Window Caulking: When to Recaulk, How to Do It, and Which Sealant to Use

Window caulking is due when the bead is cracked, loose, or missing, and the new bead seals the joint between the frame and the wall only after the old bead is gone and the drainage path stays open. Caulking around windows means sealing the perimeter joint, not applying a line of sealant across the glass. A sealed unit is bonded at the factory, and homeowners do not caulk the glass.

The exterior bead and the interior bead are different materials. Outside, use 100% silicone, or polyurethane where the joint meets masonry, brick, or stucco. Inside, use paintable acrylic latex on trim that will be painted, and siliconized acrylic in a humid room. The cartridge is what you read for paintability, for the temperature it accepts, and for whether cleanup is water or solvent.

Seal the top and the sides, and leave the bottom exterior joint under the sill and the weep holes open so water can leave the frame. Remove the failed bead, clean and dry the joint, and tool the new bead while it is wet. A sound bead still will not repair rot, a window that does not fit the opening, or fog between the panes.

Key Takeaways

• Recaulk when the bead is cracked, pulled away, missing, chalky, or hard, or when a draft sits at the frame with the sash locked.
• The exterior bead is 100% silicone, or polyurethane on masonry, brick, or stucco. The interior bead is paintable acrylic latex, or siliconized acrylic in a humid room.
• Seal the top and the sides. Leave the bottom exterior joint under the sill, and the weep holes, open.
• Remove the old bead, clean and dry the joint, and tool the new bead while it is wet. A gap wider than 6 mm needs foam backer rod first.
• A bead will not repair rot, a window that does not fit the opening, a leak that continues after a sound bead, or fog between the panes.

When Should You Recaulk a Window?

Recaulk a window when the bead has failed, and judge that by the bead, not by a year count. A bead that is cracked, pulled away, missing, chalky, or hard is finished, and so is a draft you can feel at the perimeter while the sash is closed and locked. Water stains on the inside trim mean water has already been getting past the joint. Checking those signs is how to recaulk windows, and a bead that is still soft, stuck to both sides, and sitting on a dry frame can stay.

Check the bead with the sash closed and locked, on a day when the joint is dry. Look at the corners first, because a bead usually cracks there before the long runs let go. A locked sash that still drafts after the bead looks intact can be the window, not the sealant, when the frame has shifted or the opening no longer matches the unit. A sun-exposed wall hardens a bead, so look there for the same cracks and pull-away, without giving that wall a shorter year count than a shaded wall.

Walk the frame before you buy a tube, and match the bead in front of you to the job. A crack at a corner is a different job from a bead that has only collected dirt. Stains low on the trim mean you should look outside before you seal anything on the inside. If the bead is intact, soft, and stuck on both sides, you are not recaulking yet.

• Cracked or missing. The joint is open, so air and water can get in.
• Pulled away on one side. The bead no longer sticks to both the frame and the wall.
• Chalky or hard. It no longer flexes when the frame moves, so it has to come off.
• Stains on the inside trim. Water has already passed the exterior joint, and the stain is the record.

Do not lay a new bead over a bead that has pulled away, because the new material bonds to the failure and comes off with it. Do not caulk a damp or dusty joint and expect it to hold. Don't close a weep slot just because it looks like a gap that should be filled. A sound, soft bead on a dry frame is not a job, and another tube will not make it better.

Which Sealant Goes Inside, and Which Goes Outside?

Use silicone or polyurethane outside, and use paintable acrylic latex or siliconized acrylic inside. A window sealant has to match the side of the wall it sits on, because an interior tube won't survive a Canadian winter on the exterior, and pure silicone will not take paint on trim. Read the cartridge for the place, for paintability, and for whether cleanup is water or solvent. Window caulk is the tube in your hand, and that label is the instruction.

Four sealant types cover the joints a homeowner actually meets on a window. The grid holds the match, and the lines under it hold the limits, including the interior tube that does not belong outside. Butyl rubber is not in the grid because it is a flashing material, not the frame-to-wall bead. Nothing in the grid is a brand, and nothing in it is a lifespan.

Butyl rubber is for a metal flashing joint next to the window, and it is the wrong bead for the frame-to-wall joint and for interior trim. Acrylic latex is the wrong exterior bead in a Canadian winter, so keep it on interior trim that will be painted. Pure silicone is the wrong choice on trim someone needs to paint, because paint will not stick to it. Use polyurethane on the exterior where the joint is masonry, brick, or stucco, and use 100% silicone as the exterior bead on other cladding.

How Do You Caulk the Exterior Without Trapping Water?

Exterior window caulking seals the top and sides while leaving the bottom drainage path and weep holes open. Done wrong, exterior window caulking closes the joint under the sill or packs the weep slots, and then the frame holds water. The bead still has to stick to both sides of the joint, so the old material comes off before the new bead goes on. Caulking exterior windows in the cold is a separate failure, because the compound goes stiff and will not tool into the joint.

