These 8 to 12 inch wide boards were nailed together tight.
1x6 tongue and groove roof sheathing.
With less than 4 supports a special pattern requiring specified lengths must be used.
Wood is an excellent insulator and in moderate climates no additional rigid insulation on the roof is necessary.
4 tongue and groove roof decking.
Tongue and groove commonly used as roof sheathing where a ceiling will not be installed and they will be visible from inside the house such as across beams in a vaulted ceiling.
Tongue groove boards.
This arrangement is applicable to 4 or more supports 3 or more spans.
Tongue and groove boards were used for decades prior to the widespread adoption of plywood as a sheathing material in the 1950s and 1960s.
But as it is tongue and groove the load will also be transferred over the adjacent pieces.
Tongue and groove boards have a wide range of uses from ceiling paneling to accent walls and wainscoting.
When the roof was first nailed on of course all the nails were in solid wood.
In my experience the need for tongue and groove or edge clips is determined by the thickness of the roof sheathing and the spacing of the rafters.
But the lumber was not usually kiln dried.
Old houses with asphalt shingles usually had either tongue and groove boards or straight sided boards abutting.
Perfect for interior or exterior projects boards are light weight and easy to nail saw trim or cut.
The keyword here is solid it used to be standard to use shiplap 1 boards tongue groove or other boards for the roof deck.
For 5 8 or thicker roof sheathing on 16 o c.
But you re going to have to do some of the load math to figure out what the exact load will be on one piece of the tongue and groove.
Rafters it shouldn t be an issue.
Roof deck 2x6 or 1x6 t g we use 1x6 up to 3 but the roof is then strapped after with 2x4 then sheathing.
All pieces are supported on three supports.
The main reason to use tongue and groove boards these days is appearance from beneath the roof.
Some use clips as convenient spacers.
As wood dries it shrinks.
All end joints occur in line on every other support figure 6.
On 24 1x6 will work but put a layer of sheathing down to eliminate the roofing nail issue.