Where not to caulk around windows

Where not to caulk around windows

Caulking around drip edges, weep holes, window trims, moving parts, or over old caulking can lead to moisture damage, mold, mildew, cracking and warping, or failure of the window seals.

Windows and window frames are designed with water management in mind to prevent damage from moisture infiltration. If you caulk over these areas and compromise these features, it can lead to damages costing you thousands of dollars.

In this article, we have outlined where not to caulk around your window and the type of caulk best for interior and exterior windows. We also walk you through how to use silicone caulk around a window appropriately. 

Don’t caulk the drip edge of a window

Caulking around a window's drip edge interferes with the window's ability to shed water, leading to water buildup and causing it to seep into the window frame. Over time, the water buildup will lead to rot, rust, or mold growth around the window.

What is a drip edge on a window?

The drip edge is the small overhang at the top or bottom of your window frame. It allows water to run off and not get trapped around the window. The drip edge is essential for preventing water from seeping into the frame, which can lead to wood rot, metal rusting, and mold from the trapped moisture.

Where not to recaulk your windows

When too much caulk is applied or placed over window areas that do not need caulking (such as the weep holes, window sashes, etc.), water has nowhere to escape and accumulates behind the window frame. 

Weep holes and drainage channels

Weep holes are small openings designed to let water escape from inside the window frame while drainage channels are grooves or pathways built into the frame to direct water away. Caulking over them will trap water, leading to rot, mold, and potential structural damage. Instead, ensure the weep holes and drainage channels are clear of debris and functioning properly.

Window sashes

The sash is the movable part of the window that holds the glass. Applying caulk here can seal the window shut, preventing it from opening or closing. If there’s air leakage, replacing or repairing the weatherstripping or sash seal is a better option.

Moving parts of the window

Moving parts, such as sliders, pivots, or cranks, need to remain mobile for the window to function. Caulking them will interfere with their operation and cause permanent damage. Instead of caulk, inspect and replace any worn gaskets or seals. Consider using silicone-based lubricant for windows with metal tracks to improve their movement.

Over the drip edge

The drip edge directs water away from the window, wall, and roof to prevent moisture infiltration into the structure. Applying caulk over the drip edge traps water behind it, which could lead to water damage, rot, or even ice dams in colder climates.

Around the exterior trim 

The trim around a window is designed to give the window a finished, polished look. However, applying silicone or polyurethane caulk incorrectly to this area can trap moisture behind the trim, preventing proper air circulation and leading to wood rot and mold growth. 

On top of old caulk

Recaulking directly over old, cracked, or deteriorating silicone caulk will not bond properly. Additionally, the moisture trapped beneath the old caulk could continue to cause damage, which the new caulk will not address. 

Remove the old caulk entirely before applying the new caulk. This will help create a more effective, durable seal that will last longer.

Caulking around exterior windows

What kind of caulk should you use for exterior windows?

The best caulk for exterior windows is silicone or polyurethane. Polyurethane caulk is best for areas with movement or expansion. It’s more versatile, adheres well to various materials, and can be painted. Silicone caulk is more flexible, weatherproof, and can withstand direct sunlight. However, it cannot be painted.

Gather everything you need

Before you begin, gather all your tools and materials so that everything is within reach. This includes your silicone or polyurethane caulk, caulking gun, smoothing tool (optional), utility knife or box cutter, painter's tape, clean cloth or paper towels, and cleaning supplies (soap, water, rubbing alcohol, or acetone).

Clean the surface

Thoroughly clean the window frame and surrounding area to remove dirt, dust, and old caulk. For dirt and dust, use soap and water or a solvent like rubbing alcohol to wipe down the surface. If there’s old, cracked, or peeling caulk, use a utility knife or box cutter to scrape it off carefully. 

Cleaning ensures that the new caulk will bond properly to the surface. Dirt, oils, or moisture can prevent caulk from sticking well, resulting in gaps, which can lead to drafts or water leaks. Likewise, if you leave remnants of the old caulk, the new caulk won’t properly form a solid bond with the surface.

Tape the edges

If you want a clean, straight line, apply painter’s tape along the edge of the window frame where it meets the wall or trim, creating a neat boundary around the frame. This ensures that the caulk stays neatly along the gap between the window frame and the wall without spreading onto the wall or trim itself. It also makes cleanup easier by keeping the caulk where it’s supposed to be.

Cut the caulk tube tip

Use a utility knife to cut the caulk tube's tip at a 45-degree angle. Start with a small opening; you can always enlarge it if necessary. The hole size should match the width of the gap you are sealing, typically around 1/4 inch. If the caulk tube has a seal inside, puncture it with a long nail or the tip of the caulk gun.

Load the caulk gun

Insert the tube into the caulk gun and press the release trigger to secure it. Ensure the plunger is firmly against the base of the caulk tube.

Apply the caulk

Starting at one corner, hold the gun at a 45-degree angle to the surface and apply a steady bead of caulk along the gap between the window frame and the wall or trim. Move the gun in a continuous, smooth motion. Avoid starting and stopping to prevent uneven coverage or gaps.

Smooth the caulk bead

Immediately after application, smooth the caulk bead using a caulk smoothing tool or your damp finger (your finger dipped in water). This ensures a uniform seal and also helps to remove excess caulk, giving it a clean, professional look.

Remove painter’s tape

Carefully peel off the painter’s tape while the caulk is still wet. If you wait too long and the caulk dries, the tape could pull off parts of the caulk and leave a messy edge.

Use rubbing alcohol or acetone to remove the caulk that has dried on the surfaces you didn’t intend to caulk.

Let the caulk cure

Allow the caulk to fully cure per the manufacturer’s instructions. Typically, it takes 24 hours before exposing it to water or heavy use. This ensures it forms a strong and durable bond. In addition, avoid touching or painting the caulk until it’s fully cured.

How to caulk windows inside a house

Gather the proper caulk and other materials

You will need acrylic latex or silicone latex caulk (if you're sealing high-humidity areas like bathrooms, kitchens, or laundry rooms).

Clean the window frame

Clean the window frame with soap and water or rubbing alcohol to remove dust, dirt, and oils. If there's an old caulk, use a scraper to remove it.

Application

Cut a small opening at the tip of the caulk tube at a 45-degree angle. Apply the caulk slowly and carefully, as interior windows typically have narrower gaps around the frame.

Smoothing the caulk

After applying the caulk, smooth it out using a caulk smoothing tool or a damp cloth to ensure a neat finish.

Cleaning up

Clean up any excess caulk with a damp cloth before it dries. This step is easier compared to exterior projects because interior caulks (latex-based) are water-soluble before curing.

The importance of where not to caulk around windows

Knowing where not to caulk around windows is just as important as knowing where to apply caulk. Improper caulking can lead to trapped moisture and water buildup, poor ventilation, warping of the window frame, and can restrict the window movement.

You can do most caulking projects. However, it comes with certain risks, especially if you're uncomfortable with home projects and handling certain tools. If so, it's best to call in the professionals.

You can either hire your local handyman to recaulk your window or use a platform like Angi. We recommend Angi because it offers a large database of vetted and skilled handymen in your local area. In addition, the platform features reviews and ratings from real customers, giving you valuable insights into the quality of work you can expect and if a handyman specializes in a particular type of project.