Repair finger join

[Rockydinosaur]

Hi,
I hope someone may be able to help me. I have a finger join in a window sill that I need to paint. I have attached a couple of photos to show the join.
I need to paint the window surround but need to repair this first. Is there a glue / adhesive that will fill this joint and not split again after painting.
Any help would be much appreciated.

[artme]

Polyurethane glue will do the job.

Push it into the joint - Make sure to use a glove - let it cure and the it can be sanded back.

If you haven;t used PU before now, be aware that it expands and sets so it looks a bit like PU
foam.

[elanjacobs]

The only reason PU expands is because of the gas bubbles created from the reaction with moisture in the timber (which is how it works) being trapped as it sets. It's not designed to fill gaps.
I'd be going with epoxy resin instead

[steamjunkprops]

Bit of 15min epoxy should fill that, try adding a bit of talc to thicken it up a bit.

[artme]

The only reason PU expands is because of the gas bubbles created from the reaction with moisture in the timber (which is how it works) being trapped as it sets. It's not designed to fill gaps.
I'd be going with epoxy resin instead

This is true, however I have used PU Successfully in this manner. If needed the area can be wiped with a damp rag before applying the glue.

My first thought had been Builders' Bog but I'm not sure how well it would hold up with later wood movement.

[Master Splinter]

I think that Builder's bog and similar polyester resin based fillers really don't have a role in anything to do with wood (or metal for that matter) as the adhesion isn't that good. Better off paying a bit more and using epoxy, as the price difference isn't that great. To increase the chances of the fix holding over time I'd use a syringe to see how much I could force in there.