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Caulk Exterior Walls

Materials Cost: 1
Difficulty Level: 1

Introduction

Replace cracked or missing caulk along windows, doors, and trim on exterior walls to prevent water intrusion into walls.

Why

Exterior caulking prevents water damage and ensures that a home is well-sealed from the outdoor environment. Over time, the bond between caulking and siding and trim weakens, allowing the caulk to crack or peel away. Replacing old, cracked caulking will help stop water leaks; can prevent the air leaks that contribute drafts and unwanted heat loss or heat gain, and can even help to keep out bugs.

What You'll Need

  • Caulking gun
  • Utility knife
  • Razor scraper
  • Masking tape
  • Rubbing alcohol
  • Rags
  • Gloves

1. Locate exterior caulking.

The best time to caulk is during the summer, or late spring or early fall, when temperatures are still warm and the caulk is softer and easier to work with. Just before you paint the exterior of the home is another ideal time to check and fix caulk. If you are worried about your caulking skills, practice in an inconspicuous location on your home, such as along the back or side. You can also practice using the caulk gun on a piece of cardboard to “get the hang” of the process.

Exterior caulking is commonly located in the following areas: around windows, around doors, along trim, between dissimilar building materials, along eaves and overhangs, around exterior light fixtures and other wall penetrations, and around vents. If the exterior caulking is cracked, such as in Figure 1, it should be replaced.

Figure 1. The exterior caulking around this window is clearly cracked and peeling, indicating that the caulking is no longer performing well and should be replaced (Source: PNNL).

2. Remove old caulk.

The old caulk should be removed prior to installing the new caulk. Use a utility knife to cut along both edges of the old caulk (Figure 2). Caulk is easier to remove when warm, so it may be desirable to complete this project in the summer or late spring. Or, a hair dryer or low-temperature heat gun can be used to soften the caulk.

Figure 2. To remove old exterior caulk, use a utility knife (left) or a putty knife (right) to cut along both edges. (Source: RONA, inc.).

After the seams have been cut, use pliers or your fingers to pull off the strips of caulk (Figure 3). Older, cracked caulk may have to be removed in small pieces. Remove all of the old exterior caulk prior to moving to the next step.

Figure 3. Pull off strips of old caulk using pliers or your fingers. Remove residual caulk using a razor scraper. (Source: RONA, inc.).

3. Clean caulking areas.

Caulk adheres best to a clean and dry seam. If there is residual old caulk remaining after Step 2, use a razor scraper to chip off the remnants. In hard-to-reach areas, a bristled brush can help to loosen old caulk. 

Once the old caulk is completely scraped off, use a dry rag or a soft brush to remove the debris from the area. 

Put on rubber gloves and clean the debris-free seams with rubbing alcohol and a clean rag (Figure 4).

Figure 4. Clean exterior seams with rubbing alcohol prior to applying caulk (Source: RONA, inc.).

4. Prepare the seams for caulking (optional).

Although optional, painter’s tape can be applied to both sides of the seams prior to caulking to ensure straight lines and an even, attractive appearance (Figure 5).

Figure 5. Painter’s tape was applied to both sides of this seam before caulking (Source: RONA, inc.).

5. Apply caulking.

Before starting, use a piece of scrap cardboard to test the caulk gun and become comfortable with using it.

Squeeze the handle of the caulking gun lightly, to apply a thin line of caulk to the seam. 

Using a gloved finger or a piece of plastic with a round edge (such as a plastic spoon), gently press in and smooth the caulk. This pushes the caulk into the seam and creates a smooth appearance (Figure 6). You can clean up any residue that got onto siding, trim, or your tools with a rag dipped in isopropyl (rubbing) alcohol or mineral spirits.

Figure 6. Use a gloved finger or a piece of plastic with a round edge (such as a plastic spoon) to “tool” caulk. This pushes the caulk into the seam and creates a smooth appearance (Source: RONA, inc.).

Additional Info

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Disclaimer

This content is a work created with funding provided by the United States Department of Energy under Contract no DE-AC05-076RL01830 for the operation of Pacific Northwest National Laboratory. The information and guidance provided by Pacific Northwest National Laboratory (PNNL) in the content are intended solely for educational purposes only and do not constitute formal training or certification. It is provided with the explicit understanding that neither the United States Government nor the United States Department of Energy, nor the Contractor, nor any or their employees, nor any jurisdiction or organization that has cooperated in the development of these materials, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness or any information, apparatus, product, software, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or Battelle Memorial Institute. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Viewers assumes full responsibility for all actions that they may take from information provided in this content including ensuring the safety, code compliance, and proper functionality of any products they choose to install. Installation and use of such products should be performed in accordance with local regulations and manufacturer instructions.