Roof cladding: original details

Original roof cladding was generally corrugated steel, asbestos-cement shingle, or Marseille tile.

Corrugated galvanised steel roofing

The most common roof cladding featured on bungalows, particularly where the roof pitch was very low, was corrugated galvanised steel. It was available in short lengths or runs that were typically 8’ (2.4 m) long and 2’1½” (648 mm) wide.

The sheet steel used in New Zealand was nominally 26 (Birmingham) gauge – with a thickness of 0.018” (0.45 mm) – but it tended to be about 20% thinner than British standard.

Sheets were often laid as over and under sheets, and not continuously lapped as today.

Sheets were generally laid with a one-and-a-half lap cover, and two laps in exposed situations. The exposed edge of the sheet should be facing away from the prevailing wind. 

Fixings

Sheets were fixed with 2½ ” or 3” (63 or 76 mm) long, lead-head, galvanised nails fixed through the tops of the corrugations.

Flashings

Lead-edged galvanised iron ridge and hip flashings enabled the flashing to be dressed to the corrugated profile. Flashings to complex junctions such as the hip/ridge junction and around pipe and chimney penetrations were generally in lead.

Valleys and the details around dormers were formed with folded, flat sheet, galvanised steel flashings. 

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Asbestos-cement shingles

Asbestos-cement shingles or slates became popular for roofing in the early 20th century because they were economical and considered to be inflammable. 

They were made from a combination of asbestos fibres and Portland cement that were mixed together and pressed in a variety of patterns to form shingles that were between 1/8–½” (3–6 mm) thick. 

Coloured pigments were sometimes added to the wet mix before pressing, or were rolled onto the surface of the shingles after pressing. Unfortunately, the early coloured shingles faded quite rapidly. 

Shingles were laid in a similar way to slate roofing, and they were easily punched, filed and trimmed to size on site. They could be laid in a conventional shingle/slate pattern or diagonally in a diamond pattern (Figure 1) and were often finished with Marseille ridge tiles.

 

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Tiles 

Bungalow roofs where the pitch was around 25–30° sometimes had a Marseille tile roof (Figure 2). 

These were doubled-pressed, terracotta-coloured interlocking clay tiles. They were introduced into New Zealand in the late 19th century and promoted here in the early 20th century, but were soon being manufactured in New Zealand at the O’Reilly Brothers factory in Taumaranui. 

A half share of the factory was purchased by Winstone Ltd in 1913, who then purchased the remainder of the factory in 1920. Winstone Ltd continued to manufacture bricks and Marseille tiles at the factory until it was closed in 1959.