Roofing in the Philippines

The Philippines is an archipelago of more than 7,000 islands with a hot, wet tropical climate. Its roofing history runs from steep thatched roofs on raised timber and bamboo houses, through the tile and stone houses of the Spanish colonial era, to a present in which galvanised iron and aluminium sheet covers the great majority of homes.

Because the country sits in a typhoon belt and on an active seismic zone, the main concerns for any Philippine roof are rapid shedding of heavy rain, resistance to wind uplift, light weight in earthquakes and, near the sea, corrosion from salt air.

Climate and hazards

Roofs must cope with intense monsoon rain, high humidity and heat, typhoon winds, earthquakes and, locally, volcanic ashfall. Coastal installations face salt spray. These pressures explain the persistence of steep pitches, deep eaves and light roof structures in both traditional and modern building.

Wind uplift is the critical roof hazard. Typhoon Haiyan (Yolanda) in 2013 badly damaged heritage buildings across 14 provinces of the Visayas. Engineering studies of such buildings identify non-engineered roofs as the most vulnerable part of the envelope, and timber-framed roofs clad in galvanised iron sheet as highly susceptible. Two failure modes dominate: pullout, where uplift pulls screws or nails out of the purlins or rafters, and pullover, where the sheet tears around a fastener that stays in place. Post-event surveys link most economic loss in high winds to breaches of the building envelope.

Roofing history

The oldest surviving evidence of building in the country is landscape rather than architecture: according to UNESCO, the terracing technique used in the Ifugao rice terraces of northern Luzon has been practised for about 2,000 years, and these terraces are associated with villages of thatched houses and granaries.

Before Spanish colonisation, lowland houses (the forerunners of the bahay kubo) were roofed with nipa palm leaves or cogon grass. During the Spanish colonial period (1565-1898), a new urban house type emerged, the bahay na bato ("stone house"), with a masonry lower storey and a timber upper storey. Spanish plans for all-stone mansions were set back by a major Manila earthquake in 1645, and the twin dangers of fire and earthquake pushed builders to keep the light upper floor and other features of the native house.

Bahay na bato roofs were high-pitched, usually hipped, gabled, or a combination. Coverings included curved Spanish clay tiles (teja de curva), nipa, sago palm or cogon thatch, and, from the later 19th century, galvanised iron sheet. By the 2020 census, metal sheet had become the roof of the great majority of Philippine homes.

Traditional and vernacular roofs

• Bahay kubo (nipa hut). A lowland house raised on posts, with a tall, steep thatched roof of nipa, cogon or anahaw leaves. A variant covering, kalaka, uses halved bamboo culms laid alternately face up and face down like clay tiles.
• Ifugao bale. In the Cordillera, the Ifugao house stands on posts almost 2 m (6.5 ft) high and carries a thatched roof shaped like a pyramid, with a smoke outlet at its top. Each post has a thickened ledge near the top to stop rats climbing into the house. The living floor is small, usually 5-8 m2 (54-86 sq ft).
• Bahay na bato. The colonial stone-and-timber house with a hipped (cuatro aguas) or gabled (dos aguas) roof. Hip roofs were favoured because they resist wind better and overhang all sides, shading walls and windows. Small shed roofs over windows are called media agua.

Roofing today

The 2020 Census of Population and Housing counted 28.50 million housing units, up from 21.29 million in 2010. Of occupied housing units in 2020, 85.9% had roofs of galvanised iron or aluminium, 4.7% had cogon, nipa or anahaw thatch, and 4.5% had concrete or clay tile. Outer walls were concrete, brick or stone in 60.4% of units, showing that a masonry house under a metal-sheet roof is now the typical Philippine dwelling.

Corrugated and long-span profiled steel sheet, usually zinc- or zinc-aluminium-coated and often pre-painted, is used on houses, churches, schools, factories and warehouses. Reinforced concrete flat roofs are common on urban multi-storey buildings. Thatch survives mainly on rural houses, resort buildings and heritage structures.

Codes, standards and regulation

The National Building Code of the Philippines is Presidential Decree No. 1096, which took effect on 19 February 1977 and replaced Republic Act No. 6541 of 1972. It covers the design, construction, alteration, repair, use and demolition of public and private buildings, but traditional indigenous family dwellings are excluded from its general application. Revised Implementing Rules and Regulations were issued by the Department of Public Works and Highways (DPWH) in October 2004 and took effect on 1 May 2005.

Section 301 of the code requires a building permit before a building is erected, altered, repaired or demolished. The DPWH Secretary administers the code, supported by the National Building Code Development Office, while local building officials issue permits and inspect work. Structural matters, including wind and earthquake loads on roofs, are handled through referral codes that the DPWH adopts, principally the National Structural Code of the Philippines (NSCP). Its 2015 edition bases wind-load calculations on the American standard ASCE 7-10. Design wind speeds vary by location and building risk category; for Category III structures, published examples include 250 km/h (about 155 mph) for Manila, 260 km/h (162 mph) for Cebu and 270 km/h (168 mph) for Bohol.

Industry

The roofing market is dominated by steel sheet, roll-formed locally from coated coil, alongside clay and concrete tile and fibre-cement products.

Notable roofs

• Rice Terraces of the Philippine Cordilleras (UNESCO World Heritage): the Mayoyao cluster has terraces interspersed with traditional farmhouses (bale) and granaries (alang). The site was placed on the List of World Heritage in Danger in 2001 and removed from it in 2012.
• Surviving bahay na bato in historic towns show tiled, galvanised iron and occasionally thatched roofs side by side.

Local roofing terms

• bale - Ifugao house; abong - hut; alang - granary (Ifugao)
• cuatro aguas - hip roof; dos aguas - gable roof (Spanish colonial)
• media agua - small shed roof over a window
• teja de curva - curved Spanish clay tile
• kalaka - halved bamboo used as roof "tiles"
• nipa, cogon, anahaw - palm leaf and grass thatch materials

Sources and gaps

National roofing trade association data, information on national roofing manufacturers and the full NSCP wind-zone map: published information is limited.