Re-roofing a villa or bungalowGet the details right and it still looks original.

What's usually up there?

Auckland's special character statements describe villa roofs as gabled and hipped, most commonly in corrugated iron, with brick chimneys a feature of many rooflines. Californian bungalows tend to have shallow gable roofs and wide eaves with exposed rafters. After a century of add-ons, expect more than one material, especially on lean-tos.

Matching what the street sees

Start with the profile. Standard corrugate is the usual match, and Roofing Industries makes True Oak, a deeper, rounder corrugate it describes as a return to the original. Curved verandah roofs can be rolled to suit: Metalcraft, for one, offers bullnose, drape and spring curving.

Then the spouting, the detail people forget. Roofing Industries makes an Old Gothic profile it likens to colonial spouting, and Metalcraft a Colonial Quad. Before strip-off, have the barges, ridge and finials photographed so the new ones copy the old shapes.

Shallow bungalow roofs and verandahs

Low pitches are where these re-roofs come unstuck. Roofing Industries puts standard corrugate at a minimum of 8 degrees under E2/AS1, or 10 with end-lapped sheets, and NZMRM's installation guide says corrugate can't finish at the spouting below 8 degrees. Flatter planes may need a deeper corrugate or a rib profile, so ask for every plane to be measured, verandah included.

Old metals that don't mix with new steel

If the chimney or vents are flashed in lead, or there's copper on the house, raise it early. NZ Steel says neither is compatible with ZINCALUME or COLORSTEEL, especially where water runs off onto the coated steel, so new flashings should be soft zinc, aluminium or matching coated steel.

Unpainted iron suits some villas, but NZ Steel doesn't recommend ZINCALUME in its Severe, Very Severe or Extremely Severe categories near the coast, where its range points to COLORSTEEL. And deep verandahs need washing: the Code of Practice says overhangs and soffits that rain rarely reaches collect salt and corrode faster.

Character rules, heritage and consent

In Auckland's Special Character Areas, restoration and repair is permitted but external alterations need resource consent, and Plan Change 120 may change that. The Historic Heritage Overlay asks for the same or closest materials, with no water-blasting or scaffolding fixed to the building. Wellington, Christchurch and Hamilton have their own character rules.

For building consent, iron for iron on the same purlins is the easy case: New Plymouth District Council gives same-type roofing on a roof over 15 years old as typical consent-free work. New purlins, a heavier roof or an early failure can change that, so ask your council.

Decide about the chimney now

With the scaffold up, a re-roof is the natural time. The Natural Hazards Commission says homes built before 1970 most likely have unreinforced chimneys, and its safest option is removal down to floor level, or a light metal flue above the roof if you still use the fire. Removal may need consent. See chimney removal.