Bifold Doors

Bifold doors run on rollers along a track, either top-hung with the weight carried by the head or bottom-rolling with the weight on the threshold. Top-hung systems depend on a strong, stiff lintel or steel above, so the glazier checks support before ordering, because sagging heads cause doors to bind.

The number of panels sets how the doors open. Odd numbers, such as three or five panels, usually include a traffic door that opens on its own for everyday use. Even numbers can split to both sides. Panels can fold inwards or outwards, and outward folding keeps the room clear.

Bifold door panels have wider frames where they meet than a sliding door, because each panel needs its own frame and hinges. A five-panel set shows four vertical sightlines when closed. If the view matters more than a fully open wall, a sliding door may suit better, so compare both.

Aluminium is the usual material for bifold doors because its strength allows slim, stiff panels that hold heavy double or triple glazed units without distorting. uPVC bifolds cost less but have bulkier frames and suit smaller openings. Engineered timber bifolds offer a natural finish but need periodic re-coating.

Thresholds range from a raised weathered sill to a low or flush threshold for level access between floor and patio. Low thresholds rely on drainage outside, such as a slot drain, and some shelter from driving rain. The right choice depends on exposure, patio levels and how the doors are used.

Bifold doors are glazed down to floor level, so every pane needs safety glass. In England, Approved Document K treats glazing in doors within 1500mm of the floor as a critical location. Units are usually toughened, with laminated glass added where extra security or protection against falls is wanted.

In England, replacement doors with more than 60% of the internal face glazed should achieve a U-value of 1.4 W/m²K or a Doorset Energy Rating of band C under Approved Document L. New openings in extensions are assessed with the whole extension, and large glazed areas may need energy calculations.

Security on bifold doors comes from multi-point locks on the traffic door, shoot bolts top and bottom on the folding panels, internally glazed beads, anti-lift track design and hinges that cannot be removed from outside. Ask whether the system has been tested to PAS 24 and fit an anti-snap cylinder.

Bifold doors take longer to manufacture than standard doors because each set is made to the opening and coated to order. Fitting a typical set usually takes one to two days, depending on width, removal of old doors and any making good to plaster, flooring and the patio outside.

The price of bifold doors depends on overall width and height, the number of panels, material and profile system, colour, glass specification, threshold type and the condition of the opening. Wide or very tall sets and triple glazing add cost. See the guide prices for typical ranges; the written quote fixes your figure.

Bifold door tracks need keeping clean: vacuum or brush grit from the bottom track and drainage slots regularly, wipe frames with mild soapy water and lightly lubricate the locking points. Panels that drag or catch usually need adjustment at the hinges or rollers, which a glazier can carry out.

Creating a new bifold opening in an external wall is structural work that needs building regulations approval and a correctly sized lintel or steel beam. Replacing existing doors in the same opening is simpler. Planning permission may also be needed for new openings in listed buildings, flats or conservation areas.