Do not caulk where the temperature is below 5°C , because the compound gets stiff and will not tool. The same guidance says a gap greater than 6 mm needs foam backer rod or foam rope before the bead goes in, so the sealant skins over a support instead of filling an empty void. It also says one standard tube makes a bead about 6 mm wide and 7.6 m (25 ft) long, which is a planning figure, not a promise that the bead can bridge a wide joint. Prefer a dry day, and follow the cartridge for rain and for cure rather than a drying time copied from another job.

The weep holes are the small slots near the bottom of the exterior frame, and they let water that enters the frame drain outward. The joint under the exterior sill, where the sill meets the wall below, is the other part of that path, so seal the top, the sides, and the upper edge where the sill meets the wall, and stop before that lower joint. On an install by Canadian Choice Windows & Doors™, the perimeter is sealed, and those weep paths are left open, and the same rule applies when you recaulk a window that is already in the house. Closing the bottom joint or the slots holds water in the frame, and that water moves into the wall.

"When a homeowner has sealed the joint under the exterior sill, we open the sash and find the frame sitting in water. The weep slots tell the same story when they are packed shut, because the water that entered the frame has no way out. Those two paths have to stay open, or the new bead holds the water against the wall," says Tony Wong, Project Manager, Canadian Choice Windows & Doors™.

What Is Different About Interior Window Caulking?

Interior window caulking is a finish and a minor air seal, not the weather seal. Use paintable acrylic latex where the trim will be painted, and use siliconized acrylic in a humid room such as a bathroom or a kitchen. Do not use pure silicone on trim someone needs to paint, because the paint will not bond. Window caulking interior follows that same split: the bead hides the joint and slows a small air leak, and it does not keep rain out of the wall.

Run the interior bead where the trim meets the wall and where the stool meets the frame, and keep it off the glass. A small gap at the casing is a finish joint, and acrylic latex is there so you can paint it to match the trim. A humid room needs the silicone version so the bead tolerates moisture on the room side without pretending to be the weather seal. If the draft is strong with the sash locked and the interior bead looks perfect, the leak is not an interior paint line.

Moisture on the room-side glass is window condensation from humidity in the house, not a failed bead, and it is not a covered defect. Fog between the panes is a sealed-unit issue, not a caulk job, and on a window installed by Canadian Choice Windows & Doors™, it is covered under the 25-year transferable window warranty . *See warranty guide for details and explanations. The bead itself is not covered for that term.

How to Caulk a Window, Step by Step

Caulking windows follows a specific order, and skipping removal is why the new bead lets go. A dry joint with the old material gone is how to caulk windows, not a fresh tube laid over a cracked line. Hold a thin sheet of paper at the frame and move it slowly: if the paper moves, air is leaking at that spot, which tells you where to work. Follow the cartridge for cure and for rain, and do not copy a drying time from a different tube.

1. Cut the old bead out. That cut is how to remove old window caulking: lift the failed bead with a utility knife, take the split and dried compound with it, and leave both sides of the joint bare.
2. Clean and dry the joint. Brush off dirt and loose paint. A damp or dusty surface will not hold the new bead, so wait until the joint is dry.
3. Support a wide gap. If the gap is greater than 6 mm, press foam backer rod or foam rope into the joint so the bead has something to bridge. The rod is the filler. The bead is the seal.
4. Cut the nozzle on an angle. Start with a small opening. You can cut more off the tip, and you cannot put the tip back on.
5. Apply a continuous bead. Keep the gun moving so the bead sticks to both sides of the joint, and ease off the pressure at the end so the tube does not dump a blob.
6. Tool the bead while it is wet. For a water-based or silicone compound, finish it with a finger dipped in soapy water. The soap keeps the compound off your skin and presses the bead into the joint.
7. Leave it to cure as the cartridge says. Do not paint a paintable bead, and do not let rain hit an exterior bead, until the tube says that it is safe. Use the cleanup solvent the cartridge names, water or solvent, and do not guess a solvent.

Stop when the bead is tooled, and the drainage path is still open. A wider void is not solved by a thicker bead. If the rod will not sit because the frame is loose or rotten, stop and treat that as a failed opening. Do not pack the void with scraps of the old bead, and do not switch to an interior tube because it is easier to tool.

What If a Gap Is Too Wide for a Bead?

A bead cannot bridge a void the backer rod does not fill, and extra compound only sags and cracks. A joint that wide means the frame and the wall have separated past a maintenance seal. Rot, a window that does not fit the opening, and a leak that continues after a sound bead are cases where a tube will not close.

