Next job in the never ending book is tiling the floor of the front
extension (finished screed at the moment) and continuing along the old
hall and into the shower room which are/were Khars engineered wood laid
on green chipboard.

Both floors have UFH, between joists on old section and in-screed on new
section.

We've got "wood effect" porcelain "planks" which are going to be laid in
a herringbone pattern apparently but the question is, should either the
screed or the waterproof chipboard need sealing (SBR I'm guessing) to
keep tile adhesive workable for longer?
Also, where the screed meets the old hall/doorway and goes to chipboard
should I create a junction between surfaces to allow for the different
UFH zones and different heat-up/expansion rates between floors etc.

Cheers
Pete