Roofing in the Netherlands

The Netherlands is a flat, low-lying, densely populated country with a mild, wet and windy North Sea climate. Its traditional roofs are of two kinds: ceramic tiles, above all the S-shaped Dutch pantile (Hollandse pan), and water-reed thatch. Post-war housing and city buildings added large numbers of flat roofs, which are now being turned into green, blue and solar roofs.

Climate and hazards

Wind and rain are the main loads on Dutch roofs, and North Sea storms test the fixing of tiles and ridges. Because so much of the country lies low and water management is a national priority, holding back rainwater on roofs has become an important planning aim. Fire is the main regulatory concern for thatch, which is closely controlled in the national building decree.

Roofing history

Thatch was the ordinary roof of the North Sea lowlands for centuries. In towns, fire drove change: in the 16th century Holland required fireproof roofing materials in towns, which encouraged clay tiles and supported many small tile makers. Dutch tiles and slate moved both ways across the North Sea. Under Elizabeth I, quarries at Delabole in Cornwall shipped slate to the Netherlands, while from the early 17th century Dutch pantiles were exported to eastern England and Scotland. Dutch settlers also set up full-scale roof tile production in the upper Hudson valley of North America by 1650.

As tiles took over in towns, thatch became mainly a rural roof, used on farmhouses and barns. In the 20th century it changed status: once the roof of less well-off households, reed thatch is now often chosen for villas and even whole new neighbourhoods.

Traditional and vernacular roofs

• Hollandse pan: a single-lap S-shaped clay pantile, traditionally orange-red, also made in glazed and smoked (blue-grey) finishes.
• Reed thatch (rieten dak): water reed (Phragmites australis) laid in bundles on steep roofs of about 45-55 degrees, either stitched to battens (a gebonden dak) or screwed through to a closed deck (a schroefdak). Ridges are finished with clay ridge tiles, turf or, in modern work, metal or composite caps. One published Dutch detail specifies a reed layer 300 mm (12 in) thick.

Roofing today

Ceramic interlocking and pantile roofs are the norm on pitched-roof houses, with concrete tiles also used. Flat roofs on terraced housing, apartments and commercial buildings use bituminous, EPDM and other synthetic membranes, and Dutch cities increasingly promote green roofs and blue roofs (roofs that store rainwater temporarily). Thatch remains a living trade, but suitable reed is scarce, much of it is imported, and firms report a shortage of skilled thatchers.

Codes, standards and regulation

Building work is governed nationally by the Besluit bouwwerken leefomgeving (Bbl, building decree). Article 4.47 requires the top surface of a roof to be "not fire-dangerous" when tested to the Dutch standard NEN 6063. Exceptions apply to buildings of up to 50 m² (about 540 ft²) of floor area, and to buildings without a raised habitable floor where the fire-dangerous roof parts are at least 15 m (49 ft) from the plot boundary. A thatched house closer than that to the boundary therefore needs an accepted fire-safe solution, such as an external fire-retardant coating (renewed about every five years), a roof sprinkler system, or a screwed thatch on a closed, fire-resistant deck accepted as an equivalent solution. European EN standards apply to roofing products.

Industry

The Vakfederatie Rietdekkers (Dutch thatchers' federation) publishes technical requirements and guidance for reed roofs, including joint guidance on fire-safe thatch details. Large international groups such as BMI (through its Monier brand) supply Dutch tile roofs.

Notable roofs

• House of the Five Senses at the Efteling theme park in Kaatsheuvel, often described as having the largest thatched roof in the world.
• The tiled roofscapes of historic Dutch towns, shaped by the 16th-century fire rules.

Local roofing terms

• Dakpan: roof tile; Hollandse pan: Dutch pantile.
• Riet: reed; rietdekker: thatcher.
• Gebonden dak: stitched (bound) thatch; schroefdak: screwed thatch.
• Nok: ridge.
• Gesmoord: smoked (blue-grey) tile finish; verglaasd: glazed.

Sources and gaps

Housing statistics on roof coverings and counts of thatched buildings: published information is limited.