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How To Paint Sash Windows


Start with removing all ironmongery (locks and handles etc.) from the window frame. Preparation is key to a good finish, so spend a bit of time getting this right. Sash windows fit tightly together and with more paint they tend to get tighter. So at some point in the life of a sash window it may be necessary to strip everything back to wood, but if the existing paintwork is in reasonable condition then just a good overall sanding may be required.

To easily get to all the parts of the window, reverse the sashes. Lift the bottom sash up as high as it will go and pull the top sash down. It’s not necessary to put masking tape on the glass. Don't worry about paint on the glass, it’s easy to remove with a razor blade later.

Sanding & Priming

Sand the woodwork carefully, removing any old flaking paint, bubbles, old paint drips etc. Course abrasive followed by a finer paper such as 180-grit should be used and close attention paid to all the little crevices etc. Now use an old paintbrush or a tack rag to remove any dust from the sanding process. Now wipe over with white spirit to remove any lingering dust and grease. Apply a coat of exterior primer, and allow to dry (this normally takes about eight hours).


Start with painting (using good quality outdoor gloss paint) the bottom section of the sash (the one which you have pushed up to the top). The mullions should be painted first. These are the slim division strips within the frame that retain the panes of glass. Then paint the mullions in the other sash. You will not be able to get to them all but paint the ones you can. Now paint the face of the frame on the lower sash which you have pushed to the top, and then the rebate under-side, into which the top sash will be positioned when the job is complete. Push the top sash back up, just stopping short of any painted surfaces meeting.

Paint all remaining mullions and frame faces. Anything you could not reach before should be now accessible to paint. Finally paint the frame casing and the widow sill. When paint is dry you can start to tidy-up any of the paint on the glass panes. Push the scraper blade or razor blade onto the glass and scrape in the direction of the mullions. Then hold the blade vertically and scrape along the edge of each mullion where it meets the glass. Be careful to ensure that the paint on the woodwork still overlaps the glass a small amount creating a watertight seal, otherwise the exposed wood will be subject to rot.


To see The Paint Shed range of paint and materials for sash windows and other woodwork projects, please check with our website. And remember, any help or advice you require, just contact our experts directly.

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