Small building erector

Lusk:
What would be the tacho rules for somebody who drivers a 7.5 tonne vehicle to transport a small building from their home base to a customers, erects the building and then drives back to base?

You’re transporting the building to a customer so presumably you’re talking about a commercial transaction, therefore it’s in-scope of EU regulations.

I think you already know the rules but just in case I’m wrong see this post.
viewtopic.php?f=5&t=123738&p=1924193#p1924193