blend that fills cracks in masonry nicely.