When deciding how to use caulk on your siding however it is generally more important to consider where you should not use it.
Caulking lap siding bottom edge.
It needs to move and breathe.
Wherever hardie siding meets a trim board the company recommends you leave a 1 8 gap between the siding and the trim and apply a 3 8 bead of approved caulking to protect and seal the edge of the siding.
The worst failure we have seen yet.
In my opinion caulking between the seams in any lapped siding either horizontal or vertical is not good practice but not just because of any potential vapor barrier effect.
It is generally not a good idea to use caulking on wood siding.
Pull the tip of the caulk tube slowly along the joint of the window trim and the siding holding the caulk gun at a.
If overused or incorrectly placed siding caulk can cause more damage to your exterior than good.
Also avoid caulking tongue and groove siding boards together.
Think of a wood home as a living thing.
Lp recommends applying primer the foundation of the house before painting the siding to prevent moisture from wicking into the siding.
Water is meant to exit through the bottom of each board.
Scrape the side of the window trim next to the siding and the immediate edge of the lap siding with a paint scraper.
After the paint dries apply caulk and then paint the rest of the siding.
How to caulk the window trim on lap siding 1.
Bottom of siding boards should not be caulked.
The bottom edge of lp lap siding is where the failure is first evident.
While paint does tend to somewhat glue these pieces together caulking them is never advised and can cause permanent damage.