Refinishing Window Sills, Restore & Repair: Complete Guide

You must be acquainted with windowsills since we are fortunate enough and have a home to live in. Windowsills are basically wood pieces that are horizontally attached to the window offering a feature of the ledge. Also, windows are meant to be closed on the sill board. In most old houses wooden window sills are found. However, for being exposed to direct sunlight for most of the time of the day, windowsills accumulate a lot of moisture. They are also a ready-made space for dust to settle.

These things are responsible for damaging window sills. That is why refinishing window sills are required on a regular basis to resist the damage. You cannot just protect the windowsills from being constantly exposed to the sun since windows are not meant to be closed only. So, you only have the option of regular refinishing of the sills.

Refinishing Window Sills

To talk about the sill construction, in most cases, sills are attached to the window frame itself. But in some cases, sills can stand horizontally in the bottom of the window as an alone piece. However, a damaged and dirty windowsill can make an unpleasant sight of the entire room.

So, you might be here to fix this problem. Well, then let us help you with everything about refinishing and restoring windowsills.

Refinishing Window Sills – A Complete Guide:

Refinishing window sills is a must job if you want a clean and fresh look of your room. This task is not tough and only requires some hours to be done with it completely. You will understand when you get to know the whole process step by step. But first.

Required Materials

  • Masking tape
  • Plastic sheeting
  • Drop cloths
  • Paint scraper
  • Putty knife
  • Wood filler
  • Sandpaper or Sander tool
  • Stain
  • Paintbrush

First, Prepping the Windowsills

For refinishing windowsills, you have to prepare the task and its environment first. You can do this prepping job by following some steps.

Step – 1: Protect the Areas Around Windowsills

For refinishing windowsills, you have to protect the areas around windowsills. Otherwise, the produced debris from a refinishing job might damage the walls and furniture near the window. So, it is necessary. Also, for easy cleaning when the task is finished covering the surrounded area is a wise idea. You can use masking tape to cover the areas including window trims and surrounded walls.

Tape the bottom of the windowsill. Also, cover at least 2-inches of both sides of the windowsill with tape. Where the wall and sill meet, cover the area as well with tape. Low-tack tape for painters is also a great material in this case. It does not pull off the paint with it from the wall.

Step – 2: Save the Floor

For covering the floor, you can use plastic sheeting. It helps in easy cleaning of the debris. Drop cloths are also useful for floor covering. Again, to make the working place less messy paper bags are helpful as well.

Step – 3: Open the Window

When you are done covering and taping the walls and trims, open the doors of the window. Wide-open the window so that the entire windowsill is revealed. Doing the finishing job keeping the window closed will be very uncomfortable.

Then, Sanding and Removing Paint from Window Sill

In many cases, windowsills come with stained wood. However, in some cases, they are painted as well. So, before you get to start sanding the sill, you need to remove the paint from the wood first. Otherwise, you cannot go for a new finish.

Step – 1: Use Paint Removal

paint scraper to remove paint from window sill

Using a paint scraper is useful for removing previous paint from the windowsill. You can use it along with a putty knife. Both tools work effectively on paint removal. However, while removing paint be careful with the caulking. If you pull off any portion of caulking or find any voids then fill the gaps again and make it smooth with the help of the putty knife. Let the caulking first for about a day before going for the next step.

Step – 2: Sand the Window Sill

Now, it is time to sand the windowsill. Using a sanding block for this purpose would be a good idea. But first, start with the one that has a coarse grade. The coarse sand blocks will help deal with larger high points. Also, to remove old varnish using this grade sanding block is appropriate.

Again, for previously painted windowsills, sanding with coarse rough grit sandpaper is helpful. Go with 80 to 100-grit sandpaper. Since there might still be some paint left after scraping the paint, sanding with this sandpaper will remove the rest. Moreover, if you are up to refinishing the wood stain of the windowsill then this might also help in removing the wood sill top layer.

You can sand the windowsill down until it reveals its natural wood surface color. While sanding first start from coarse-grit to medium and then to fine-grit sandpaper according to the finishing requirements. So, when you remove the stain from windowsills sanding with coarse and medium-grit sandpaper, smooth it again with a fine-grit one. Use 150 or more-grit sandpaper to prepare and smooth down the surface of the windowsill for further process. Following this way, staining or painting windowsills becomes easier.

Sand Window Sill with sheet sander

However, many people look for a quicker way to sand the windowsill. If this is the case, then you can use a sander tool for sanding the windowsill. A Palm Sander or detail sander is best fitted for this purpose. It comes with a sanding plate of iron shape. This shape is suitable for reaching out corners and tight edges. Must Read: 8 Best Sander for Window Sill Sanding.

This power sander is also useful in dealing with deeper scratches. Using a medium grit of 100 or 120, you can sand the deep grooves until they get smooth. Moreover, there are palm sanders of different recognized manufacturer brands available that are good for sanding windowsills. Read Also: How To Sand Trim & Baseboards to Get Smooth Finish

Step – 3: Meanwhile, Fill the Holes

If you did not fill the nail holes before, fill them while sanding. You can use wood filler for filling purposes. Grab some filler with the help of a putty knife and fill them into the holes. Wipe off the excess filler and then let the holes cure first. Then sand the filled holes again slightly to make the surface smooth.