What Window Caulking Will Not Fix

Window caulking will not repair rot, a window that does not fit the opening, a leak that continues after a sound bead, or fog between the panes. Fog between the panes is a warranty repair when Canadian Choice Windows & Doors™ installed the window, and rot or a poor fit is a replacement. A fresh bead on rotten wood sticks to a surface that is already breaking down. A bead stretched across a frame that sits proud of the opening, or sunk inside it, cannot square the unit.

"The call I get after a recaulk is that the bead looks fresh and the draft, or the leak, is still there. Another tube will not answer that. The next check is the window itself, the fit in the opening, the frame, and whether moisture is sitting between the panes," says Helen Sin, Consumer Success Manager, Canadian Choice Windows & Doors™.

Before you treat that as a failed window, lock the sash and feel the frame again, because a sash that is not fully closed will mimic a bad bead. Check the weatherstrip on the sash itself, since a torn strip lets air through the meeting point even when the perimeter bead is new. Check the corners of the frame for softness or a stain that has come back after the bead was replaced. If those checks are clean and the draft remains, the opening is the problem, and another cartridge will not change it. Note the opening that still moves air once the bead is new, because that frame is the one to inspect.

A soft, stained, or out-of-square frame is a replacement question, and the choice between full-frame versus pocket window installation depends on whether that frame can still hold a window. Full-frame work removes the old frame so you can address rot in the opening. A pocket, or insert, fit uses a sound frame and does not open the wall behind it. Caulk doesn't make that choice, and it doesn't hide rot.

A door perimeter uses the same exterior and interior logic as a window: a flexible exterior bead on the weather side, and a paintable bead on the inside trim. The door moves every time someone uses it, so the bead sees more movement than a window bead and shows pull-away when the joint is working harder. Leave the drainage path at an exterior door sill open in the same way. A door that does not fit the opening is not a caulk repair, and this bead is not covered by warranty.

A poorly installed window may cause cold drafts or let water into the house, and the damage that water causes is usually invisible until it is costly to fix. A new bead on the casing does not reset a unit that was never seated in the rough opening. That limit is about the installation, not a claim that sealant stops moisture on the glass. If the bead is continuous and the leak continues, stop buying tubes.

When the bead is sound and the draft or leak remains, an in-home appointment is how the opening gets measured and the frame gets checked. Ask them about rot, the fit, and fog between the panes. The visit is for one window that a bead cannot save. It is not a push to replace every window in the house.

How a New Window Is Sealed

A bead is maintenance on a window that already fits. It belongs on the top and the sides, in the right material for that side of the wall, and only after the old bead is gone. It does not repair rot, a poor fit, or fog between the panes, and it has to leave the weep paths open. On a new window, factory-trained installers at Canadian Choice Windows & Doors™, in the trade since 1997, seal the perimeter and leave those paths open, and before the window goes in, they replace faulty or deteriorating frame components in line with CSA guidelines.

When a sound bead still leaves a draft or a leak, window installation is the work that seats the unit, seals the perimeter, and leaves the weep paths open. That is the step for a window a tube cannot save.

Frequently Asked Questions

Are You Supposed to Caulk Around Windows?

Yes. Caulk the perimeter joint between the frame and the wall or trim, and only after removing the old bead. Seal the top and the sides, and leave the bottom exterior joint under the sill and the weep holes open. Do not caulk the glass of a sealed unit.

What Sealant Should You Use on Exterior Windows?

Use 100% silicone on a typical exterior joint, and use polyurethane where the joint is masonry, brick, or stucco. Acrylic latex is the wrong exterior bead in a Canadian winter. Check the cartridge for temperature, cleanup, and cure, and don't work below 5°C.

Should You Caulk the Inside of a Window?

Yes, as a finish and a minor air seal, not as the weather seal. Use paintable acrylic latex on trim that will be painted, and silicone-based acrylic in a humid room. Do not use pure silicone where the trim has to be painted.

Can You Caulk over Old Window Caulking?

No. The new bead will not bond to a cracked or loose old bead, and the old bead will pull the new one off. Cut out the failed material, clean the joint, and let it dry before applying anything new.

How Do You Caulk a Window Without Sealing the Weep Holes?

Seal the top and the sides, and stop above the drainage line. Keep the nozzle out of the small slots at the bottom of the exterior frame, and keep sealant out of the joint where the underside of the sill meets the wall. If dirt blocks a slot, clear it with a thin wire instead of covering it.

Why Does a Window Still Leak After It Was Caulked?

A new bead cannot fix rot, a frame that doesn't fit the opening, a sealed weep path, or fog between the panes. If the bead is continuous and water still enters, the window or the opening is the problem. Check that the bottom drainage path is actually open before you add more sealant.

How Often Should Windows Be Recaulked?

Recaulk when the bead is cracked, pulled away, missing, chalky, or hard, or when you feel a draft at the frame with the sash locked. There is no year count that replaces that inspection. A bead that is still soft and stuck to both sides, on a dry frame, can stay.