How To Repair A Broken Window Sill

Window sills are quite decumbent to impairment from pets, plants, and weather over fourth dimension. Repairing or replacing quondam window sills is an easy home repair project that just takes a few hours and basic tools.

Before and after photo of window sill replacement.

We dearest our homes, but they aren't impervious. Unsightly cracks, dings, and everyday damage tin can build upwards over time and window sills are quite prone to damage from pets, plants, and weather. A interior window sill is the bottom portion of the window, and commonly has a lip that overhangs the trim molding.

In today'south tutorial, I am showing how to replace interior window sills from some of the most common issues:

Rot
H2o Damage
Bubbling MDF or pressboard
Pet damage and deep claw marks

Repairing trim is actually practical, economic, easy to install, and only takes, at most, a few hours!

Top down view of a pet damaged wood window sill before repair.

So, first, we take the crime. There'southward actually 3 of these that look this bad. This damage is all from a wonderful pup we rescued. Unfortunately, he had astringent separation anxiety, but it seems to have calmed down afterwards a twelvemonth of working with him. So it'south time to say goodbye to this eyesore!

Tools and Materials

Hammer or prybar
Utility Knife
Hand Saw or Jig Saw
Nails or Brad Nailer (This is the top rated kit we employ)
A board and router or a millwork lath to match the other sills in your home
A product to stop rot (y'all may or may not need this merely we have used this one in the by)
Wood Filler
Putty pocketknife
Level
Trim Caulk

Removing Window Casing and Sill

The first step is e'er the nearly worrisome, right? The window itself isn't actually fastened to the interior sill. The sill should be installed into the framing.

Step 1: Remove any side casing

Casing is trim that is around the outsides of doors and windows. Not all windows have casing, every bit our was just connected to drywall and caulked to hibernate seams. You will likely have to remove this because the casing sits on top of the sill, preventing the sill from moving upward.

The photos below are of me removing door casing, just all the same steps apply.

Step by step instructions for removing casing.

To remove casing, cutting the caulk line on both sides that hides the drywall and window framing seal. Drag a razor knife top to lesser to do this, making certain to get the full caulk line if you tin. Cut any caulk around the sill equally well. (photo 1)

I utilise a crowbar to pull out the casing from the drywall. If prying, make certain use a brace against the wall so you don't dent the drywall. (photo two) Cleanup the excess caulk and remove nails/staples. (photo three & iv)

Often times the casing tin can be salvaged and put dorsum on if you are careful, simply sometimes it needs replaced.

Step 2: Pry off the sill.

Use a prybar or chisel to slowly pry the sill upwards. A hammer also helps. Continue the sill in 1 slice so you can use it equally a model when cutting the new sill. So set it aside for later.

Window frame with sill removed from the wall.

Dealing with Rot

At this stage, the biggest matter to watch for is any rot that may be effectually the frame. Rot will need to be removed, or it will continue to spread. If you exercise find pocket-sized mold or rotted forest, replace or make clean and use a product like this to stop rotting.

Rot needs ii things to happen: a illness inducing leaner or mucus and water. Make sure that you are fixing the source of the h2o that caused the rot.

If y'all detect major rot (structural or the water source tin't be constitute), here is where I recommend seeking professional assistance as the window and framing may demand to exist replaced.

Later solving those issues, if whatsoever, hither is a great opportunity to make full any gaps if they exist to ensure a more air tight seal. Take window spray foam and spray into the gaps and let to dry. Cut abroad the excess foam with a razor blade prior to installing the new sill.

Pace iii: Cutting The New Sill

Closeup of the bullnose end of a window sill overlapping the wall.

We made our own here. A elementary run across the router to create a bullnose edge makes any appropriate board a proper sill. If you do not have a router, almost window sill material can exist found in the millwork section at a habitation improvement store like Domicile Depot. Here is an example like to ours. You lot will need to cutting it to size however. Mark the board using your template from previous sill and cutting.

Step 4: Attach new sill

Use nails or brad nails to install the forest board into identify ensuring to nail into the framing beneath. I do not recommend gluing equally it isn't needed and will make any future repairs more difficult.

New window sill with nail holes around the edges.

Footstep five: Add Window Trim

If yous had casing to remove effectually the window here is when you can reattached around the window.

Footstep vi: Final Touches

This is both the easiest and longest pace for professional results. Depending on your particular situation, you may need to:

Make full and smooth all nail holes with wood filler in wood areas.
patch whatever dings in the drywall.
Caulk effectually the edges of all the window trim and frame.
Prime and paint equally needed to lucifer the existing trim in the house.

