"Ken" wrote in message
oups.com...

Ranieri wrote:
"FACE" wrote in message
...

I have noticed that a lot of my lap siding boards have a small (1/16
to 1/8) crevice where the boards lap over one another -- that is where
the thin top edge of the beveled siding (3/16?)goes under the the
thick (3/4?) bottom edge of the next upper board.

I am painting the boards. Should I caulk all of these crevices?



Definitely not.

I'll second that. Any moisture that gets behind the clapboards needs a
way to get out. Caulking will hold in moisture and rot the clapboards
from the inside out. A general rule-of-thumb (but not always true) is
to caulk vertical cracks, but not horizontal ones. Many times a
horizontal seam is where water is meant to leave a structure.



Yes - in addition, lap siding is meant to expand and contract across the
width of the board - sometimes a pretty significant amount on wider lap
siding.