On Nov 8, 11:34*pm, George wrote:
On Tue, 8 Nov 2011 07:55:33 -0800 (PST), RicodJour
wrote:









On Nov 8, 8:08*am, George wrote:

I am looking at LP 'Smartside' lap siding. *The installation
instructions say to leave a 3/16" gap at butt joints. *I assume this is
for expansion? *You're supposed to caulk it, but it seems huge. *Is this
different than regular wood clapboards? *I thought they were supposed to
be snug at the joints.

Sawn wood products exhibit movement radially and tangentially to the
grain - there is not a lot of movement along the grain. *A sawn wood
clapboard will expand and contract a small amount in height and
thickness due to changes in humidity, and to a much, much lesser
extent temperature. *The length will not change.

LP's Franken-wood is made up of wood fiber and a lot of binder -
plastic resins, and due to this there will be more movement in length,
and that is why there is a need for an expansion gap.

I don't doubt what you say, but I have trouble picturing it. *The boards
will be nailed through the sheathing, into the studs. *If the siding
lengths change, ... what? *ISTM, either the whole wall moves along with
them, or the nails pull up. *Or something.

Siding nails are very thin and they can and do bend a bit. It's a
system - everything in it moves. Nails, siding, sheathing, framing -
everything.

R