It needs to move and breathe.
Caulking cedar lap siding.
Corner boards are applied to the sheathing with siding fitting tightly against the narrow edge of the boards allowing for expansion and an adequate caulking bead.
When deciding how to use caulk on your siding however it is generally more important to consider where you should not use it.
It is generally not a good idea to use caulking on wood siding.
The answer depends on the manufacturer and installation method used when the siding was first installed.
Think of a wood home as a living thing.
Natural siding boards are designed to expand and contract with the elements and we do not want any adhesive to prevent their natural movement.
I m not a painter but i do install cedar siding and i always caulk all the joints.
How to caulk the window trim on lap siding.
Whether you are repainting replacing a window or replacing the siding on your house the caulking around the window trim is a very important element.
Width is a matter of taste and proper proportion.
If i install a non finished product i usually go with a 3m paintable caulk.
If i am installing a prefinished product which i do mostly i use a color osi match caulk.
If overused or incorrectly placed siding caulk can cause more damage to your exterior than good.
Caulk by its adhesive nature will try to limit this movement leading to widespread failure and cracking in the caulk over time.
Generally we do not recommend caulking butt joints on cedar siding.