I notice that you quite openly promulgate the following
“The fact that NHBC now requires that raised decks are built in accordance with the TDA Code of Practice is in itself acting as a door opener for TDA Deck Mark quality accredited installers.”
I have spoken to NHBC and they can confirm that indeed “anyone” can install decks to this standard, as long as they meet this standard. They also clearly state that you don’t have to be a TDA member to adopt this standard.
My second point is that where on this planet do you find a product that would be able to realisticly uphold a 60 service life, timber joist would certainly not, even most hardwoods would struggle? Code of Practice:08/01 refers
A fair question I feel, I would rather not just simply have a standard for standards sake unless it made sence and the reasoning for it had a sound technical explanation.