A Professional's Guide to Caulking

Caulk adds a finished look and an extra layer of protection to every home and construction project. However, DIYers and contractors face several choices, from type to application techniques, that can make or (literally) break their projects. 

With so many types of caulk available–silicone, acrylic, urethane, clear, tinted—it can be challenging to know which one to choose and how to use it correctly. The wrong type or improper application can lead to cracking, peeling, or unsightly gaps.

Thankfully, after 25 years of industry experience painting and caulking thousands of homes and buildings, the Roe Painting team has learned the best ways to help you achieve a smooth, long-lasting finish on your next project. 

In this article, we’ll share our expertise on:

• What is caulk, and why is it so important?
• Which caulk you should use for your project
• Common do’s and don’ts for longer-lasting results

What Is Caulk, and Why Is It So Important?

Caulk is a flexible, semi-liquid material used to seal joints and gaps between two surfaces, keeping air and moisture out. Applied with a caulking gun, it helps create a smooth transition between different materials. For painting projects, caulk seamlessly connects wood trim and drywall for a polished look. 

It also prevents water damage for exterior projects by sealing cracks and gaps in the siding and around door and window frames. 

When appropriately applied, caulk prevents water from sneaking into gaps, protecting your home from costly repairs caused by moisture damage and mold. However, using the wrong caulk or applying it incorrectly can lead to premature failure, resulting in cracking and shrinking. 

Which Caulk You Should Use for Your Project

Like with many materials, “you get what you pay for” applies to caulk. Inexpensive caulks might be tempting, especially if you are working on a tight budget, but they usually fall short in performance. Often used in production painting or new construction, these cheaper caulks may crack or lose flexibility over time, especially in high-stress conditions. 

Different types of caulk are designed for specific environments:

• Acrylic Caulk: Ideal for interior trim or gaps between drywall and baseboards. It’s paintable and easy to work with, but not suitable for high-moisture areas. 
• Silicone Caulk: Perfect for bathrooms, kitchens, and windows because it’s water-resistant and flexible, though it cannot be painted. 
• Urethane Caulk: Excellent for exterior applications thanks to its durability and flexibility under extreme weather conditions. 
• Hybrid Caulk: Combines silicone and polyurethane properties for flexibility, durability, and paintability. 

There’s also some common terminology you’ll find when looking at different types of caulk:

• Curing Time: The time it takes for the caulk to harden and reach maximum strength and flexibility.
• Paintable vs. Non-Paintable: Acrylic-based caulks are best for painting, while silicone-based caulks cannot be painted. 
• Shrinkage: The reduction in size as caulk dries, which may affect its ability to maintain a seal.
• Adhesion: The ability of caulk to stick to the surface and create a lasting seal. Acrylic caulk has a moderate adhesion level, making it easy to apply, but it doesn't work on slick surfaces. Silicone, urethane, and hybrid caulk have high to very high levels of adhesion. 

Best Caulk for Interior Painting Projects: 

For interior paint jobs, we recommend investing in medium-grade acrylic or siliconized acrylic caulk, such as Sherwin Williams 950A Siliconized Acrylic Latex Caulk. These typically cost between $2.50 and $3.00 per tube and offer the flexibility and durability needed for small gaps between trim and drywall or woodwork. They are easy to work with, paintable, and won’t shrink significantly as they dry.

Best Caulk for Exterior Painting Projects: 

Exterior surfaces experience much more wear and tear due to weather changes, sun exposure, and materials' natural expansion and contraction. High-quality urethane or urethane-fortified caulks, such as Pro Stretch by Tower Sealant sold through Rodda Paints, are ideal for these jobs. They run about $5 per tube.

They offer superior elongation properties, which means they can stretch and flex with the movement of the materials without cracking or peeling. These caulks are also resistant to UV rays and extreme weather conditions, making them a must for outdoor applications.

Caulking Do’s & Don’ts for Long-Lasting Results

Even with the right materials, proper caulking takes skill and experience. Unfortunately, cutting corners by using cheap caulk or inexperienced applicators can lead to peeling, cracking, and early failure. Below are some key do’s and don’ts that professionals follow to ensure high-quality results—and what to watch out for when hiring a contractor.

Caulking Do's

1. Choose the Right Caulk for the Job: Different caulks are designed for different purposes. For example, the caulk you use to seal bathtubs and sinks is designed to work well in wet environments, but isn’t strong enough to work outdoors on siding and trim. Read labels carefully to ensure that the caulk you choose is suitable for the condition and purpose of your particular project. 
2. Thoroughly Prepare Surfaces Before Application. Proper surface preparation is key. If present, remove all cracked or failing caulk before moving on to clearing all dust, dirt, and moisture. This gives the new caulk a clean place to adhere. Skipping this step could affect the application of the caulk. 
3. Apply Caulk Only to Small Gaps: Caulk is meant to fill small gaps and joints–⅛” or less. For larger gaps, you’ll need to use another filler, like backer rod or expandable foam, before applying caulk.
4. Smooth the Caulk Immediately: Once the caulk is applied, smooth it out with your finger or a damp rag to ensure a seamless transition between surfaces. This not only improves the appearance but also helps the caulk adhere better and last longer. 

Caulking Don’ts

1. Don’t Use Cheap Caulk: Cheaper caulks often shrink as they dry, crack over time, or lose flexibility, especially in extreme weather conditions. This can lead to gaps reappearing and water intrusion. Invest in a good-quality caulk for any job, particularly for exterior projects where durability is key. 
2. Don’t Use Caulk to Fill Nail Holes: Caulk is not designed to fill small, localized holes made by nails and screws. It tends to shrink as it dries, which means the holes will still be visible after painting. Instead, use a non-shrink wood putty or another filler specifically designed for nail holes. 
3. Don’t Leave Paintable Caulk Unpainted: Since caulk is flexible (remains soft), it can collect dirt over time. Even clear caulk will become dingy if exposed to dust and grime. For the best results, always paint over the caulk to protect it and ensure a clean, professional look.
4. Avoid Clear Silicone for Paint Jobs: Clear silicone caulks are often non-paintable, meaning the paint will not adhere well and will eventually peel off. If you are looking for a paintable caulk with the flexibility of silicone, opt for urethane-base caulks, which offer similar durability but can be painted.

The Right Caulk for a Long-Lasting Finish

Caulking plays a crucial role in protecting your home from the elements and maintaining its appearance. DIY fixes might seem simple, but even small mistakes can lead to larger issues like water damage, mold, and costly repairs. A successful caulking job comes down to using the right material for the right job and ensuring a proper application for a seamless, long-lasting finish. 

If you’re unsure whether your caulk needs professional attention or just routine maintenance, read our blog “How to Avoid a Painful Contracting Experience” to learn how partnering with expert contractors can make all the difference. 

Don’t wait for small gaps to become big problems–we’re here to guide you every step of the way!