Roofing Material Options

When it comes to adding the crowning glory to your new house or replacing a tired cap on your treasured home, there are some critical roofing decisions to be made that include performance and cost.*

a purple roofing
ARTICLE Jason Burgess

When it comes to adding the crowning glory to your new house or replacing a tired cap on your treasured home, there are some critical roofing decisions to be made that include performance and cost.*
Geographical location, environmental conditions and good design are key factors when considering roofing options, as are durability, longevity, maintenance and the pitch of your roof. Getting all the elements right the first time could save you thousands down the line.
There are many factors to consider when pricing a roofing project. Each home is different and variations on costs can occur for many reasons including site access, elevation, scaffold hireage, unusual roof shapes.
It should be noted that for all roofing jobs a scaffold or edge protection is mandatory. This can add a significant cost to the project so make sure this cost is factored in upfront. Virtually all roofing-work now requires licensed trade professionals to carry out the installation.
If you are changing a roofline or an existing roofing product on your home you must apply for a building consent. Conversely no building consent is necessary if a  'like-for-like'  roof cladding is being installed, or for repair work or normal re-roofing where a roof is more than 15 years old.

Metal

from $55 per square metre
The traditional galvanized corrugated iron has largely been superceded by zinc/aluminium alloy-coated mild steel. It’s lightweight, easy to install, and comes in a wide range of colours and profiles. With Coloursteel starting from around $55 plus GST per square metre, it’s the most cost-effective roofing option with a  ‘standard’  three-bedroom house priced around $10,000 to $12,000 to roof or re-roof.
While each design profile will have specified minimum slopes some metal roofs can be laid on as little as a 3 degree pitch. As a simple rule of thumb: if you can see the sea from your house it’s best to use an aluminium substrate. Avoid using copper/brass and stainless fixtures with galvanised steel, zinc/aluminium coated steel or pre-painted steel as water travelling from copper or brass can hasten corrosion.
Metal roofing materials also come as pressed tiles, from around $55 per square metre. They’re typically made from G300 grade zinc/aluminium alloy-coated mild steel, formed into individual shingles or tiles, or into modular panels that mimic a row of shingles or tiles, with a natural stone chip protective coating or a pre-painted finish. They are suitable for roof pitches over 10 degrees.

Membrane

from $80 per square metre
Butyl rubber membranes are suitable only for  ‘flat roofs’  (between one and 10 degrees). Membranes can also be used on curved roofs. They are lightweight, tensile, easy to repair and resistant to UV rays, ozone and weathering. Some products are 100 per cent recyclable thus environmentally friendly. Butyl or the wider EPDM rubber is fitted in two sheets over a plywood or concrete substrate. They can be lap joined by rolling or  ‘welded’  using hot air. Prices for butyl start at around $80 per square metre.
Torched-on bitumen products have elastic polymers and a fiberglass component for extra strength, are thicker and are joined with a naked flame leaving a seamless finish. These membrane sheets range from 2.1 to 6 metres in width, with prices starting from $105 per square metre. Larger sheets reduce the amount of seams and the labour cost.

Concrete and clay

from $65 per square metre
Concrete and terracotta clay tiles are extremely durable, require less maintenance than most other roofing products and are conducive to all environments and steep pitched roofs over 10 degrees. A wide range of tile colours and profiles is available. Concrete tiles cost from approximately $65 per square metre. Quality French clay tiles start from around $180 to $240 per square metre with lead flashings. 
Concrete and clay do not rust, warp or corrode. They are impervious to frost and ice and can handle high winds. Another plus is that they are up to 30 decibels quieter than iron, which is handy in high density housing situations. The downside is that they are 30 per cent heavier than iron/metal, so extra truss costs should be factored in. Concrete tiles are not suitable for curving roofs and walking directly on the tile is not recommended.
The thermal mass of concrete roofs will effectively reduce heat loss. The laps in a concrete tile roof allow the roof space to breathe so moisture can escape. They are naturally inert therefore any drinking water collected from them will not contain zinc or aluminium ions.

Slate

from $250 per square metre
Slate tiles are hewn from actual stone. They have been used for centuries all over the world and as such have stood the test of time in saltwater locations and extreme temperatures. Slate roofing meets building code requirement in all corrosions zones. It provides good fire protection, is low maintenance, resistant to rot and insects and can last up to 400 years.
Available in different sizes and colours, slate tiles cost from around $250 for entry-level Spanish slate and from $300 for higher-grade Welsh slate. Slate is very heavy and requires expensive extra support. It’s suitable for roofs with a minimum pitch of 25 degrees.
A lighter weight and cheaper alternative (from around $190 per square metre) to slate is synthetic slate. It’s made from 80 per cent post-industrial recycled rubber and plastics. Synthetic slate tiles are at least as strong and possibly more durable than traditional slate tiles. They meet the Class C fire resistance code and can sustain winds up to 160 kilometres per hour. They require a plywood substrate and are suitable for steeper pitches.

Copper

from $260 per square metre

Like terracotta and slate, copper has an architectural legacy dating back hundreds of years. Properly installed copper meets the full building lifetime durability required by the Building Act. It’s very strong and can withstand temperature extremes from minus 196 to 600 degrees Celsius. It will not melt, burn or give off toxic fumes in a house fire.
Copper, like zinc, aluminium and stainless steel, can be laid on roofs with pitches from 3 to 10 degrees depending on the profile, length and local conditions. As one of nature’s trace elements it’s 100 per cent recyclable and impermeable to contaminants from the external environment. Copper is also a natural inhibitor to bacterial growth and is essential to health and diet, so makes an ideal surface for tank water collection. The only downside is cost, starting from around $260 per square metre for a tray style roof.

Ashpalt

from $65 per square metre
Asphalt shingles are one of the fastest growing roofing choices on the market, available from around $65 per square metre. They are made from fibreglass-reinforced asphalt with non-combustible fibres and a ceramic-coated metal or stone chip surface. Resistant to corrosion and rot, they can weather harsh conditions and are generally low maintenance. Some heavier weight shingles boast warranties of 25 plus years.
A 15 to 18 degree pitch is recommended as a minimum, but with special installation procedures they can be laid to pitches as low as 10 degrees. They are installed over a plywood substrate (with stainless nails and a bitumen based adhesive/sealant) and can be physically bent into shape to provide workable solutions for complex roof profiles. During installation temperatures need to be at least 10 degrees Celsius or they can become brittle and crack.

Timber

from $160 per square metre
Timber shakes and shingles are similar products cut from treated or naturally durable timbers. Shingles are tapered with relatively smooth front and back faces; shakes have a more textured, rustic surface than shingles. While most timber shakes and shingles are imported western red cedar, you can also get locally produced first grade ACQ-treated radiata pine products. Both provide low maintenance durability with low thermal and moisture movement properties.
Timber shakes and shingles may have a limited lifespan of between 7 and 10 years in damp conditions, but will last much longer in a drier climate. They can be laid on 18 degree or steeper pitches (25 to 30 degree pitches are best for effective water dispersion). Shingles are slightly cheaper than shakes, starting from around $160 per square metre as compared to $195 for first grade cedar products.

Note: Prices are rough approximations only, and Refresh Renovations cannot be held accountable for their accuracy, All prices in this article are exclusive of installation costs and any variations.

You might be interested in reading: Roofing colour options.

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This article by Jason Burgessfeatured in Issue 006 of Renovate Magazine. Renovate Magazine is an easy to use resource providing fresh inspiration and motivation at every turn of the page.

 

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*All information is believed to be true at time of publishing and is subject to change.

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