Bi-fold doors: all your questions answered
From how to choose the best frame material for your bi-fold doors to key design considerations, we have all your questions answered
What are bi-fold doors?
Bi-fold doors provide a spectacular finishing touch to a renovation project or new extension. They're comprised of two or more glazed, hinged panels, which allow an entire wall to be opened up, filling rooms with daylight and effortlessly connecting inside and out.
Good quality bi-folds are a big investment, so take time to consider panel and aperture sizes, materials and configurations, and look into manufacturers and suppliers, so that you can make the right choice for your home and budget.
Which is best – bi-fold or sliding doors?
Both types of doors have their pros and cons so work out your priorities. Pulled right back, bi-folds expose up to 90 per cent of the aperture, giving an unobstructed outlook, whereas sliding doors open to a maximum of 70 per cent - and just 50 per cent if there's only room for two panels. Starting at around £500 per square metre, bi-folds are less expensive, but sliding doors allow for more minimal framing and wider expanses of glass, so the view is less interrupted when they're closed - as is the case for most of the year.
What's the best frame for bi-fold doors - wood, composite, aluminium or uPVC?
There are several options for the frame. sustainable hardwood adds character and warmth for a period property, like a Victorian or Georgian house, although it needs painting or varnishing from time to time or it will start to deteriorate. If you don't relish the regular upkeep, a composite - comprising of a timber frame with an aluminium exterior - is a low maintenance alternative.
Slimline aluminium also requires minimal care and has become the go-to material for contemporary frames as it's super strong and can support larger glazing panels than timber, reducing the number of sightlines. uPVC is more price friendly but isn't as durable as wood or aluminium, and frames need to be thicker.
Bi-fold doors can be either double or triple-glazed, though the latter isn't necessarily more energy efficient.
What you need to consider before installing bi-fold doors
Most bi-fold doors open outwards so they don't encroach into the living room, though if space is tight - for example in a narrow terrace - check there's enough room for them to fold back fully.
Opt for the smallest number of panels as possible bearing in mind that the maximum panel width is about 1.1 metres, although this varies according to the height, frame and glazing.
Think about incorporating a traffic door - a single panel that opens independently to access the garden easily - and ensure the bi-folds are completely weather resistant by fitting a rebate in the doorway. A rebate is a narrow upstand which prevents moisture leaching inside and can be sunk below floor level so that the threshold is virtually flush.
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How do you install bi-fold doors?
Your bi-folds must be professionally installed, so if this service isn't provided by the supplier as part of a package, find a FENSA-approved installer Depending on how their weight is supported, bi-folds are either bottom rolling or top-hung. While a bottom rolling system runs on a track set into the floor, with a top-hung system you don't have to worry about dirt getting trapped in the base and affecting the smooth operation.Plus, the mechanism can often be concealed in the frame for a neater finish. However a new lintel or steel beam may be required to cope with the load, so seek advice from a structural engineer.
Are internal bi folding doors a good idea?
Far from being only suitable for external use, bi-fold doors make practical and stylish room dividers. Bi-fold doors are particularly effective in open-plan layouts where an internal wall has previously been removed to create a double living room or a combined kitchen-diner.
Adding a set of bi-fold doors will enable you to switch the area back into two cosier rooms when you need to, reducing noise levels and giving you greater privacy. solid doors provide complete separation but obstruct the flow of light when closed, whereas fully or partly glazed doors keep rooms bright and let you keep an eye on the kids.
Andrea Dean is a journalist specialising in property, lifestyle & interiors