Residential construction in New Zealand is big business with around 20,000 new homes being built this year.
That number is tipped to increase to 40,000 annually, so it's not surprising that the wood and lightweight steel-framing factions have pitched their tents to fight for every cent.
The timber-framing fraternity claims steel-framed houses are hard to insulate, pose a serious hazard to life if the framing comes into contact with live electrical wires, and emit loads of ozone-depleting carbon dioxide.
These points are countered by the steel-framed set, which says insulation is no problem, installed circuit breakers eliminate the risk of electrocution, and CO 2 emissions are about the same as for timber framing.
Arguments abound on the durability of each respective framing system, on the relative fire safeguards, and on the ease of use in terms of cutting and fixing.
Both camps say their respective products have been tested to withstand extreme seismic activity.
The cost of both framing options is about the same, although there is some argument around that too, but lightweight steel framing weighs less than timber.
The fallout from rotting houses involved in the leaky homes nightmare has been cited as one reason why steel framing is gaining popularity.
But local sawmillers are under pressure, with one folding about a month ago, and others reportedly under the gun.
A Building Research Association of New Zealand (BRANZ) paper, the Physical Characteristics of New Houses 2012, says timber framing is the predominant structural material but its use has been trending down over the past decade, losing more than 10 per cent market share.
National Association of Steel Framed Housing (NASH) covers the light steel framing industry - high strength, cold rolled steel - mainly used for housing, internal partitions and fitouts, and two-three storey buildings.
NASH general manager Carl Davies says market share for steel framing has increased from one per cent in 2008 to between seven and eight per cent today.
"It is not the NASH intention for steel framing to become the dominant type of framing for buildings. We just want the discerning consumer to have choice."
The industry has developed standards, investigated how the product performs under extreme conditions, and developed professional courses for builders and building officials, he says.
New Zealand Timber Industry Federation chief executive Brent Coffey says the industry is "deeply concerned" about the downward trend in the use of timber framing but believes it can be reversed.
"We feel that this trend could be a symptom of the leaky building fiasco. As we now know, the reason these leaky buildings failed was poor design and bad construction techniques that allowed water to become trapped in the wall cavities. What the public saw when the walls were removed was images of rotting timber frames. This was incredibly misleading as it wasn't the timber at blame. Some of the substitution to other framing materials during this 10-year period could be by those that don't realise timber was not at fault in those situations."
Since the onslaught of leaky homes, the industry has enhanced the way it treats and grades timber for strength leading to a far better product, Coffey says.
He adds that the loss of market share in structural timber could harm local sawmillers.
"Any loss of market share is a hard thing to cope with and if this trend were to continue long term then it would certainly be a serious threat to the health of the sawmilling industry."
R EGISTERED Master Builders Federation of New Zealand chief executive Warwick Quinn estimates about 5 per cent of the 20,000 new houses built this year will utilise steel framing. He says that figure looks destined to grow.
"People are getting a lot more comfortable with the concept of steel framing. From what I can see, it is slowly gaining traction."
The fact that steel framing is included in the building code and is accepted by local authorities as an alternative when approving consents has contributed to its rise in popularity, Quinn says.
According to NASH, steel framing has been used in this country for more than 50 years. Across the ditch about 15 per cent of new homes use it.
Quinn believes the housing demand in Auckland, which is tipped to need 400,000 new houses over the next 30 years, and the 10,000 to 20,000 replacement homes still needed in Christchurch, leaves plenty of scope for both timber and steel framing.
B UT a looming battleground is the impact from the importation of steel-framed, kitset houses from China.
The local framing industry - both timber and steel - faces the possibility of losing market share to imported product.
Quinn says Master Builders isn't concerned that cheaper foreign steel-framing may come into the country.
"There is no problem so long as it meets the quality test . . . and you can assure it meets the building code requirements . . .
"We support innovation, competitiveness, anything that makes housing more affordable, attractive and more of an option for construction for homeowners," he says.
NASH's Davies says his organisation "do have a concern about the importation of cheap steel kitset houses.
"New Zealand has its own special characteristics in terms of geography, seismicity and climate, and we will need convincing that these characteristics can be adequately satisfied in the design and durability of these imported products."
NASH has invested heavily in design and engineering quality, Davies says.
"It will be very difficult for an offshore designer, engineer or manufacturer to match this level of experience and expertise to supply a structure of equal quality or integrity.
"The steel-framing industry in New Zealand is growing and has, together with Australia, an international reputation for innovation.
"A fact not widely known is that New Zealand is the largest exporter of Steel Roll Forming machines in the world," Davies says.
Coffey, from the NZTIF, says politicians bang on about the increasing number of unprocessed logs exported, and moan about value lost by not processing those logs in New Zealand.
"It is some of the same politicians who are now pushing for importation of kitset homes from Asia and this is a real slap in the face to the timber industry."
The cost of timber in frames for an affordable home new build is 4 to 5 per cent of the total cost. Timber frames and trusses are now 20 per cent cheaper than in 1994, Coffey says.
"We believe that the cost of using timber frames in a home can be further reduced by as much as 10 per cent."
He says having a home that is safest for a family is usually a primary concern, and timber fits the bill.
"With the information available about just how well timber copes in New Zealand's seismic conditions, it is hard to understand why all of the new building . . . whether it be in Christchurch, Auckland or Dannevirke, wouldn't include timber frames."
Those are fighting words, especially when you consider that steel-framed houses have also been found suitable to withstand a significant seismic event.
STEEL FAVOURED BY HOMEBUILDER
Torran Wiffen is wary of wet, rotting houses so when he wanted to build a new home he was drawn to the option of steel framing.
He says his family's five-bedroom home in Karori will cost about $400,000 to build, with the land costing a similar amount.
"Buying an existing house in Karori of that size would have cost over the $1 million mark. With this we can get what we want, and more, for under $800,000."
Wiffen will live in the home with his wife Rosalie and their two children. He was surprised at what he found when he started investigating steel-framed houses.
"Steel framing is strong, very, very straight, and won't twist or warp like timber will if it takes on any water. Steel won't rot either . . . and it isn't going to release any chemicals like [treated] timber.
"And it is a lightweight material, about a third the weight of timber . . . and is fire resistant. It doesn't add fuel to a fire."
Seismic strength was also important to Wiffen. "I didn't want a home with a wooden floor so was interested in a concrete slab. That's when I heard about Golden Homes."
Golden Homes is one of New Zealand's leaders in the construction of steel-framed houses. Its website claims that it has "never built a leaky home".
If Wiffen was to ever build another home from scratch - this is his first - he is unsure if he would consider timber framing. "I'll let you know in about four years' time."
Top five reasons to buy a new timber-framed home:
1. Provides a seismically safe home
2. More environmentally friendly
3. Superior thermal insultation
4. Natural electrical insulator
5. Ease of use building with timber
Top 5 reasons to buy a new steel-framed home:
1. Straight and square, does not warp/twist/absorb moisture
2. Fire resistant
3. Seismically safe
4. Provides a healthy home
5. Cost competitive
By the numbers
2002: Timber accounted for 98.1 per cent of the framing market
2012: Timber accounted for 87.8 per cent
Market share loss of 10.3 per cent in a decade.
2012: "Other" building materials, including steel framing, account for 12.2 per cent of the market.
Source: Building Research Association of New Zealand
- © Fairfax NZ News