Terrace door

Terrace doors differ primarily in how their panels move. There are three opening principles commonly used in terrace door design: pivot, sliding, and folding. These principles determine the maximum opening width, the space required by the terrace doors within and adjacent to the room, and the final glass area.

Rotating: The classic tilt-and-turn door

Tilt-and-turn doors are standard in most existing buildings. One or two leaves swing into the room like an interior door and can also be tilted. Their width is limited because the entire weight of the leaves is suspended from the frame by the hinges. Furthermore, space must always be kept clear in front of the door for the swing area, which restricts furniture placement. This design quickly reaches its limits when it comes to creating a spacious, open terrace entrance.

Sliding: More glass, no swivel range

With sliding systems, the glass panels slide in a straight line from one side to the other. This allows for larger formats and keeps the space in front of the terrace door clear. The SUNFLEX sliding window systems SF40, SF60, and SF80 are particularly slim: the frame is only 21 mm wide, the glass area reaches up to 98 percent, and surprisingly wide installations of up to 13.8 meters are possible. What remains is an unobstructed view of the garden.

Folds: Open the front completely

With a folding sliding door, the panels are connected and fold to the side like an accordion. This is the only design suitable for terrace access that completely eliminates the transition between living space and terrace: In summer, two rooms become one. Sufficient lateral space for the folded panels is required. The SUNFLEX folding sliding door systems SF45, SF55, SF55e, and SF75 are the only product family in the range to cover all insulation levels, from uninsulated to highly insulated.

Special form: The sliding-rotating system

In addition to the three basic principles, there are hybrid systems. With the SUNFLEX sliding-folding system, each sash is individually rotated outwards and then slid to the side. This allows the front to be opened almost completely. For corner configurations, loggias, and tight floor plans, this is often the best solution. Its second strength lies in weather protection: The SUNFLEX sliding-folding system makes loggias and balconies usable in wind and rain without obstructing the view. For replacing an exterior wall on heated living spaces, however, thermally insulated sliding window or folding-sliding systems are the right choice.

There's rarely a one-size-fits-all solution for a perfect terrace door. Depending on your living situation, architecture, and personal preferences, very different questions arise. The following sections will show you which considerations are important for different situations.

New construction: Planning the terrace door correctly from the start

Anyone building a house has the rare opportunity to design their terrace access without compromise. To ensure this opportunity isn't wasted, it's worth clarifying the following points early on:

Opening width and rough opening dimensions

The width of the wall opening should be determined before the rough construction and plastering work begins. Subsequent changes to a load-bearing wall are complex and expensive. Discuss the desired width of your glass front with your architect, structural engineer, and SUNFLEX specialist partner early on.

System selection and opening type

Whether folding sliding door, sliding door, or sliding-folding system: each type of opening has different requirements for the building structure and the subsequent installation. A sliding door requires no swing space at all. A folding sliding door needs some space to the side for the parked position of the panels.

Plan for zero threshold 

A barrier-free design with a recessed floor track should be planned for in the floor construction from the outset. The track requires sufficient installation depth. Retrofitting is possible, but more complex.

Thermal insulation and Uw value 

New buildings typically have high energy efficiency requirements. Coordinate the glazing of your terrace access with the building's energy concept. The Uw value describes the thermal insulation of the entire window unit, including frame and glass: 
the lower the value, the better the insulation. For low-energy and passive houses, we recommend the highly insulated SF80 sliding window system, which achieves Uw values ​​from 0.75 W/m²K, or the highly insulated SF75 folding sliding door. The specific Uw value of the SF75 depends on the glass selection and unit size and will be calculated by your specialist partner for each project.

Burglary protection

Ground floor terrace access points should be lockable to ensure homeowners feel secure. For new buildings, at least resistance class RC2 is recommended, the European resistance class for burglar resistance according to DIN EN 1627. This is achievable with the SF60 and SF80 sliding window systems and optionally with the SF55 and SF75 folding sliding systems.

Terrace doors in existing buildings: Modernization that pays off

Replacing an outdated terrace door with a modern glass front fundamentally changes the appearance of a house. It becomes more open, modern, and brighter. At the same time, such a project is more complex in existing buildings than in new construction, as existing structures must be taken into account. The following points should be clarified before planning begins:

Statics and wall opening

Any widening of an existing wall opening constitutes an intervention in the building's structural integrity. A structural engineer must assess whether the load-bearing wall can support a larger lintel and what underpinning measures are necessary during construction. This is particularly important for masonry buildings constructed between the 1950s and 1980s, where wall thicknesses and material properties can vary considerably.

Since all SUNFLEX systems are developed and manufactured in Germany, SUNFLEX provides complete technical documentation with precise material properties and load limits. Your structural engineer won't receive any surprises from the Far East, but rather reliable manufacturer specifications as the basis for precise and safe calculations.

Check floor structure

Anyone planning a barrier-free design with a recessed floor track must first check whether the existing floor structure is deep enough. The required installation depth depends on the chosen system and the existing floor structure. Your SUNFLEX specialist partner will measure the floor structure on site and determine the exact installation depth for your project.

