How do I fix tongue and groove (T&G) flooring to Boxspan?.

The best way to fix T&G flooring to Boxspan is to fix particleboard down first and then glue and nail the T&G boards to the particleboard. The reason for this form of fixing is that the nails and screws used to fix to Boxspan have quite large heads. This method is now often used even when fixing to timber joists because of the following benefits:

Fewer joists as you do not need to put double joists under each parallel wall.
Construction is easier as floor is in place over joists.
Less T&G used, as boards can be end matched (they do not have to start and finish on a joist).
Considerably better sound and heat insulation.
T&G much less affected by changes in moisture under the house, which can cause serious damage to T&G floors.