Types of roof and the Catalan roof

Knowing what kind of roof a building has is the first step to maintaining or repairing it properly: each type is built differently, ages differently and needs different waterproofing. In this guide we go through the most common types and take a closer look at the most characteristic one in Barcelona and Catalonia, the Catalan roof.

The Catalan roof

The Catalan roof (in Spanish, cubierta a la catalana; in Catalan, coberta a la catalana) is a ventilated flat roof that became popular in Catalonia in the late 19th century and for much of the 20th. It is found on a huge number of roof terraces in the Eixample, in Gràcia and in the old town centres of the Vallès.

How it is built

1. The slab, which is the ceiling of the top floor.
2. The dwarf walls (tabiquillos palomeros): small brick walls built on the slab, which create the fall.
3. A deck of rasillas (thin bricks), normally in two layers, resting on the dwarf walls.
4. The ceramic floor tiles, which are what you walk on.

Between the slab and the deck there is an air gap ventilated through openings in the parapets. That ventilation is the key to the system: it carries away heat in summer and keeps the slab dry, separated from the weather.

Common problems

• Cracks in the deck and floor tiles due to expansion, especially where there are no movement joints.
• Broken or loose rasillas and tiles, letting water into the air gap.
• Missing or ageing waterproofing: many were built with no membrane or have been patch-repaired.
• Vents blocked during earlier alterations, causing damp to build up in the air gap.
• Deteriorated dwarf walls that no longer support the deck properly.

How it is refurbished

The first step is to inspect it, ideally by opening up a small test area to see the condition of the air gap and the dwarf walls. From there, there are two routes:

• If the deck and floor tiles are sound, the cracks are repaired, movement joints are formed and a continuous waterproofing system such as hot-spray polyurea is applied over the top, without taking up the roof terrace.
• If the deck is broken or the slab is damp, it is taken up, the dwarf walls are repaired, the deck is rebuilt, a waterproofing membrane is laid and the roof is retiled. This is also the time to add thermal insulation.

In both cases the ventilation of the air gap must be preserved: blocking it is one of the most frequent mistakes when altering a Catalan roof.

Flat roofs

They have a very slight fall, just enough to carry water to the outlets. They are classified by use and construction:

• Accessible: terraces and roof terraces that are used. They have a floor finish over the waterproofing.
• Non-accessible: only walked on for maintenance. They are finished with gravel, a mineral-surfaced membrane or a continuous coating.
• Conventional: the insulation goes under the waterproofing.
• Inverted: the insulation goes on top of the waterproofing and protects it from the sun and temperature changes.
• Ventilated: with an air gap, like the Catalan roof.

Their weak points are the joints, the outlets, the junctions with parapets and walls and anywhere water is left standing.

Pitched roofs

They shed water through their own slope. The most common are:

• Tiled (curved clay, interlocking or plain tiles), on traditional homes and buildings. They need an underlay beneath the tiles and checks for broken or slipped tiles.
• Metal sheet or sandwich panel, typical of industrial buildings. Their critical points are the laps, the fixings, the rooflights and the gutters.
• Fibre cement, on older buildings. They usually contain asbestos and can only be removed by companies listed on the official register (RERA).

Green roofs

They have vegetation growing on the roof. They improve insulation and help manage rainwater, but they require waterproofing with root protection and a good drainage system, because the roof is damp much of the time.

Which waterproofing each type needs

Type of roof	Usual systems
Catalan roof	Polyurea or other continuous systems over the floor tiles; or a membrane under new tiles if it is rebuilt.
Accessible flat roof	Double bitumen membrane under tiles, polyurea or liquid membranes.
Non-accessible flat roof	Mineral-surfaced membranes, PVC or EPDM, liquid systems or polyurea.
Pitched tiled roof	Underlay beneath the tiles and checks of tiles and flashings.
Industrial (metal sheet or panel)	Continuous membranes or sprayed polyurea, with particular attention to laps and flashings.
Green roof	Membrane with root protection, plus drainage and filter layers.

If you are not sure what kind of roof your building has or what it needs, we will inspect it with no obligation. Find out more in roof waterproofing and roof refurbishment.

Frequently asked questions