Choosing the right caulk for your job can be difficult. With latex, silicone, polyurethane, butyl, and hybrid varieties out there, how do you know you’re pulling the right tube off the shelf? Asking yourself a few questions about the project will help direct your choice to a caulk that will greatly improve the project’s look and functionality.
Before we start with a few questions, remember that caulks serve a specific purpose. Caulk is intended to seal joints and small passages in a home, keeping out water, air, noise, and insects. Caulk can also improve the appearance of unfinished joints and exposed cracks. Caulk should never be used in the following ways: as a filler to patch holes, in large installations, as replacement for grout, or as an adhesive.
Consider these things before your caulking project begins:
Question 1: How long does the project need to last?
This may seem like an odd question at first, but let’s realize that a prop for a week-long theater production doesn’t require the same longevity as caulking windows of a home.
Question 2: What materials are you sealing together?
If you’re sealing wood-to-wood, that’s a different situation than metal-to-glass. Choosing a caulk with the right capabilities is critical to the long-term success of your project. Nearly every tube of caulk on the market will give instructions on how the surfaces must be clean, dry, and free of debris. This is for a good reason: caulk failure can often be traced back to a surface that didn’t allow the caulk to adhere correctly. Never apply new product over old caulk. Whether you use a brush, scraper, or razor blade, remove any old caulk before applying new caulk. Then, clean the surface and wipe with a clean cloth. Assuming your caulk requires a dry surface, make sure the area in question is free of soap, grease, dust, and other contaminants that could keep the new caulk from adhering properly.
Question 3: How big are your gaps?
When applying caulk, it’s important to remember that it was designed for small gaps. Ideally, your caulk will span a gap that is about half as deep as it is wide. Use a backer rod for large gaps, which is made of foam and comes in different thicknesses. If you’re using backer rod, choose the closed-cell foam which won’t soak up water like its open-cell cousin. Next, carefully insert the backer rod into the gap by hand or with the help of a blunt instrument—you don’t want to pierce the backer rod foam and create an unintended pathway for water.
Basic Guidelines for Common Types of Caulk
Now that you’ve reviewed the specifics of your project, here are basic guidelines for some of the most common types of caulk. The terms “latex” and “acrylic” are virtually synonymous; you’ll see many manufacturers call their product “acrylic-latex.” Don’t be discouraged from buying it if the caulk meets your project’s needs. Consider outside temperature as well as the temperature of the caulk itself. If a tube sits in your vehicle during freezing temperatures, that’s likely a problem.
Silicone
Silicones are long lasting, durable, flexible, and allow a large degree of joint movement. While silicones are available in clear and a few different colors, most silicone caulks are not paintable. Silicones do offer a waterproof seal that is also very resistant to mold and mildew, making them a common choice for bathrooms and kitchens. Silicones adhere to many surfaces, so check the label to make sure it’s compatible with your substrates. Silicones can be hard to clean up if it gets onto tools, hands, or unintended surfaces.
Use silicone caulk for: Outdoors, bathrooms, kitchens
Adheres to:
- Glass
- Ceramic
- Fiberglass
- Porcelain
- Non-oily woods
- Canvas
- Most metals
- Most plastics and rubbers
- Painted surfaces
Polyurethane
Polyurethanes bond well to most surfaces, and offer very good flexibility. They come in a variety of colors and are paintable, though there is not a clear polyurethane caulk available. Polyurethanes can also be difficult to clean up, but adhere to a wide variety of substrates.
Use polyurethane caulk for: Joints subject to abrasion
Adheres to:
- Wood
- Concrete
- Metal
- Vinyl
- Aluminum
- Stucco
- Asphalt
- Fiberglass
- Masonry
- Brick
- Stone
- Plastic
Acrylic Latex
Sometimes called “painter’s caulk,” an acrylic latex caulk can be a great choice for an interior application. They are easy to use with a caulk gun, easy to work with, clean up quickly, and are paintable once cured.
Use acrylic latex caulk for: Patching interior cracks, joints, and small holes; sealing interior window and door frames
Adheres to:
- Wood
- Brick
- Drywall
- Metal
- Painted surfaces
- Most common building materials
Latex with silicone
As the name suggests, these caulks are much like a 100% acrylic latex caulk, but have silicone added to them for water resistance and additional flexibility and durability. They often come in a wide range of colors including clear, and are paintable. Latex with silicone caulks are easy to work with, and clean up is painless too.
Use latex with silicone caulk for: General purpose, indoors and outdoors
Adheres to:
- Wood
- Brick
- Drywall
- Metal
- Painted surfaces
- Glass
- Plaster
- Most common building materials
Butyl
Butyl (or butyl rubber) caulks are inexpensive and offer superior adhesion qualities, but they can be challenging to work with as the rubber makes the product stringy. Butyl can make a nice, smooth caulk bead very difficult to achieve. For this reason, and its excellent weather resistance, butyl is often used to seal gutters, chimney flashings, and other exterior joints that are not easily seen.
Use butyl caulk for: Outside surfaces like gutter joints and metal-to-masonry joints
Adheres to:
- Wood
- Metal
- Concrete/masonry substrates
- Glass
It can be pretty confusing to stand in the caulking section and find you’re facing dozens of options. I hope this information sheds light on the variety of caulks and their common uses. Pick a caulk designed to adhere to the substrates you’re working between. From there, remember to caulk between clean surfaces and to read the fine print about application temperatures, color, and techniques.
