Why Does Caulk Crack Around Windows?

Caulking around windows helps reduce your energy bills by preventing hot or cold air from escaping and external air from entering your home. If the caulking around your windows is cracked, it won’t be as efficient. So, why does caulk crack around windows? 

Caulk cracks around windows because of extreme temperature fluctuations, humidity, and condensation. Other reasons include incorrectly applied caulk and if it has reached the end of its lifespan. You can fix the cracked caulk by replacing the cracked section or the entire caulk bead. 

In this article, I’ll explore why you might find cracked caulk around your windows. I’ll also discuss how to fix it and prevent it from happening in the future. 

caulk crack around windows

Why Your Caulk Is Cracking Around Windows

Temperature Fluctuations

Window caulk can experience extreme temperature changes because there’s often an extreme difference between the temperature inside a room and the weather outside. 

Sudden temperature changes can cause the caulk to expand and subsequently shrink, potentially resulting in cracks. If you live in an area with an extremely hot or cold climate, it’s best to buy caulk that can withstand extreme temperature fluctuations. 

The Caulk Is Too Old

Window caulk doesn’t last forever, and its lifespan ranges from 5 to 25 years. This depends on the type and quality of the caulk used. 

For example, acrylic latex caulk is inexpensive, but you’ll need to replace it approximately every 5 years as it has a short lifespan. Siliconized latex caulk will last slightly longer, but pure silicone caulk has a typical lifespan of 25 years. 

Once the caulk has reached its expected lifespan, it can show signs of wear and tear, such as cracking. 

Humidity and Condensation

If your window caulk is not pure silicone (which is waterproof), humidity and condensation can cause it to swell and then crack when the moisture dries. 

Condensation around windows typically happens on bathroom or kitchen windows and if you live in a high-humidity area. 

Window caulk can also crack if it’s exposed to high moisture levels before it’s fully cured.

Incorrectly Applied Caulk

Incorrectly applying caulk can lead to premature cracking. If you apply too much caulk, it may not cure properly, leading to cracking. 

After applying caulk, you should scrape off the excess to achieve a neat finish. However, if you are too vigorous when removing the extra caulk, you might remove too much, and the caulk layer will be too thin. This can cause it to crack. 

The room temperature when applying caulk can also affect its tendency to crack. Most manufacturers recommend applying caulk at temperatures above 40°F (4°C), but some caulk varieties can be applied at colder temperatures. If the room temperature is too cold, the caulk may shrink and crack as it cures due to the weaker chemical bonds. 

Silicone caulk is suitable for application in colder weather

2 Easy Fixes for Cracked Caulking Around Windows

How you fix cracked caulking depends on the severity of the problem. If only one area is cracked, you can recaulk that section. However, more extensive cracks will require replacing the caulk. 

1. Recaulk the Cracked Section

Follow these steps to replace a cracked section of caulk: 

  1. Apply caulk remover to the affected area only and wait for 10 minutes. Mostenbocker’s Sealant Remover Spray from Amazon is fast-acting and will weaken the cracked caulk within 10 minutes. 
  1. Remove the cracked caulk with a sharp knife, and ensure that the area is clean and dust-free and no caulk remains. 
  2. Place your caulk tube in the caulking gun and apply the caulk in a continuous bead.
  3. Wipe off the excess with a putty knife, and allow the caulk to dry thoroughly before touching it. 

2. Replace the Caulk

If your window caulking is extensively cracked, here’s how to replace it: 

  1. Using a sharp knife, gently cut the cracked caulking and peel it off.
  2. Remove any dust and debris and clean it with a damp cloth and gentle detergent. 
  3. Allow the area to dry completely. 
  4. Load your caulking gun with the caulk tube.
  5. Cut off the top of the caulk tube at 45 degrees. 
  6. Extrude a steady caulk bead around the window.
  7. Use a putty knife to remove excess caulk and create a neat finish. 
  8. Leave the caulk to cure, and don’t expose it to water until it’s fully cured.

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Ways To Prevent Caulk Cracking Around Windows

1. Use the Correct Application Method

Before applying the caulk, ensure all the old caulk has been removed. When you apply new over old caulk, the fresh layer will not cure completely and will begin to crack. 

When caulking, apply a steady bead around the window, being careful not to apply too much. If the caulk layer is too thick, it may form air bubbles and become susceptible to cracking. 

If you notice any excess caulk, remove it with a putty knife or gloved finger. 

2. Maintain the Caulk and Recaulk When Necessary

  • Clean the caulk regularly: Keep the caulk clean so you don’t need to resort to harsh chemicals to remove stubborn build-up. Strong chemicals can strip the caulk and cause it to dry further, leading to cracking.
  • Recaulk when necessary: If you find that some parts of the caulk are damaged, it’s best to recaulk before the problem spreads. This can save you a lot of work later on.

3. Use a Backer Rod

Backer rods are made of flexible foam, and you can install them before caulking. They offer various benefits in preventing caulk from cracking: 

  • They help increase the caulk’s elasticity. Backer rods are also called bond breakers because they allow the caulk to bond with the sides of the wall only. Since the caulk doesn’t collect in the joint, it improves elasticity.
  • Backer rods provide additional insulation. A backer rod seals tiny holes around the window and helps prevent moisture from contacting the caulk. This can prevent or delay cracking.
  • They help you apply the correct amount of caulk. Because backer rods help prevent caulk from collecting in the joint, you’re more likely to apply an even strip. Evenly-applied caulk is less likely to crack. 

Final Thoughts

It’s normal for caulk to crack around windows when it has reached the end of its lifespan. If your window caulk is cracked in only one section, you can recaulk it. However, extensively cracked window caulk requires replacement. 

You can prevent your window caulk from cracking by: 

  • Using the correct application method
  • Maintaining and cleaning your caulk regularly
  • Using a backer rod