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How to restore weathered wood window sills?

A few wood window sills in my house are very weathered and in a bad state. There are small cracks (may be window checks?) . How do I restore these window sills?

Do I start with cleaning with water then sand with 120 grit sandpaper? Do I need to fill those little cracks before applying exterior varnish? Thanks

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MitchellMc

Hi @mmchau,

I'd skip the cleaning part since you'll be sanding them back. If you have several windows to do, I recommend picking up a detail sander. Start with 120-grit sandpaper to remove the deteriorated timber on the surface, then drop it down to 180 to remove scratch marks, and then 240 for a smooth finish. Once you've achieved a smooth finish and all the deteriorated timber is removed, those cracks will be substantially less noticeable. If it looks fine, you can coat the timber with varnish. If you are still concerned about whether you need to fill the cracks, post a picture after sanding, and we can advise.

Please let me know if you have any questions.

Mitchell

mmchau

https://www.workshop.bunnings.com.au/discussion/comment/34787#Comment_34787

Thanks for your prompt reply @MitchellMc I have a random orbital sander at home. Can I use this instead of detail sander? Sorry I don’t really know the difference between the two.

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/79703#Comment_79703

You can @mmchau, but a detail sander is better at getting into the corners. You could use the random orbital and then hand-sand the corners.

Mitchell

mmchau

https://www.workshop.bunnings.com.au/discussion/comment/104268#Comment_104268

Hi @MitchellMc

I have sanded one window sill using 120 grit then 240 grit (out of 180 grit sandpaper at home while working on it). The cracks on one end are still present but improved. Do you think I need to fill these cracks?

Which varnish do you recommend? It looks like the window sill has been painted previously so do I need to sand off all the old paint first prior to applying varnish? Thanks

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/119227#Comment_119227

Hi @mmchau,

You don't need to fill these cracks, but it would improve the look of the sill if the filler was colour-matched correctly. If you don't mind the current look, then I'd be inclined to just varnish it.

It looks like you've sanded through the majority of the paint, but if there is some left, it would be best to remove it. It looks like you've sanded pretty well on the front, but the area closest to the window is still a bit rough. You could drop back down to 80-grit is the 120-grit was struggling to cut through the deteriorated timber/paint.

This Cabot's 250ml Satin Water Based Cabothane Clear Interior Varnish would be suitable for your sill.

Please let me know if you have any questions.

Mitchell

mmchau

https://www.workshop.bunnings.com.au/discussion/comment/128191#Comment_128191

Thanks @MitchellMc !

My preference is to fill those small cracks. Any wood filler will do the job I guess? This window gets lots of sunlight and hence very weathered

EricL

https://www.workshop.bunnings.com.au/discussion/comment/133995#Comment_133995

Hello @mmchau

My best advice is to make sure that the filler that you use is rated for outside use. An example would be the Earl's 0.140kg White MulTfill Ready To Use Filler. It's available in several colours and works with timber.

If you need further assistance, please let us know.

Eric

mmchau

https://www.workshop.bunnings.com.au/discussion/comment/137629#Comment_137629

Thanks @EricL ! Can I please ask why using the exterior grade filler?

EricL

https://www.workshop.bunnings.com.au/discussion/comment/140123#Comment_140123

Hi @mmchau

It has UV additives and made to withstand harsh weather conditions. Looking at the windowsills it appears to be in direct sunlight. Any extra protection you can provide will make it last longer. You'll note that the sample I suggested can also be used for indoors. So, you are covered whether applied inside or outside.

Eric

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