In our case, the window trim under the sill had some gouges and dog chewing damage besides. I elected to fill this detail piece as the edge cuts are non easy.

Damaged door casing under a window with wood filler in the chew marks.

Expert Tips

I accept used a lot of wood filler and this is my favorite product. I thinned it out with a bit of water to become in the smaller areas.
For filling this type of wood, I love these sponges because they have edges that I tin can easily control and get into the ridges.
Try to observe real wood products rather than the paper-thin-like pressboard that new houses use. It is a much better product that is easier to work with and is less prone to harm and problems.
If you would like more information on caulking, bank check out our step-by-step guide to Caulking baseboards.

Finished photo of new window sills and white trim. Dark Gray Curtains blue dining room

LOOKING FOR MORE Unproblematic WAYS TO IMPROVE YOUR Dwelling house?

The Easiest Mode to Make Baseboards look Beautiful Over again
Brand Basic Cabinets Look Expensive with Trim
Building A Custom Cupboard
How to Paint Quondam Kitchen Cabinets

Well, now that'due south over, the dining room makeover will look much more finished. It'southward hard to make a room inviting, cozy, and beautiful with heart sores such as these. If you want to see our finished dining room makeover, check out our home bout tab with all of our before and later on makeovers.

Frequently Asked Questions

How exercise you gear up peeling paint on a window sill?

Scrape off any peeling pigment. Use a paint stripper or sand with 120 grit sandpaper until polish. Vacuum and wipe all dust off, and so paint with 2 coats of durable pigment.

Why do window sills rot?

Rot needs two things to happen: a disease inducing leaner or mucus and water. Although sloped, a windowsill is a horizontal shelf where water can accumulate. The beginning footstep to repairing rot is to remove any exposure to the source of water.

What finish is best for window sills?

A highly durable paint or poly topcoat is essential for protecting a windowsill. Cheap paint often becomes mucilaginous and items attack it can stick. Use a satin or semi-gloss paint that is UV resistant.

How much does it price to supervene upon a window sill?

Whether interior or exterior, materials cost less than $50 for forest window sills. If you have to hire a contractor, expect to pay additional labor charges of $100-250. Both calculations presume there isn't more extensive impairment to the window or framing, which would increment costs.

Weekend DIY project. A pegboard organizer in the craft room above the desk workspace.

More Trim Tutorials

Kitchen Island with Trim on it but not painted. — Adding Trim to an Island

Crisp baseboards and molding make a wall paint shine. Repairing and caulking baseboards doesn't have to be scary with these pro tips. — Adding Trim to an Island

PS I honey seeing your creations! Be sure to take a photo and tag#cravingcreative on Instagram! Yous can alsostay in touch with me through following me on Instagram, Pinterest, and Subscribing to the Newsletter!

Two windows with blinds closed and grey curtains on either side.

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Hand Saw or Jig Saw

▢ 1 Window Sill Board cut to length
▢ Wood Filler
▢ Nails ii inch finishing nails or brad nails
▢ Trim Caulk
▢ Pigment
▢ Drywall spackle

Cut the caulk line around both sides of the casing and the window sill itself. Drag a razor knife top to bottom to exercise this, making sure to get the full caulk line if you tin.
Use a crowbar to pull out the casing from the drywall. If prying, make sure to employ a caryatid against the wall so yous don't paring the drywall.
Use a prybar or chisel to slowly pry the sill up. A hammer also helps. Try to go along the sill in one piece so yous tin use it equally a model when cutting the new sill.
Measure the sill area and use the erstwhile sill as a template if possible. Cut the new sill to size. Dry fit several times equally the walls is likely not be completely straight.
Apply nails or brad nails to install the wood board into place ensuring that it is nailed into the framing below.
Reattach or replace the side casing and trim that was removed with nails or brad nails.
Complete the finishing of the window. Make full and polish all smash holes with forest filler and patch walls if necessary. Caulk effectually the edges of all the window trim and frame. Prime number and paint equally needed to friction match the existing trim in the business firm.

General Tips

I have used a lot of forest filler and this is my favorite product. I thinned it out with a fleck of water to make it the smaller areas.

For filling this type of wood, I dear these sponges because they have edges that I can easily command and go into the ridges.

Try to find real forest products rather than the paper-thin-like pressboard that new houses utilize. It is a much improve product that is less prone to damage and bug.

If you lot would similar more information on caulking, cheque out our pace-by-stride guide to Caulking baseboards.