I recently had some bi-fold doors fitted in the dining room and I'm about to work on the floor in the same room.

I find the fitting methodology of the bi-fold company questionable.

First, a damp course membrane across the threshold, which has abundant silicone applied underneath to seal the underside. They then put the sill base on this membrane.

What your left with is a protruding damp-proof membrane on the inside that you'll trim to about an inch, apply silicone and then bend it up to make contact with the inside of the threshold. You then put down your flooring, which covers things up. Not convinced by that at all.

What I was thinking is to leave the damp proof membrane flat on the inside and apply a hefty silicone bead along the sill base to seal it to the membrane. Then maybe apply some flashing tape at 90 degrees in the angle to add a further seal.

I'll only get one shot at this, so any advice is appreciated.

Thanks