Thank you all for your comments which have been helpful and I'm sure a survey is very good advice. As I said the steel pontoon is a new ballgame...
I'm probably being a bit girly and inexperienced about steel pontoons but this is how it was stated on the details. Note. There is a 'cellar'...
Can anyone help. Been to view a houseboat constructed on a steel pontoon. The pontoon contains lighting wiring and plumbing which I was OK with....