In the recent post on reclaimed floorboards there seemed to be some
confusion over when tongue & groove floorboards became availiable. My house
which consists of an 18th century stone cottage modified in the 1850s
(extended backwards and upwards) contains original wooden floors from both
periods. The 18th century boards being 9inch wide T&G and the later being
around 5inch T&G. I researched through some of my literature on period
houses and apparently the first floorboards were hand sawn and as such had a
"nearly" square edge. Mechanisation in the 18th century enabled production
of "proper" square edge boards and T & G. Both were introduced at roughly
the same time.
So there you have it - T & G has been around as long as the machine produced
square edge boards - 18th Century.