Metal Roofing: Noise, Corrosion and Colour Choice

How to choose profile, coating and roof build-up so a metal roof stays quiet in the rain, resists rust and keeps its colour for years.

Metal roofing is light, quick to install and long-lasting when chosen well. Yet most complaints about it revolve around the same three issues: drumming indoors when it rains, rust that starts at cut edges, and colour that fades after a few summers. In each case the root cause is usually not the metal itself but decisions made during selection and installation.

Types of metal roofing

The most common options are metal tiles, trapezoidal profiled sheets and standing-seam roofing. Metal tiles imitate the wavy shape of clay tiles and are popular on pitched roofs of private houses. Profiled sheets look plainer and are widely used on outbuildings, garages and industrial buildings. Standing-seam roofs are made of long panels joined by folded seams with hidden fixings; they look cleaner architecturally but demand skilled installers.

Appearance is not the only criterion. The roof pitch must not be lower than the minimum stated by the manufacturer for the chosen profile, otherwise wind can drive rainwater into the laps.

Rain noise: where it comes from and how to reduce it

Thin metal amplifies the impact of raindrops through resonance. How much of that sound reaches the rooms depends on what lies beneath the sheet. In a house with a cold, ventilated loft between ceiling and roof, the noise is largely absorbed. In an attic bedroom, however, only a few layers separate the metal from the ceiling, and noise becomes far more noticeable.

Practical ways to reduce it:

• fill the space under the roof completely with dense fibrous insulation such as mineral wool;
• fix the battens at the right spacing and firmly, so the sheet does not vibrate;
• avoid overtightening or leaving screws loose, as both increase vibration;
• line attic ceilings with heavy materials, for example two layers of plasterboard.

Thicker steel vibrates less, but thickness alone does not solve the problem without insulation.

Corrosion: zinc, polymer coatings and cut edges

The main barrier protecting steel from rust is the zinc layer. On top of it come a primer and a decorative polymer coating such as polyester, matt polyester, Pural or PVDF. The level of protection depends on zinc thickness and polymer type, both of which appear on the certificate and data sheet. It is worth asking the supplier for these documents, because two sheets that look identical can have very different service lives.

Rust most often begins at cut edges and scratches. Sheets should never be cut with an abrasive angle grinder: the heat burns both the zinc and the polymer and leaves spark marks. Use shears or a suitable saw, and touch up any scratches with the manufacturer's repair paint. Near the sea, salty air raises the risk of corrosion, so the coating class must suit that environment.

Colour and fading

Colour is not purely an aesthetic decision. Dark roofs heat up more in the sun, which affects loft and attic temperatures in summer; in a hot climate lighter shades reduce the heat load. Some saturated colours, especially reds and bright greens, can also fade faster under ultraviolet light. The UV resistance of the polymer layer is listed separately in the technical data.

Consider roof colour together with the facade material, window frames and gutters. A real sample checked in daylight next to the facade finish is more reliable than a printed catalogue swatch.

Condensation and fixing

The most hidden problem under a metal roof is condensation. When warm, moist air touches cold metal, droplets form and can soak the insulation. To prevent this, a breathable membrane is laid under the sheets with a ventilated gap between it and the roofing, while a vapour barrier goes on the room side.

Fixing uses roofing screws with rubber washers. Each screw should be driven straight and tightened so the washer is slightly compressed but not crushed. At handover, check that:

• sheet overlaps have the correct length and face the right way relative to the prevailing wind;
• snow guards, gutters and ridge pieces match the design;
• chimney and wall junctions have flashing and sealant;
• cut edges and scratches have been touched up.

Zaferoğlu İnşaat carries out construction work from excavation through to the roof covering. Metal roofing is best chosen while the house is still being designed; our Babək Plaza office can advise.