If you're choosing bi-fold doors, you need to choose big.

Unlike French windows and sliding patio doors, bi-fold doors consist of three or more doors that fold back on themselves and sit flat against one or both walls, depending if they open in the middle or at the side.

There’s no way around it - they look at their most spectacular spanning a whole wall, or even walls, and when the weather’s nice, you can fold them back to open up the most stunning entertaining space.

The cost of the doors will vary depending on the size of the opening, whether the doors are a standard size or made to measure, and what they’re made of (typically wood, UPVC or aluminium).

Companies that make bespoke bi-fold doors often install them and provide a guarantee, giving you convenience and peace of mind.

Bi-fold doors are most effective when the floor and ground level on either side of them is the same. This may involve some work in the garden, but it will improve the indoor-outdoor flow and increase the ‘wow’ factor, especially if you use the same, or similar, flooring inside and out, perhaps slate tiles. Inside, the new doors may mean you have to replaster, redecorate and move things, such as radiators, sockets and switches, but planning permission isn’t usually required.

That said, there are exceptions. For example, planning may be needed for homes on ‘designated land’, such as conservation areas – check with your local council if in doubt.

If your home is listed, you’ll need listed building consent from the council to fit bi-fold doors, and if you live in a leasehold flat or house, you may need the freeholder’s permission.

If you fit the doors yourself, or get a builder to do it, it’s vital to get the work checked and signed off by a building control inspector, either from your local council or a private firm, to ensure it complies with building regulations. The easiest option is to use a window and door company that can self-certify their work complies, such as companies belonging to FENSA (fensa.co.uk).

Either way, you’ll need a building regs certificate for the doors, otherwise you may have a problem when you try to sell your home. Unless you have an existing window/door that’s the same as, or bigger than, the size of the opening required for the bi-fold doors, a new lintel will have to be fitted above the opening for support.

Your first step (at the planning stage) should be to consult a structural engineer, or use a reputable window and door company to supply and fit the doors.

It should carry out a survey and then do whatever’s necessary to make your home structurally sound.