Patio, French, bi-fold and balcony doors

French doors open outwards or inwards on hinges and suit narrower openings. They need clear space to swing and are the traditional choice for older houses. Sliding patio doors keep one panel fixed and slide the other behind it, so they take no room to open and give large panes with fewer frames. Lift-and-slide versions carry heavier glass more easily.

Bi-fold doors concertina to one side and open the whole width, which is why they are popular on rear extensions. The trade-off is more frames when closed, more moving parts, and more joints where weather and wear can take their toll. On an exposed elevation facing prevailing wind and rain, a well-made slider can be the more reliable choice.

GOV.UK lists external doors with less than half of their area glazed among works that do not need Building Regulations approval. Patio, French and bi-fold doors are mostly glass, so their replacement is controlled work: either an installer in a competent person scheme such as FENSA or CERTASS certifies it, or Building Control approves it.

Safety glass is required in critical areas, and the Planning Portal summarises these as any glazing within a door up to 1500 millimetres from the floor, side panels close to a door up to the same height, and other glazing up to 800 millimetres from the floor. In practice, patio door glass is toughened or laminated throughout. The doors also have to meet the thermal standard for replacement doors.

If the door is the main entrance of a home built since 1999, the Planning Portal points out that a level threshold must not be made worse. For a rear door this is not the same legal point, but a level or low threshold is still worth considering for anyone who uses a wheelchair or pushchair.

Source: planningportal.co.uk

Widening a window into a door opening, or knocking through for a set of bi-folds, is structural work. A new lintel or steel beam has to be designed and installed, Building Control has to approve it, and on a party wall or near a neighbour's foundations the Party Wall etc. Act 1996 may apply. The door company may not be the right business to design that part.

Upstairs, a Juliet balcony, which is a guard rail across a full-height door with no platform, is normally permitted development according to the Planning Portal. A true balcony you can step out onto is different: balconies, verandas and raised platforms often need planning permission, and the Building Regulations cover the structure, the guarding height and fire safety. Raised decking outside patio doors can also count as a raised platform if it is high enough, so check before building up to the threshold.

Source: legislation.gov.uk

Water collects at the foot of a door. A low threshold looks good, but it relies on the patio or decking outside being set below the door with a drainage channel or fall away from the house. If a new door sits flush with a paved area that falls towards it, rain will find its way under the frame.

Ask about the locking system, anti-lift protection on sliders and bi-folds, laminated glass, and hinges that cannot be removed from outside. The formal security standard in Approved Document Q applies to new dwellings, but the same features are sensible on any ground-floor door.

• door type, number of panels, opening direction and traffic door
• frame material and colour, and whether the frame sizes suit the opening
• glass: safety glazing, energy rating and any solar control
• threshold height and how the outside surface drains
• locking, anti-lift features and hardware
• any structural work, who designs it, and certification of the doors

The job description, not your identity, is shown to window and door companies near you. When a company buys it, that company pays Offrano, and the request is no longer available to others. We first email you its name, address and phone number, and only then does it see your details. It costs you nothing.

Nobody is obliged to take the request; after 21 days without a buyer it is withdrawn. You can decline the quote. Offrano only checks that the buyer is a registered business, so ask to see installed doors and check its competent person scheme membership.