How to replace timber windowsill without removing window?

Stuart24

Hi, I am wanting to replace the window sill to put in a new sill that extends past the wall and returns past both sides of the window.

I’ve looked underneath and confirmed that the window is sitting on top of the timber. Is it possible to remove and replace just the sill without replacing the sides and leaving the window in place? House is brick veneer.

Thanks

JacobZ

Welcome to the Bunnings Workshop community, @Stuart24. It is wonderful to have you with us.

If the aluminium window was installed on top of the timber frame, then it is unlikely you can completely remove the sill without causing water ingress issues or needing to remove the window first, however I don't think what you are proposing is impossible, you'd just have to take a slightly different approach.

My suggestion would be to cut the sill flush with the aluminium frame and the sides using a multitool to plunge cut through the timber. You can then lever the cut section of the sill out using your prybar, making additional relief cuts if necessary, or by finding the fixings using a https://www.bunnings.com.au/trojan-magnetic-stud-finder_p0673723 and simply lifting it out. This will leave a portion of the existing sill beneath the stiles and the window frame, so there will be no drop in height or gaps that should open up.

You would then simply cut your new sill to size and shape, slot it into the opening, attach it to the brick using masonry plugs and screws, cover the screw heads, caulk the seams, sand, prime and paint.

Allow me to tag some knowledgeable members to see how they'd tackle it and if they have any thoughts to add - @Nailbag, @Dave-1, @JDE.

Let me know what you think and if you have further questions, please don't hesitate to ask.

Jacob