How much does a large glass leaf weigh?
The sum is simple: each millimetre of glass weighs about 2.5 kg per square metre. A 6+16+6 mm double-glazed unit gives 12 mm of glass, about 30 kg/m2, and a triple 8+12+8+12+8 mm unit about 60 kg/m2. A 3 × 1.5 m leaf (4.5 m2) with double glazing weighs around 135 kg, with triple about 270 kg, plus frame and hardware. Large lift-and-slide leaves in modern systems easily reach 300 to 500 kg or more.
Weight decides everything else: hardware type (lift-and-slide, rollers), strength of the support, installation method and the size of lifting equipment. So leaf sizes are chosen with the manufacturer, not from a designer's sketch. A system that looks good in the render but has a 250 kg limit will not carry your leaf.
What is a slim frame and how is it different?
Minimal sliding systems hide the frame in the wall and floor and leave only the vertical joint between leaves visible, usually from about 20 to 30 mm. The rest is glass, and a view of the sea or the city looks like a picture without a frame. The great advantage: light and views; the great cost: complex installation and precision in the openings.
You pay for the narrow profile: reinforced steel or aluminium cores, thermal break, high-precision hardware. And for tolerances: wall, floor and ceiling must be flat to within millimetres or the leaves jam. So in premium projects the opening is prepared in advance to the manufacturer's template and the frame goes in before final finishes, not after.
Can a flush threshold be done without leaks?
It can, if the threshold is designed as a construction detail. The profile sinks into the floor, the terrace waterproofing passes beneath it, raised above floor level, a linear drainage channel with a hidden grille sits in front of the door, and a small height margin is kept inside. Water that wind drives under the door falls into the channel and not into the flat.
You cannot bury the threshold in the screed, cut the waterproofing at glass level and trust silicone. That solution leaks after a winter. Another factor is wind: in gusts with rain, water hits the profile horizontally, and the tightness of the leaves by test class matters as much as the threshold. For the detail, see the articles on terrace waterproofing and terrace flooring.
How do you get huge glass panes up to the top floor?
Large panes will not pass through staircase and lift; they are usually lifted with a crane or manipulator with special suction cups via the facade or the terrace. You need access, space on the street for a mobile crane and permission to occupy public space (arranged separately in Barcelona), sometimes closing traffic for a few hours. The installation date is coordinated with the town hall and the comunidad.
Plan ahead: pane sizes must pass through the terrace opening and between structures, the leaf weight must fit the machine's capacity and the terrace must carry the machine and people during installation. This is decided at the time of ordering: moving the date and reordering glass costs more than preparing. And consider a spare pane, because a second batch takes weeks.
Do you need permission to replace penthouse windows?
Most likely yes: if the facade appearance, opening size, profile colour and composition change, comunidad consent is needed, and in protected zones of Barcelona the town hall may restrict material and colour. Replacing like for like is simpler than enlarging the glazing and moving to panoramic walls.
The order: statutes and comunidad minutes, an enquiry at the district office, a technical description, then the order. For details on permits for replacing facade windows see the article on changing windows. If you alter the opening (removing a parapet, enlarging the glazing), it is a structural change and a technician's project cannot be skipped.
Shading, views and neighbours' windows
A large glass wall gives light, but also heat and views in both directions. For the hot-sun side choose glass with a solar layer and external shading (awning, blinds, pergola); for the side facing neighbours, satin glass on the lower part or curtains that do not alter the facade. For more on overheating see the article on the hot penthouse.
It is better to check sightlines before ordering: stand on the terrace and look at where the windows opposite face and from where you are seen. A sliding wall combines better with planted screens, partitions and awnings than with a blank wall. And remember evening light: a large pane turns into a mirror if it is bright inside, and the view outwards disappears.
Where to start and how BCN YARD can help
Start with three measurements: opening width and height, the height between slab and finished floor, the terrace load and the route for glass delivery. Then choose the system with the manufacturer and work out the threshold and waterproofing detail.
BCN YARD handles penthouse renovations in Russian and Spanish, with one person responsible for the site. A visit and measurements, then a phased estimate where windows, threshold, waterproofing, crane and approvals run on one schedule and are not a set of separate orders.
Frequently asked questions
Which glazing is best for a panoramic sliding wall?
For a big wall on the coast double or triple glazing with low-emissivity and solar-control coatings is usually chosen, plus laminated safety glass at height. The choice depends on noise, orientation and weight: triple is heavier and costlier, double allows wider leaves. It is decided by calculation, not by catalogue.
How long does the hardware of large sliding leaves last?
Life depends on the system, track cleanliness and servicing. Once a year the rail needs cleaning, the mechanism lubricating and seals checking, especially by the sea, where salt and sand get into the guides. Ask the manufacturer for a service agreement or instructions.
Are insect screens and curtains needed on a glass wall?
They are not mandatory but very practical: integrated insect screens and concealed external blinds give ventilation and sun protection without spoiling the view. They are planned from the start because the connection and the recess in the opening and ceiling are resolved at the finishing stage, not afterwards.