It can seem, these days, that no self build or renovation is complete without a swathe of glazing somewhere in its design. And for good reason — who wouldn’t want the option of opening up their home to the great outdoors when the sun shines, adding what effectively becomes another living space, and to flooding their interiors with natural light?

But bi-folds can be quite an investment — and a confusing one at that. There is a huge choice of materials, glazing options, operating systems and optional extras to be taken into consideration, and knowing which one offers best value for money and will work with the design of your home – both in practical and visual terms – can feel a bit like a gamble.

Shop our selection of bi-fold doors and find the right design for your project

Which is better for bi-fold doors: timber or aluminium?

Timber bi-folds are beautiful and certainly a fantastic option for those creating a traditional-style home or adding them to a period property. However, do be careful when choosing between the different timber options. Engineered timbers are ideal as they have more dimensional stability than solid timber doors. Although softwood engineered products are available, which are cheaper than hardwood, some of the lower-end models can still be prone to warping over time when exposed to heat and moisture, meaning they will stick in their frames or won’t close.

“Bi-fold doors made from wood give a traditional appearance as well as having the natural beauty of a living material. The downside is that they require regular painting or varnishing to maintain their appearance. Typically, wooden doors provide the best thermal insulation, though,” advises Peter Watkins, General Manager of Centor Europe.

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These Kloeber aluminium Kustomfold bi-fold doors measure 2,090mm high by 1,000mm wide

“Aluminium does have the distinct advantage of slimmer sightlines and a powder-coated finish, which will never have to be re-coated,” adds Matt Higgs, Sales Director at Kloeber. “Aluminium bi-fold door panels can be made wider than timber doors so can sometimes be more cost-effective due to needing fewer doors within the frame.”

How much will they really cost?

As with all window and door products, this varies hugely on size, material and quality.

“For a standard height door you should expect to pay around £1,200 per linear metre of overall frame width for a good-quality, well-engineered system with a good spec of glass and ironmongery,” says Matt Higgs of Kloeber.

You will also need to factor in VAT and installation costs to the total price, and possibly delivery. Some companies will ask for a deposit on ordering, with the full amount payable on installation or delivery. A three-panel door like the one above might typically cost in the region of £4,000-£5,000.

“A bi-fold door has many aspects as well as price that should be considered before making a choice. It is important to look closely at a company’s history, warranties and the general quality of the products. Ask about adjustment; aluminium expands and contracts with climactic change — can the system cope with this movement? Never buy a bi-fold without seeing it first; there’s no substitution for seeing and operating the product for yourself,” warns Matt Higgs.

How big (or small) can I go?

“Hardware systems have maximum individual panel weight, width and height restrictions,” says Peter Watkins of Centor. “Panel weight is affected by the size and type of glazing used. Standard aluminium panels can be double or triple glazed, 1,000mm wide and 2,800m high, while wooden doors can go higher, with specialist systems up to 4,000mm high and 1,100m wide. You can have up to 16 panels in one frame depending on the accuracy of manufacture and tolerance.”

For Kloeber’s bi-fold doors, for example, which are available in both aluminium and timber, panel widths can be up to 900mm for timber and 1,200mm for aluminium, with a maximum number of 12 panels overall.

How do you go about getting flush thresholds right?

The best thresholds between inside and out are the ones you don’t notice. Rain penetration can be an issue, particularly on exposed south- and west-facing walls. The answer is a correctly installed rebated, weather-tested threshold.

“We offer several different types of threshold for different purposes,” says Kloeber’s Matt Higgs. “Each door has a threshold at the bottom and this part can be dropped down so your finished floor inside lines up with the top of the threshold. Sometimes this may mean taking out a course of bricks under your existing aperture. There would usually be a small difference, say 20mm, between the internal and external floor heights to ensure a fully weathertight seal.”

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Bi-folds are usually specified for their ability to merge inside and out (as in this instance from Origin) — but make sure the threshold is as level as possible

What is the best method for screening bi-fold doors?

The simplest solution is to opt for full-length curtains, but this is an unpopular choice as it blocks some of the light coming in even when the curtains are open, and somewhat distracts from the sleek look offered by bi-folds.

“It is possible to buy glazed units with built-in venetian blinds, which give a satisfactory solution but partially obscure the glass. Vertical blinds are either housed in a unit on the wall or built into the ceiling, but hinder access from inside to out,” explains Centor’s Peter Watkins.

“Built-in screens and shades that move horizontally (as with Centor’s integrated doors) provide a good solution. Insect screens offer protection when the doors are open, and their shades provide protection from harsh sunlight and offer privacy when the doors are closed. The screens and shades are drawn from the door jamb when needed, move aside for access, and retract when not in use.”

What is the best operating system?

When choosing bi-folds there are two terms you will come across: ‘top hung’ and ‘bottom rolling’. This refers to the way the weight of the door is supported. Advice varies on which is best, but bear in mind that top-hung doors conceal the bulk of the operating mechanisms in the frame head, plus dirt and leaves are less likely to become lodged in the top track, unlike the bottom track, where it can affect the running operation. On the downside, top-running systems do require a sufficiently strong lintel or beam above the opening to take the weight of the door(s).

“Bi-fold doors require hardware systems with a greater capability than sliding or hinged doors because of the moving forces and loads that occur during door movement,” says Peter Watkins of Centor. “Look for systems specifically designed for bi-fold doors, with wheels that run in flat tracks. These give smooth operation when compared to grooved wheels on a raised track.

“Horizontal and vertical adjustment is important as any inaccuracies in either manufacturing or frame installation will be amplified on larger doorsets. Systems hinged directly onto the door jamb have restricted adjustment, so the most adaptable systems have pivoted end doors.”

If you are looking for advice on the different designs, styles and trends for bi-fold, french and sliding doors CLICK HERE

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