Just purchased our top quality Bi-fold doors? One thing to note, Bifold door sizes are inclusive of a top track, we have had numerous instance of joiners discarding this item and fitting the doors only to discover the doors look undersized, here's some extra detail.
Use the same measuring techniques as mentioned in "How to fit an Internal door" and be aware that in most cases there are locating pins to the top and bottom of most bifold doors.
All quoted sizes on this site are to suit "openings" of that size, the door kits are always smaller by about 10mm in width and height to allow the correct operation of the Bi-fold track and associated hinge pins, where we state that these doors are supplied in "Kit Form" we can assure you that the glass or panels are always fitted in the doors and the doors are hinged together to form a Bi-fold pair.
We believe that bi-fold doors are very easy to install, just make sure you fit the top track as level as possible and that you do not force the hinge pins into any Pre-drilled hole in the door or indeed into any holes that you have to drill in the door to allow for those pins, use a bit of "soap" if these pins are really tight and then use a large amount of common sense.
Please don't be surprised that a bi-fold door is smaller than the opening in height and width, the way these doors "hinge" requires more clearance than a normal hinged door, they also require clearance top and bottom for the "pins" and the sliding track.