We have a 35,000 sq ft roof with an EPDM system installed over 1/2" fiberboard which was installed over an original BUR. Our question is, can the EPDM and fiberboard be removed down the the existing BUR and then have a new EPDM/Fiberboard system installed over it? Or do both systems need to be removed?
If the bur is tight and smooth and you have good solid screwing I don’t see why not, as long as it is good and dry. If the fiber board you are taking off is wet the bur likely has water trapped in it which will not dry out once the new epdm is instated. What kind of substrate is the bur adhered to?
Steel decking/insulation. The existing fiberboard appears to be dry and solid
You are looking at a drastic increase in cost to remove the bur and insulation over the steel deck opposed to go over it. Honestly on a job that size And cost I would be Consulting with an engineer not asking guys like me on a forum. Here is a good place to start, but I think you probably want a stamp on that recommendation.
I would simply Remove exisiting perimeters
Cut, Slice some in the field and against any walls.
Then install 1/2 on top of it and go…
Are you getting a permit? Code does limit you to 2 roofs, but you can easily do as RL says and slice up the membrane, even cutting it so you remove a large portion of it between the fasteners and probably get past the inspector.