Hi Al,

would it be feasible to afix a longish, shallow "L" bracket to the
ceiling to support one end of a board while I worked with the other
end and over towards the bracket, moving the bracket over every
couple of boards or so?

It's certainly feasible. I'd probably whip something up that I could slip
over the edge of the installed boards that I could in turn set the new
board on temporarily. Then just slide it off and move it where you need
it next.

However, as another poster mentioned, it probably won't help much with
T&G boards, and you probably won't need it anyway.

I installed 1x6 T&G cedar ceilings throughout our house and had no
problem installing 8-10 foot boards solo, once the first row was
installed (for that you might need the "helper" board on one end to get
started).

Essentially, you can slip the groove on one end of the new board, over
the tongue of the already installed board, and work your way down. With a
5-1/2 to 6' arm span, it's relatively easy to hold the one end in place
while you carefully fit the rest of the board and push it down onto the
tongue.

Once the new board is fully engaged onto the tongue of the preceding
board, use a small T&G scrap and a hammer to make sure it is seated
tightly. I also tapped the end of the board so it made a tight joint
against the next board.

is it better to randomly space joints or have a set pattern.

We practiced with the T&G boards in our garage attic before doing our
house. In the garage I made all the joints line up with the rafters,
making sure there were at least two rows of boards between each vertical
joint. Lining up with the rafters produced a lot of waste material.

So on the house we just installed the boards randomly. We used #3 lumber
to save money, and cut around the knots and splits to end up with good
boards. Of course, this left us with many random lengths, so our ceiling
ended up random too. It worked out very well, with much less waste.
Again, just stagger the joints as much as possible, and try to avoid
lining up vertical joints if you can (at least one full row between
joints).

one board is 10' and the one joined at its end is 8'. Then the row
next to them is a board 8' joined by one 10'.

Assuming you're working with 10' boards, go across the ceiling, then use
whatever scrap you have from a row to start the next row (the same way
hardwood floors are installed). If you end up with a joint too close to
another, cut the board back a foot or two, and use a full board to span
the joint. Use the cutoff farther along in the ceiling somewhere.

A few tips I learned along the way...

1. Bring the lumber into the room you are installing it in, and let it
sit there a couple of weeks before you install it. This will let it
"Acclimate" to the moisture levels in the room. I failed to do this with
the last load of boards we received, and once the heat from our woodstove
dried out the boards, they started shrinking. It's high enough on our
ceiling that it's hard to notice, but it's not something I would want
down where I'd see it.

2. Don't use a board that is warped. Take my word for it, the warp will
only get worse as the wood dries out...

3. Bevel the ends of each board at a 45 degree angle, rather than just
butt the boards together. Wood doesn't shrink "much" lengthwise, but it
will shrink enough to open up the gaps in a simple butt joint. By
overlapping the bevels of boards, the joint can open and close with
varying moisture levels without leaving a noticeable gap. And, it
provides a marginal bit of extra support too.

4. If you can finish the boards before installing, do it. We brushed
polyurethane on our ceilings after installation, and despite our best
efforts, nearly always had poly running down our arms and onto the floor
(new construction, so no harm done, but it was messy).

5. I used a 15 gauge air nailer to secure the boards. Put a nail at every
rafter/joist, aiming at a 45 degree angle where the tongue meets the top
of the board. Then the next board will cover the nail holes so there's
nothing to fill (again, just like installing a hardwood floor).

Have fun!

Anthony