Harry wrote:
Hello,

HomeDepots' Pacific Knotty Cedar; 6 pieces to the package;
5/16" thick x 3.5" wide x 8' long; installed coverage 14 Sq ft.

Iam installing this on a CapeCod ceiling/(actually roof) (and,
yes, i know better, but that is a long story).

The ceiling doesnot come to a peak, but is flat for
3 and1/2' down the center (side walls are 39").

This is going to be the ceiling to this bedroom. Iam installing
it in the manner of a porch roof, on to 2 by 6, ceiling rafters to
rafter (there is bats of fiber-glass insulation behind these fragile
planks). There is a 2 foot space between each roof rafter. What
is the best way to do this?

Thank you for any help at all.

To replicate shiplap (which is what it was called here a 100 years ago)
I was given some very good advice on this same product. As tedious as
it was I ran a v groove down the center of each board the same depth as
the slight edge bevel where the T+G meet. This not only gave it a
shiplap look but eliminated the risk of cupping which is common in this
product. Where there was no peak I just filled the join area with some
1/4 round. I, like you just put it straight to the rafters without any
strapping. The entire 2 story house has this on the ceilings and now in
year 7 with no concerns. If you use a lower grade of the product be
prepared to have 20-30% of the product unusable. I used a nail gun and
nailed straight in as opposed to nailing into the tounge - splits too
easy.

GL