Wall flatness and tolerance compensation

The wall into which the system is installed must be sufficiently straight. SUNFLEX systems offer varying degrees of tolerance compensation depending on the model: The SF25 and SF35 sliding-folding systems compensate for up to 5 mm, and the SF30 for up to 10 mm. The sliding window systems compensate for up to 12 mm with the SF40 and up to 7 mm with the SF60 and SF80. For more significant unevenness, spacers or a compensating structure are necessary, which your specialist partner will assess during the initial measurements.

Neighborhood

A large glass front as access to a terrace not only changes your own home, but potentially also the view to your neighbors. Anyone planning to create an opening directly adjacent to their neighbor's property should check early on whether the new glazing will allow views into neighboring gardens or living spaces, and vice versa. A brief conversation is often all it takes.

Passive house and low-energy house: The insulated terrace door

Anyone building a passive house or low-energy house places high demands on every building element. A large glass terrace access is one of the most critical points in the energy balance.

For this application, we recommend the SUNFLEX SF80 sliding window system or the SF75 folding sliding door. Both are highly thermally insulated systems. The SF80 achieves U-values ​​starting at 0.75 W/m²K, depending on the size and glazing. The SF80 accommodates glass thicknesses from 52 to 54 mm and has a frame depth of 210 to 320 mm, depending on the track configuration. The frame profile is thermally broken, preventing heat loss and thus contributing to a higher energy efficiency rating for your home. For the SF75, the specific U-value is calculated by your specialist partner on a project-specific basis, depending on the glass selection and element size.

Besides the choice of system, there are other planning points that are particularly relevant for passive houses:

Alignment

Orient large glass fronts to the south to utilize solar heat gains in winter. On north, east, and west sides, glass surfaces should be minimized or well protected.

Shading

Plan for external blinds, awnings, or Venetian blinds from the outset. Large glass surfaces heat up rooms considerably in summer.

Connection and airtightness

The glazing must be integrated into the wall's insulation layer in a thermally insulated and airtight manner, eliminating thermal bridges. Thermally optimized edge seals, so-called warm edges, are standard practice.

Ventilation

A controlled residential ventilation system with heat recovery should be tailored to the solar loads of the glass facade to ensure a stable indoor climate.

Your SUNFLEX specialist partner will perform the specific Uw-value calculation based on your planning documents and will match the choice of glass to the energy requirements of your building.

Terrace door in an exposed location: wind, rain and driving rain

Anyone living on a hillside facing northwest, building near the coast, or with a terrace high above the rooftops needs high-quality terrace glazing that can withstand these conditions. For SUNFLEX systems, wind, driving rain, and gusts that push other terrace doors to their limits are no problem.

Comparison of resistance to driving rain and wind load

For exposed locations, two values ​​are crucial: the resistance to driving rain (tested according to EN 12208) and the wind load class (tested according to EN 12210).

The SUNFLEX SF80 sliding window system achieves the highest tested classes in the SUNFLEX range: driving rain resistance class E750 and wind load class C5. The SF60 also performs very well with driving rain resistance class 9A and wind load class C3/B5. Both systems additionally feature three sealing levels in the labyrinth area, which prevent wind and water from penetrating, even in heavy driving rain.

Your SUNFLEX specialist partner knows the wind load zone of your location and makes the system selection based on the actual requirements on site as well as your individual requirements.

Seniors and people with limited mobility: Easy-to-use terrace doors

Accessibility and ease of use are requirements that become particularly relevant in old age or with physical limitations. Someone who needs a walker to get onto the terrace shouldn't have to lift it over a threshold. And someone who has lost strength in their hands will appreciate a terrace door that opens and closes smoothly.

Barrier-free threshold without tripping hazard

The SUNFLEX sliding window systems SF40, SF60 and SF80, as well as the folding sliding systems SF45, SF55 and SF75, are particularly suitable for these requirements. With both system families, the floor track can be recessed so that the threshold is flush with the floor – barrier-free, without a tripping hazard and without obstacles for walkers, wheelchairs or walking sticks.

Easy operation with little gripping force

The ball-bearing stainless steel rollers of the sliding window systems ensure that even heavy glass panels can be moved with a gentle push. The integrated drive mechanism guarantees that a single movement is all it takes to move several panels simultaneously. This means that terrace access can still be easily opened even when strength diminishes.

Those who incorporate these requirements into the planning early on create a terrace access that is not only comfortable today, but also enables beautiful terrace moments in the future.

Terrace access with a dog: When everyday life demands a lot

Anyone who owns a dog knows the problem: paws on the window, constant in and out, and sometimes even scratching at the door when things get interesting outside. That's why it's important that a terrace door is particularly practical for everyday use by dog ​​owners.

