Folding sliding doors are best left to the experts. Too many corners have been cut in recently launched systems. A common failing is the use of either a top or bottom running track but not both.
Some timber systems do not use engineered timber, causing it to warp and expand and some aluminium systems only use profile with a 1.5mm wall and a thermal bridge that does not conform to the new thermal regulations (u-values). The products may look nice and operate wonderfully in the showroom. However, these design omissions can compromise the effectiveness, security and operating limits of the system.
Many companies may say "What do they know that I don’t? I've been in the window industry for over 30 years". They may have been in the window industry for a long time, but they have only recently started manufacturing folding sliding doors.
To specialise in one particular field of the glazing industry is to have accurate knowledge and skill in that field. The term folding sliding door specialist is used so flippantly by companies that also manufacture windows, French doors, sliding patio doors, roofs and conservatories.
There are many upvc and joinery companies that believe that they can simply manufacture some rectangle panels, fit some hardware on them that they purchase from their hardware supplier and call themselves a folding sliding door specialist.
There are many upvc and joinery companies that have had to product change or diversify into folding sliding doors because the industry they are in is financially compromised.
Some window companies have even setup a new subsidiary just for this product.
Customers need to be aware and not be fooled by speculators and chancers wanting to make a fast buck, only really interested in selling plastic profile.