iDoStuff index

DIY stuff

Timber buy & prep
Draught Proofing
Timber front door
Wooden Motorcycle
Fitting Cast Iron Railings
Sash Windows
Zimmer steps
Opening a fireplace
Brickwall rebuilding & pointing
Hand Hewing Timber beam
Joist end repairs
How to Install Flue Liner

PRO stuff

Cherry Picker Information
Rotational Moulding
Creative Photoshop Artwork

Property stuff

Whitby Cottage Renovation


Digital Marketing stuff

Personal Development stuff

Random stuff

Is a Wood Burner Worth it ?

Wood burning Stove



iDoStuff blog
Whitby Cottage Posts
Stuff from the other half (wife)
DIY Loft conversion
DIY Sliding Sash Windows


Using filler to repair windows

If you've arrived here direct from a search, you might want to read the full set of pages starting here

Epoxy wood filler on window repair

Don't expect filler to work as mass filler. If you have big holes gaps read the previous sections.  Filling follows on from splicing in new timber.

If the pieces have been cut well there won’t be much filling required. Due to the nature of wood expanding and contacting with changes in moisture content large volumes of filler should be avoided. 

The wood filler doesn’t expand the same with moisture so the difference will / can cause cracks to appear. So it best to keep filling to minimum. You might be tempted to fill areas with filler on its own but it is always best to bulk out any repairs with timber.  The holes of the screw heads, small gaps around the spliced in edges and thin surface filling will be fine. But please read the note below.

Scarfed in piece filled ready for painingNote: Wood moves, filler doesn’t. As discussed this effects the amount of filler that should be used.  There is also another major consideration.  The moisture content of the frame and spliced in pieces will be different.  The frame being rotten indicates that the water content is high and will be swollen, where as an old piece of timber, stored dry used for splices will be not shrink back but may expand. 

Over time the frame and new piece will stabilise.  The old frame sections are likely to dry out and shrink as the repairs have stopped moisture getting in to the wood. The flexibility of the filler may not be enough to compensate so gaps and cracks can be expected.  Final finishing /painting should be left for weeks (weather dependant) so any remedial filling can be done.  Also have a look at the Finishing / Painting section – modern paints will trap moisture in the frame.

Wood Filler for windows

I use epoxy wood filler. Mixed in small batches and pressed well in. This can be sanded or pared back with a chisel after half an hour and any low spots filled again. It's not worth doing a big fill all at once as you'll end up with load of paring back and sanding to do.

How much care and attention you put in to this is your choice, I don’t usually aim for a perfect invisible repair. Although it can be done, as the note above explains, major time spent on perfection at this stage may be undone as the timber stabilises.  


Next: Glazing and putty


Previous: Other Window problems and considerations including sash window double glazing

Please post any questions, comments or suggestions over on the blog


Window repairs intro and index

Investigating the extent of damage

Paint stripping windows

Making good a timber frame or sash

Other Window problems and considerations including sash window double glazing

Replacing window parts

Fixing loose joints

Swollen sticking sashes

Fixing hinges

Filling and sanding window repairs

Glazing and putty

Priming and painting