Fitting an oak windowsill

[Raymien]

Hi all, after some advice please.

A friend has asked me to replace some internal windowsills with oak ones. I’ve never fitted any before, but feel like it’ll be similar to fitting an alcove shelf, which is something I have done.

The prospect of movement and/or cupping concerns me, and I’m also not sure what I’d use to fit it with. Any tips from those who’ve taken on a job like this before?

Is it simply a case of using some 18mm or 25mm solid oak, putting a lip on the front and scribing it in, securing it with grab adhesive?

 

[treeturner123]

Hi all, after some advice please.

A friend has asked me to replace some internal windowsills with oak ones. I’ve never fitted any before, but feel like it’ll be similar to fitting an alcove shelf, which is something I have done.

The prospect of movement and/or cupping concerns me, and I’m also not sure what I’d use to fit it with. Any tips from those who’ve taken on a job like this before?

Is it simply a case of using some 18mm or 25mm solid oak, putting a lip on the front and scribing it in, securing it with grab adhesive?

Just so that your friend knows, oak windowsills will bleach quite quickly especially on the South and West elevations. If they have any ornaments on the sills, then these will create darker patches.

They look really nice when first done, but....!

 

[Etaf]

quite a few videos on youtube showing replacing windowssills - I have as a DIYer, only replaced 1 and it was going to be painted white - so i was able to get away with a lot more filling
do you have some photos of what you are replacing
do you know how the windows have been fitted ??? and are not on the sill at all
what type of windows and how old , and is everything in good condition
has the room been decorated and will you need to make good after

 

[niall Y]

In a sense you will be influenced by what is already there. If you can remove the existing window board then it will be a matter of slotting in an oak board to match. often the window sill has a groove to the inside that a bare-faced tongue slots into. This takes care of any shrinkage of the window board and any gap opening up It will be a neater job as well if the board slots beneath the plasterwork to the reveals.

As for fastening, then screws and plugs will be okay. If you need the fastening to be truly invisible and you can make use of the groove at the back of the board then a couple of pieces of strapping bent at right angles can be screwed to the underneath of the board and recessed in the plasterwork beneath the window.

A further thing to note is that, if you are messing around with plaster and fillers then the oak will need protected otherwise you could risk staining.

 

[Ollie78]

I have a method for this.
Cut the cill to fit and do all the roundovers etc.
Use a t slot router bit to make some tracks on the underside from the back edge to about 2/3rds (2 is normally enough but more if they are really long cills) then fix some pan head screws into the sub cill in alignment with the slots using whatever method is appropriate for the surface, one at the back one nearer the front.
Screw in the screws till they are just pulling it tight as you slide it in ( a test piece from mdf is helpful).
Fully finish the wood front and back then apply a couple of blobs of stixall or similar and slide it in place.

Really holds well and should prevent cupping but allow expansion accross the board width.

Ollie

 

[HOJ]

The prospect of movement and/or cupping concerns me

I make my window boards from an mdf base and a top skin laminate of Oak, about 8mm thick, with a separate piece machined as a nosing and applied.



(Off cut of some I made recently)

 

[Raymien]

Thanks for the replies. I've not visited the house to check the existing cills yet, however I believe from being there previously they will be a mix of wooden window board and tile. I don't know these are the ones they want replacing but these are windows caught in pictures I took of other work I did for them, and I presume they want the cills to match the oak.

The last couple of posts are particularly useful, thank you. Something for me to think about with the method of fit.