Bifold doors: what to know before you buy

Panels, folding and stacking

More panels means narrower leaves and more frame showing; fewer panels means wider leaves and more glass. Think about where the stacked doors will sit when open, inside or outside, and whether they will block a path, a radiator or furniture.

A traffic door, a single leaf that opens on its own, is worth having on external bifolds so you do not have to fold the whole set to step outside.

Thresholds

External bifolds come with standard or low thresholds. Low thresholds give a near level step between inside and out but need careful drainage outside to keep water away. Getting the internal floor level and external paving right at the design stage avoids a trip step or water ingress later.

The opening matters more than the doors

Bifolds need a square, level, plumb opening to run smoothly. If an existing opening is being widened, a new lintel or beam is usually needed, which may require building control involvement and structural calculations. A structure that deflects even slightly can make the doors bind.

Internal bifold doors

Inside the house, bifolds let two rooms work as one open space or be shut off for warmth and quiet. They are lighter than external doors and do not need weather seals, but still need a solid head and a level floor. They also suit wardrobes and utility cupboards where a swinging door would get in the way.

• Check which way you want the doors to stack before ordering.
• Leave space for the stacked leaves when open.
• Consider floor finish at the threshold before fitting.

Frame materials and glazing

External bifolds are most often made in aluminium, uPVC or timber. Aluminium allows slim frames and large panels; uPVC is usually the budget option; timber looks warm and suits period homes but needs refinishing over time. Whatever the frame, check the glazing specification, locking points on every leaf and the quality of the running gear, because these decide how the doors feel to use after a few years.

Large areas of glass affect heat and light. A south facing set can make a room hot in summer, so blinds or solar control glass are worth considering, while a north facing set may need good insulation values to keep the room comfortable in winter. Blinds that fit between or onto the leaves are easier to plan before the doors are ordered than after.

Ask about lead times and what happens on fitting day. External bifolds are usually made to measure after a survey of the finished opening, so any building work on the opening needs to be complete and accurate before the final measure is taken. Fitting then involves setting the frame dead level, fixing it securely, sealing it to the wall and adjusting every leaf so the set folds smoothly and locks firmly.

Questions we're asked about this