Easy operation even with frequent in and outings daily

Above all, smooth operation is crucial. SUNFLEX systems run on ball-bearing stainless steel rollers and stainless steel tracks. This means that even heavy glass panels can be opened and closed with minimal effort. Anyone who lets their dog out several times a day will quickly appreciate this.

Aluminum frame: Scratches without consequences

All SUNFLEX systems are aluminum constructions with a coated surface. In a household with dogs, this is a practical advantage over wooden frames: wood is softer and therefore more prone to scratches than aluminum. Moisture is another factor. With a wooden frame door, moisture can penetrate the wood through damaged areas of the paint, requiring treatment to prevent swelling. A scratch on an aluminum frame, however, remains purely cosmetic. Nose prints and dirt can also be easily wiped away without damaging the surface.

A terrace door that is opened several times a day and subjected to paw contact must above all be robust and easy to operate. Both of these qualities are inherent in the design of SUNFLEX systems and do not depend on accessories.

There is no single answer to the question of which system is right. The choice depends on what you expect from your terrace glazing, your floor plan, and the specific requirements of your building. The following overview provides guidance.

You want to fully open the entire front

For those who want to completely eliminate the transition between living space and terrace, a system is needed that moves the glass panels entirely out of the opening. SUNFLEX folding-sliding systems achieve this: the panels fold to the side like an accordion, opening up the entire width. Available in insulated versions ranging from uninsulated (SF45) to thermally insulated (SF55/SF55e) to highly thermally insulated (SF75), and also suitable for passive houses.

Prerequisite: Sufficient space must be available to the side of the opening to store the folded panels as a narrow package. Anyone with wall decorations, a pillar, or permanently installed furniture in that area should discuss this with a specialist partner in advance.

They want maximum transparency and a virtually frameless look

For those who refuse to compromise on aesthetics, the SUNFLEX sliding window systems SF40, SF60, and SF80 offer the narrowest profiles in the SUNFLEX range: a mere 21 mm sightline and up to 98% glass area. The sashes glide linearly on tracks, remaining flush with the surface at all times; no element protrudes into the room. This system is the ideal choice for projects with high thermal insulation requirements or burglar resistance up to RC2.

They glaze the outer front of a summer garden or unheated conservatory

Not every terrace enclosure needs to replace a house wall. Those planning a conservatory or sunroom between their living space and outdoor area typically separate the heated living space from the glass area with an insulated wall. The exterior glazing facing the terrace then primarily serves as weather protection. It needs to keep out wind and rain, but not insulate against heat. In this case, uninsulated systems are the right and more economical choice.

For large widths and numerous panels, the SUNFLEX sliding systems SF20, SF22, or SF42 are ideal. The SF20 and SF22 systems achieve widths of up to 19.2 meters and up to twelve panels, while the SF42 reaches up to 18 meters and six panels. The SF42 is unique in the family, offering three sealing levels in the labyrinth seal area, making it suitable for exposed locations. However, unlike the SF20 and SF22, the SF42 cannot be implemented as a barrier-free system due to its design.

For those with a corner layout or who wish to open the entire facade, the SUNFLEX sliding-folding systems SF25, SF30, or SF35 offer the perfect solution. The glass panels rotate outwards and slide to the side, requiring minimal lateral space and allowing the entire facade to be opened up.

They are still undecided

If you're unsure which system is right for your project, the SUNFLEX configurator is a great place to start. Simply enter the width, height, and requirements, and you'll receive an initial overview. A SUNFLEX specialist partner near you will then handle the next steps: taking measurements, detailed planning, and preparing a quote. For any further questions, you can contact SUNFLEX directly using the contact form.

SUNFLEX is a German manufacturer of terrace doors, glass sliding walls, and terrace roofs, headquartered in Wenden in the Sauerland region. The company has been developing, producing, and distributing high-quality sliding, folding, and glazing systems since 1986, though the roots of this family business date back to 1963. Anyone installing a SUNFLEX terrace door today is choosing a system that has been continuously refined for over four decades.

Development and production in Germany

Design, production, and sales are all handled by a single source. This has two tangible benefits that you'll notice in your project: Your structural engineer receives complete technical documentation with precise material properties and load limits, and special requests aren't thwarted by a supplier who only provides standard dimensions. Every system is custom-made.

Tested quality instead of promises

The air permeability, watertightness against driving rain, and wind load resistance of SUNFLEX systems are tested according to European standards. The SF80 sliding window system achieves watertightness against driving rain class E750 and wind load class C5, the highest tested classes in the SUNFLEX range. For burglary protection, versions up to resistance class RC2 according to DIN EN 1627 are available. These values ​​can be found in test reports, which your specialist partner will provide upon request.

Operating worldwide, providing on-site consultation

SUNFLEX systems are deployed across Europe, Africa, the Middle East, North America, Asia, and Latin America, from private terraces to hotel projects, through locations and partners. You'll still receive on-site consultation: a SUNFLEX specialist partner near you will handle the measurements, planning, and quotation. Create your desired configuration directly in the SUNFLEX configurator now, or let our references convince you.