Steel Frames - Steel Frame


	Rating 0-5 where is 5 is ideal	Timber Comment	Rating 0-5 where is 5 is ideal	Steel Comment
Skills Availability	5	95% of the building industry knows timber. Some Golden Homes franchises have now reverted back to offering timber.	1	Limited experience, let alone with additions/alterations. May need out-of-town steel builder.
Cost to build	4	Timber pricing has been relatively stable for many years. On average $2,000 less then steel house.	3	Based on international steel prices - variable. Steel house cost average $2,000 more then wood.
Thermal Insulation	4	Timber framing regulates house temperature, retains warmth in winter, cool in summer. Wood is 1.5 - 2x better then steel.	0	Steel allows heat to escape, more often requires timber lining. Latest report
Acoustic Performance	5	Absorbs sound. 400 times better than steel.	0	Transmits sound through steel, between rooms.
Environmental Impact	5	Timber framing is from renewable forests & absorbs 9.5 tonne of carbon in a typical house.	1	Mined, then requires a high CO2 energy to create steel, and recycle them. Typical steel house emits 4.5 t carbon to the atmosphere - equivalent to 2 year's worth of average household emissions into the atmosphere.
Health	5	Timber framing require treatment, although the boron typically used is also used as a health supplement, & pasture fertiliser.	1	Steel framing is treated with reactive metal zinc and a hexavalent chromium compound during the galvanising process. Heat loss may also affect health.
Movement	3	Slight in extreme climates.	4	Steel moves 2 to 3 times as much as wood with temperature.
Speed of construction	3	Fast with timber framing delivered on site, except where timber framing needs time to dry (insist on dry framing).	3	Steel is similar to timber, except where changes are identified during construction, which happens. Avoid roofing when steel framing is wet.
Durability (rot, rust...)	3	New rules require all Radiata timber frames and trusses to be treated/durable. Due to natural durability, Douglas Fir in certain low risk situations can be used without treatment.	4	Steel rusts where frames are cut, welded or scratched, or holes are drilled during construction.
Waste	4	Modern timber framing software creates little. Site waste often reused, burned or landfilled, where 97% carbon is locked up.	2	Little waste in steel, & can be re-cycled (at additional energy cost.)
Additions/alterations	5	Alterations are easy with timber framing, with plenty of skilled builders.	1	Alterations are difficult with steel, due to relatively few skilled builder options, resulting in possiable delays & costs. Steel has less flexibility for changes during the build process, & is normally done in the factory at the outset.
Suppliers	5	All builders & building companies use timber framing - competition keeps pricing down.	1	Few options, with typically 1-2 steel framing suppliers per province. Some of the Golden Homes franchisees in New Zealand had reverted back to offering timber framing.
Electrocution	5	No electrocution risk from wood & timber frames.	0	Rubbing of wires in holes in steel can electrocute where earthing is incomplete, or severed during earthquakes.
Social/economic contribution	5	Planting, forestry, harvesting & milling contribute to local jobs and value creation.	1	Iron ore shipped to China, re-imported as steel then rolled into frames adds little. Some ironsand is sourced from local beaches & milled at Glenbrook.
Fittings	5	Fittings are easy to hang on timber framed houses, compared to steel.	2	Difficult to hang as nails & screws cannot penetrate steel. Condensation can effect fittings, & holes drilled can create rusty steel.
Earthquake	3	Can absorb shock & resist earthquake damage. Simplier repair. Timber flooring & piles performed far better then concrete slabs in the Canterbury earthquake.	3	Steel is strong but less flexible. Welding repairs are more difficult, & skilled tradesmen rare. Where the steel framed houses bent in the Canterbury earthquakes they are far more difficult to repair.
Fire	3	Wood ignites at 250oC. Larger members char the exterior so remain unburned on the inside for longer.	3	Steel starts to melt at 230oC, but won't contribute to fire. Recently a fire that affected a steel framed house's bedroom caused heat distortion to the steel frames in the rest of the house. The insurance company initially refused to cover the whole house's replacement, and would only insure the replacement if built in timber.
Overall Rating (of possible 85)	68	80%	34	40%

Timber

Steel