Glass curtains by the sea:wind, salt and maintenance

Yes, glass curtains work on the seafront, but the sea asks more of them. Spain's building code gives the shoreline a wind exposure factor almost double the town figure at low heights, and salt attacks tracks and fixings. Ask for a coastal grade coating, A4 stainless screws and a fresh water rinse every few months.

Being on the coast does not rule them out, but it changes two things: how hard the wind pushes and how quickly the metal parts get dirty and corrode. An enclosure that needs almost no attention in an inland courtyard will want more frequent checks, and materials chosen with salt in mind, on a balcony facing the beach or a penthouse above the promenade. That applies right across our working area from Valencia to Murcia.

By the sea the small parts wear first: rollers, bearings, seals and screws. Toughened glass and well protected aluminium cope with salty air for years, but salt mixed with sand turns the bottom track into fine sandpaper. That is why seaside care is mostly about the tracks and rinsing with fresh water, rather than about the glass itself. Which materials and finishes LUNEKS uses on seafront jobs

The SE-AE section of the Spanish building code sets the basic dynamic wind pressure at 0.42, 0.45 and 0.52 kN/m² for zones A, B and C of the national map. Alicante sits in zone B, according to the Normatia technical sheet for Alicante. That pressure is then multiplied by an exposure factor that depends on height and surroundings, and the harshest surroundings in the whole table are the seashore.

Table 3.4 of the same document gives a seashore with at least five kilometres of open water in front of it a factor of 2.7 at six metres up, against 1.4 in a built-up urban area. At 15 metres, roughly a fifth floor, the figures are 3.3 against 2.1. Put simply, the same panel facing the beach takes between 42 and 93 % more pressure than one further into town, and the system has to be sized for that.

First and foremost, the system should be designed for the real wind on that particular façade, not an average figure. Glass thickness, the spacing of the fixings and the type of track all depend on height and on how exposed the terrace is. Glass curtains for a ground floor flat with a garden and for a penthouse 20 metres above the promenade should not share the same specification.

In a strong easterly or a storm, the panels should be fully closed and locked, or completely stacked away. A panel left half open acts like a sail and strains the hinges and the track. Ask the fitter to show you the lock on day one, and use it whenever you leave home with wind in the forecast. What wind speeds LUNEKS systems are tested to and which glass thicknesses the company fits

• A wind load calculation for the height and orientation of the façade
• Toughened glass of the thickness that calculation calls for
• An aluminium coating rated for marine conditions
• Screws and anchors in A4 (AISI 316) stainless steel
• A bottom track with drainage, so salt does not settle in the channel

Sea air carries chlorides that settle on the profiles and, together with overnight damp, attack any unprotected spot in the metal: cut ends, drill holes, scratches in the coating. That is why the Qualicoat association created its Seaside class for projects within five kilometres of the coast, which requires etching away at least 2 g/m² of aluminium before coating instead of 1, as Glass Times reports on the Seaside class.

For fixings, molybdenum makes the difference. Type 316 stainless steel, marked A4 on screws, resists localised chloride attack better than type 304 or A2, as the Wikipedia article on 316L stainless steel notes. On the seafront a lower grade screw eventually shows rust spots, and the brown streaks stain both the coating and the glass. If you would like the aluminium in another colour, our RAL coating page sets out the options.

More often than inland. The aluminium systems maker Reynaers recommends using its care product on profiles and glass twice a year in rural settings and four times a year in aggressive environments such as the coast, as Interempresas reported when its care manual came out. As a working rule on the seafront, rinse the curtains with fresh water every three months and again after every storm.

The weak spot is the bottom track. Sand, salt and rainwater collect there, and that mixture wears down rollers and brush seals until the panels start to drag. Vacuuming the track before you wet it stops the sand acting like sandpaper. Worn parts can be replaced without taking the glass out, as we explain on our seals and spare parts page.

Glass curtain seals are usually made of EPDM rubber or similar elastomers. EPDM is known for its resistance to heat, ozone and weathering, and when properly formulated it can be used outdoors for years or even decades without breaking down, as the Wikipedia article on EPDM rubber explains. That matters in a city that, according to AEMET, gets around 2,851 hours of sunshine a year. Seal material used in LUNEKS systems

What shortens their life on the beach is not the sun but friction. Sand stuck to the rubber by the salt acts as an abrasive every time the panel slides, and the seal loses its shape early. Wiping the seals with a damp cloth when you rinse the track, and never forcing a panel that drags, stretches the time between replacements considerably.