Cortizo Aluminium Bifold & Sliding Doors

Cortizo Bi-Fold Plus

The Bi-Fold Plus runs from one to 14 sashes, opening inward or outward, in odd or even numbers. Opened outward it will also turn a 90° corner with no mullion in it, so two elevations of glass meet at a corner that folds away with the doors. Very few folding systems sold in the UK will do that, and it is the reason we specify it on corner extensions where a fixed post would have killed the design.

Each sash takes up to 1,200mm of width and 3,000mm of height at a maximum of 120kg, with 80mm sightlines on frame and sash and glazing from 25mm to 48mm. The thermal figure comes from a 45mm polyamide strip running through the frame and the sash, not the frame alone, which is what takes it to 0.78 W/m²K on Cortizo's reference build. Tested at 3.73m by 2.50m over three sashes it returns Class 4 air permeability, Class E750 water tightness and Class C3 wind resistance.

The U-value question, answered honestly

Here is a caveat we give in the showroom that most quotes will not. The 0.78 W/m²K figure is Cortizo's best case, tied to a specific typology, size and glass unit, and Cortizo's own technical file says exactly that on the front page. Direct Window Supplies, who fabricate the system here in the UK, publish the same door from 0.87 W/m²K.

Neither number is wrong. They describe different builds. In our experience the figure worth planning around is the one your surveyor calculates for your actual opening and your actual glass, not the headline on a brochure. A wide door with big panes and a small ratio of frame to glass will land near the best case. A narrow door with lots of frame in it will not, whichever brand is on it.

Cortizo 4700 In-line Slider

The 4700 runs on rollers and carries up to 280kg a sash. Sashes reach 2,500mm wide by 3,000mm high with a 50mm sash sightline, so on a five-metre opening you are looking at two panels and a single vertical line of aluminium through the middle of the view.

In our experience the two headline maximums are the thing worth understanding, because they do not combine. A sash at the full 2,500 by 3,000 is seven and a half square metres, and at that size the glass on its own accounts for most of the 280kg the gear will carry before you have added the frame. Push toward the biggest panes and the glazing specification stops being a free choice. We have found this is where quotes diverge most, because two firms can quote what looks like the same door and only one of them has worked the weight backwards from the gear.

Air permeability is Class 3 and wind resistance Class C5, both measured on a 1.8m by 2.2m two-sash panel. That is worth knowing, because a five-metre door is more than three times that area and test classes do not scale with size. Water tightness is Class 7A and acoustic performance runs to Rw 40dB with the right unit. Glazing is 26mm to 36mm. Cortizo's system allows 2, 3, 4, 6 and 8 sash layouts across up to four rails, including pocket sliders that vanish into the wall, but Direct Window Supplies fabricate to six sashes, so six is the number to work to on a UK order.

Bifold or slider?

In our experience, the Bi-Fold Plus works better than the 4700 on openings under four metres because you get the whole aperture back and the thermal figure is stronger, 0.78 against 1.0, on the back of a 45mm polyamide break against the slider's 20mm to 25mm.

Past four metres it flips. A five-metre bifold is five one-metre panels plus a stack of aluminium parked somewhere, and that stack has to live against a wall or a return. A five-metre 4700 is two panels, one line of frame, and a view you cannot get any other way. We have found that people who arrive certain they want to fold the whole thing back tend to do it through the first summer and then settle into leaving it part open, which is worth being honest with yourself about before you commit the budget.

What the running gear has to survive

The master sash on a Bi-Fold Plus is the one you use as a normal door every day, and it is tested to 50,000 open and close cycles under UNE-EN 1191. Use it ten times a day and you are past thirteen years before you reach the test figure. The remaining sashes, which in practice move a handful of times a year, are tested to 25,000.

Profiles are extruded in 6063 T-5 alloy, 1.8mm thick on the folding door and 1.5mm on the slider. Both systems have passed PAS 24 security testing, the Bi-Fold Plus over three sashes at 2.70m by 2.50m and the 4700 over two sashes at 2.40m by 2.40m.

Colours, finishes and fabrication

Powder coating is to Qualicoat standard at over 60 microns, in any RAL shade, mottled or textured. Dual colour is available across both systems, so the outside can be anthracite and the inside can be white without a compromise either way. Wood effect coating is to the Qualideco standard, and anodised finishes run to Class 15 as standard with Class 20 and 25 available on request.

Cortizo is a Spanish systems company, but the door that arrives at your house is cut, machined and assembled by Direct Window Supplies in Swindon, roughly 35 miles from our Cheltenham showroom. DWS are purely a manufacturer and do not install, which is their own stated position, so the people building your doors are not also quoting against us for the fit. From working with clients we have found lead time and remake time are what people actually feel on a job, and a short supply chain is worth more on both counts than a longer one with a better story attached.