On 6 Jul, 21:52, "George" wrote:

Er! probably as it was made to order ie it was an expensive material in
1922.

It wasn't (relatively). Plasterboard started being used commonly
around 1916, owing to shortage of labour to do wet plastering. It
might have been "expensive" as a _material_ in 1922, but then so was
plastering. Overall the balance had switched to "expensive materials /
reduced on-site labour" and never really switched back again, even in
the '30s.