How to Caulk Windows?

After receiving the windows and doors from the suppliers, it’s time to install them. Once the window or door is in place, there will be a gap that needs to be filled. What material should we use to fill the gap, and what is the best way to ensure a professional finish?

Generally speaking, caulk and silicon are the two most popular choices to fill the gap. Today, we will learn how to caulk windows first.

How to Choose Caulk?

Caulks are similar to door and window sealants in that various grades of products are available. To cut costs, some manufacturers add impurities such as powder or oil to polyurethane foam, which can result in poor-quality caulk. These caulks may be challenging to cure, produce more hollow drums, have a soft texture, and have a shorter lifespan.

1. Choose a Reputable Brand

It can be challenging for consumers to determine the quality of caulk. Choosing a reputable brand or model is the best way to ensure you purchase a quality product. Some well-known blowing agent brands include Soudal, SELENA, Sunrise, Feng Jing, GNS, Tianyuan, Three Trees, Mei Sheng, Yusheng, and Ao Feng.

2. Choose a Higher Fire Rating

One way to determine the quality of a foaming agent is to look at its fire rating, typically classified as A or B. A higher fire rating, such as A1 or A2/A3, is better than a lower rating, such as B1. Choosing a caulk with a rating of at least B2 is recommended, but if budget allows, selecting an A-class caulk is preferable.

3. Choose a Higher Expansion Coefficient

Another way to determine the quality of caulk is to examine its expansion coefficient, which typically ranges from 70-80. The higher the value, the faster the expansion rate, which is considered a small detail but can help recognize the quality of the caulk.

how to choose caulk

How to Caulk Windows?

Foam caulking is a simple and effective solution for installing windows and doors. After positioning the door or window frame on the wall, apply a circle of caulk directly around the gap in the window frame. Allow the foam to harden before proceeding with the next steps of installation.

For best results, it is essential to be meticulous during the construction process.

1. Clean up the Dust

Before filling the caulk, use a tool such as a brush to clean up any debris or dust on the hole surface. Failure to do so may result in incomplete filling and insufficient bonding.

how to caulk windows

2. Wet the Gap

Additionally, it is recommended to wet the gap with water before filling the caulk, especially in dry weather conditions. This will help the foam expand and clear any remaining dust.

how to caulk windows

3. Shake the Caulk for Even Mixing

Finally, shake the bottle of caulk before use to ensure even mixing.

When using caulk during construction, it’s best to apply it along the edge of the window frame. This ensures that the construction is adequate and the later effect is more guaranteed. Caulk should be applied vertically from the bottom to the top to avoid any lack of caulk fall.

4. Check for Gaps

After the initial expansion of the caulk, which typically takes around 5-10 minutes, it is vital to check for any gaps. If there are any gaps, they should be filled to avoid a lack of caulk, which can impact the effectiveness of the later stages.

5. Compact the Caulk

If there are no gaps, it is best to compact the caulk using a scraper or other tool, ensuring the gap is filled. This will help to ensure that the window frames and wall connections are entirely free of any dead ends, eliminating the need for future work or the possibility of accidentally destroying the foam.

6. Waterproofing Test

Once the caulk has fully expanded, use a spray can for a waterproofing test.

how to caulk windows

7. Maintenance Tips

To ensure your caulked windows stay in good condition, follow these maintenance tips:

  • Regularly inspect caulked areas for signs of wear or damage, and reapply caulk as needed to maintain a tight seal.
  • Consider caulking windows annually or as needed to prevent drafts and energy loss.
  • In addition to caulking, explore other ways to improve the energy efficiency of your windows, such as installing weatherstripping or storm windows.


Caulking your windows is a simple yet effective way to improve your home’s energy efficiency and comfort. Following the steps outlined in this guide, you can master the art of caulking and enjoy a snug, draft-free living space year-round. Don’t neglect this essential home maintenance task—your wallet and comfort will thank you!





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