Wooden external Window sills - Issue with the gaps

[Nigel123]

Hi All,

I was wandering what the best solution is to sort out the very small gaps on wooden external window sills (bay window). Every couple of years I seem to have to revarnish them because cracks appear on the joints of my bay window.
In the past I have used wood filler and obviously movement has caused this to crack.- it seems I Need a more flexible solution?
Should we be using Chaulk or some silicon filler?
Recommendations for a smooth finish that can Varnished (again) in an oak colour would be great fully received.

 

[Johnny Allround]

Can you send a photo of your window please?

 

[Nigel123]

I am sat in my office in London , thinking about DIY jobs I need to do. - I will post a photo tomorrow - thanks for responding

 

[Johnny Allround]

Good afternoon Nigel, the reason I asked to send a photo of the job is there a lot of very knowledgable diy and tradesmen on this site and will very quickly give you a solution to your problem. Hope this helps.

 

[Nigel123]

Thanks Johnny - It would be great to hear of a more permanent solution than just varnishing every few years - Definitely will post photos tomorrow.

 

[Notch7]

Every couple of years I seem to have to revarnish them because cracks appear on the joints of my bay window.
In the past I have used wood filler and obviously movement has caused this to crack.- it seems I Need a more flexible solution?

You will always get cracks on the joints of a segmented external cill.

It is because timber expands and contracts mostly tangentially, so when wet the cills will get wider causing the joints to open up.

The permanent solution is to carefully chisel a small 45 deg V at the joint (IE effectively a chamfer off the end of each mating half). very lightly sand so you dont have a sharp edge at the start of the V. the V is about 4mm or so across the top

strictly speaking the correct way is it sand or machine a 3mm radius on the ends of the cills before assembly. A radius is perfect because the film thickness of the coating remains the same around the radius. Sharp corners always means film thickness goes down to almost nothing.

The pros would then use a V joint sealer, but it may not be worth that for a few joints -but it is the way the professional joinery companies do it (I used to run a joinery company).

example here
https://www.glenwooddecoratingsuppl...teknoseal-4009-v-joint-sealer-tube-320ml-p797

clear MS silicon will do the same thing but you would need to test it to see if the varnish adheres ok.

 

[Nigel123]

Thanks Notch7 - perfectly explained - with a solution

 

[Nigel123]

 

[Nigel123]

Hi Johnny - hopefully the photos show the problem.
I have 2x Bay Windows with 4 joints each and also 2x smaller ones with 2 Joints each.

regards
Nigel

 

[Johnny Allround]

Old age is the problem Nigel.that cill has passed its sell by date. However a good sanding down to reveal the extent of the damage would be a good start.once you have got to that stage then you can start the repairs. It will only ever be a temporary fix it will always need some tlc.

 

[Nigel123]

Thanks Johnny - I would prefer to do complete window replacements but the Wife doesn’t want the internal mess/hassle it will cause.
So down to me with a bit of hard work

thanks again both of you