How to seal the sides of window sills and gaps in wooden facades?

[kia2]

How do you seal a large hole on the sides of a window sill? I assume I need to fill the hole with something other than sealant first? What? And then I seal it, but with which sealant?

I also wonder what type of sealant is suitable for gaps in a wooden facade.

Attaching photos.

And THANK YOU for the help in advance!

 

[prototypen]

Has the window been replaced?
I think it looks like it's time to replace the boards.

Protte

 

[kia2]

Has the window been replaced?
I think it looks like it's time to replace the boards.

Protte

You mean on the whole house?

 

[AndreasLarsson89]

You can use backup rod and regular acrylic sealant for outdoor use. If there are too many places on the house, you might want to consider replacing the siding instead.

 

[Huddingebo]

Stretch out the edges of the sheets so they press against the wood and paint a little.
Works excellently.