How to Caulk Plywood Siding

Lead Image
  • 1-2 hours
  • Beginner
  • 50-100
What You'll Need
Caulk gun
Chisel or putty knife
Rubbing alcohol
Utility knife
Foam backer rod
Soapy water

When installing plywood siding, properly caulking the seams between the siding pieces is a very important part of the installation. Caulking is used to seal the seams between the plywood siding pieces and keep out moisture that could damage the interior sides of the siding and even the studs in the walls. It is important to know how to properly caulk plywood siding during the installation. Fortunately, this easy to follow how-to guide will help you to learn how to caulk plywood siding like a pro. Let's get started.

Step 1 - Choose the Right Caulk

Before you begin caulking your plywood siding, you want to make sure that you choose the right type of caulk. Choose a caulk that closely matches the stain or paint color that you will be using on your plywood siding. Also, make sure to choose a high-quality silicone-based exterior caulk. Although these types of caulks are a little more expensive, they hold up much better to the elements and are usually much cheaper over the long run.

Step 2 - Choose the Right Time

You may also want to choose the right time of day to caulk your plywood siding. It is best to apply caulk to plywood siding when it is between 50 and 70 degrees Fahrenheit. If the weather is too cold, the caulk could freeze. On the other hand, if the weather is too hot, the caulk may dry out too quickly and not create a good seal between the siding pieces.

Step 3 - Remove Old Caulk or Sealant if Needed

If you are caulking a previously installed piece of siding, you'll first need to remove the old caulk or sealant from the seams. To do this, run a utility knife or scraper down the seams to loosen up the old caulk or sealant. Then carefully scrape it away and use the knife or scraper to clean up the edges.

Step 4 - Insert Foam Backer Rod if Needed

If the gap between the pieces of plywood siding is more than about 1/2 inch, you may want to use a foam backer rod to fill the gap. Use the utility knife to cut a piece of foam backer rod and stuff it into the seam between the pieces of plywood siding. Make sure that the foam backer rod does not protrude above the surface of the siding.

Step 5 - Cut Tip on Caulk

Use your utility knife to cut the tip of the caulk tube applicator at a 45-degree angle. This will ensure a smooth flow of caulk when using the caulking gun.

Step 6 - Caulk the Siding

After you insert the tube of caulk into the caulk gun, you can begin caulking the seams. Slowly run a bead of caulk over the seams between the plywood siding. Don't worry too much if you make a mistake, but try to move the caulk gun along the seam as smoothly as possible. Avoid starting and stopping as this will create build up or ridges in the caulk.

Step 7 - Use Spoon to Smooth Caulk

Fill a small container with soapy water and then dip the spoon into it. Take the spoon and use it to smooth out the seams between the plywood siding. Do this before the caulk hardens or sets.