Step – 4: Deal with Tight Edges

Many people forget to sand the tight edges while doing this task. But it is also a crucial part. If you leave the places without sanding later, they will create a yellow hue after finishing. It will ruin the whole purpose of the task. To deal with the tight edges of the window sill you can use bits of sandpaper paper and apply with the help of a screwdriver. Since the sanding job comes with a lot of dust make sure you wear protective gear while doing this.

Step – 5: Wipe Down the Windowsill

When you are done with sanding and removing the painting, wipe down the windowsill. Sanding wood windowsill produces a lot of dust and small particles. Make sure you wipe away all debris and make the sill surface clean. Be aware of the fact that the sealer won’t make a better performance if any debris is left on the surface. So, prevent them from lodging in the sealer.

Lastly, Refinishing the Windowsill:

After prepping and sanding the windowsill lastly, it is time for refinishing. Though this part comes in the last yet you have to be more careful in it.

Step – 1: Be Ready with the Stain

Before applying the stain directly on the windowsill, shake it well or stir properly. It helps to incorporate all the elements of the stain with each other properly and evenly. Put on your protective gloves as well for protecting yourself from being stained.

Step – 2: Apply the Stain

Now, take a paintbrush and dip it into the stain. Then apply to the wood windowsill. Go in the same direction making the wood grain stained. For detail work and reaching out the corners properly, you can use a small paintbrush. Use it to stain the crannies and nooks of the windowsill. Even though using a paintbrush is the best tool for this task yet you can use a sponge or old rag as well.

Just make sure you are applying the stain evenly over the sill surface. After applying the stain, wipe away the excess stain using an old rag. Wipe across the surface to have an evenly stained surface.

Step – 3: Let the Stain Dry and Apply Sealer Coats

After applying the stain properly let the windowsill surface dry thoroughly. The curing time is instructed in the stain can. So, simply follow the instruction and do accordingly. Make one or two coats of sealer. Let the sealer dry between each coating. When you are done and the windowsill surface is dry remove the tape and plastic sheeting. Clean away the rest of the debris and there you get a refinished windowsill.

What is the Best Finish for Wooden Window Sills?

Well, there is a wider range of paint finishes available for wooden window sills. Depending on your need you can choose any of them.

a) Eggshell Finish:

Till now eggshell finishes are the best for interior wooden windows and door frames. It is basically a particular sheen of gloss. It comes with practical and long-lasting elements. It brings an attractive appearance without showing much glossiness. For concealing flaws especially damaged windowsills eggshell finishes are great.

b) Satin Finish:

After eggshell, satin finishes are the second-best finish for wooden window sills. If your windowsills lose their shine frequently then satin finishes are undoubtedly a great option. They are also low maintenance. In fact, satin finishes are highly used for finishing and refinishing windowsills.

c) Semi-gloss Finish:

It is also a frequently used finish on areas that are mostly exposed to sunlight and moisture. This finish has a medium sheen that offers a perfect look.

d) Gloss finish:

Gloss finish is considered the best for highlighting wood pieces or any art pieces. For doors and windows, gloss finishes are good to go. However, the only downside of a gloss finish is that it comes with expensive rates.


Question: How do you Restore a Wooden Window Sill?

Answer: Your wooden windowsill might run out of moisture because of constant exposing to dry conditions and sunlight. Therefore, restoring the wooden window sill becomes a need. However, you can simply restore it by using a perfect solution of paint thinner and linseed oil. Just mix the two components and apply them all over the wood surface of the sill. Then let the coat dry for about a day straight. After 24 hours you will see the wooden window sill has restored its previous appearance.

How do you Repair a Stained Window Sill?

Window sills can be stained in many elements. It can be water-damaged or stained in many ways. In these cases, to repair a stained window sill first, sand the stained areas properly and make the surface smooth. Then stabilize the wood that is about to rot. You can use several wood hardeners that are available in the market. Or also, you can bleach away the stains from the sill surface as well with the help of oxalic acid.

However, after stabilizing and bleaching away, sand and discolor the windowsill surface. Then re-stain the sill again and finally, apply a clear coat.

How to Sand Window Sills Before Painting?

Sanding window sills before painting is a bit tricky. First, you have to go with coarse-grade and gradually end up sanding with fine-grit sandpaper. However, for woody windowsills, you can use aluminum oxide fine paper. Just sand over the surface slightly and in a circular motion till it removes all flaws and old paint.

If there are patches on the sill surface already then sand the patches as well till they flush with the rest of the areas.

What Sandpaper to Use on Window Sills?

To start with coarse sandpaper of 80-grit will be the right idea. Later use 150 or 170-grit sandpaper to have an even and smooth sill surface.

How do I Protect my Window Sills from the Sun?

To protect your window sills from the sun, you have to take good care of them. You can occasionally refinish your sill or to prevent it from being damaged be extra careful. When you notice the window sills are starting to look dry, coat restoring teak or linseed oil product. For regular maintenance, you can use some commercial restoring products that are meant for window sills.

Last Updated on July 16, 2022 by Rogers Weber

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