Bias Alleged Against Wood

Press, Volume CX, Issue 32349, 15 July 1970, Page 20

Bias Alleged Against Wood

.New Zealand insurance companies appeared to be discriminating agaVnst timber-framed

partitions in houses and apartments without any statistical reasons, a Timber aid Fire Conferences organised by'the Timber .Development Association was told in Christchttrch yesterday.

In a paper on timber and its performawee- in fire prepared by Mt D. L. Evans, a consulting engineer of Rotorua, the conference was told that in order tn bring about fire-safe desigrt it was necessary to establish realistic firerating requirements ia. Now Zealand and apfOly them to structural elements. Mr Evans said that a test on a Douglas fir beam 27 5-Bin by 9in had .shown that

the beam retained 70 per cent of its initial strength after an hour’s exposure to fire with an average tempera-

ture of 1270 deg Fahrenheit By comparison, unprotected steel began to lore strength at 500 deg aqd high tensile steel at 400 deg. If exposed to the same heat as the wood beam, the steel would have been useful onfy as

scrap and aluminium would have begun to melt However, smooth-surfaced wood beams would not start

to flame until the temperature had reached lOOOdeg and' would char at only l-40in a minute. Moreover, because wood was not a good conduce tor of heat its temperature fin from the char zone was so low that there was practically no reduction in stress* Door Shown

Members of the conference were shown a door from the Dunedin Teachers’ College, which was badly damaged by fire in 1968. The door was made of red pine with an overlay of plywood on both sides.

The plywood veneer on the side facing the fire was badly charred but the body of the door proper was not damaged. A film produced by the National Timber Manufacturers’ Association of the United

States was also shown, where wood and steel beams were subjected to identical tests of fire and heat After 12 minutes of fire reaching ISOOdeg the steel beam collapsed; the timber beam was 80 per cent undamaged. The conference, which lasted for one day, was attended by insurance men, architects, engineers, representatives of fire boards, education boards and local bodies, and representatives of private firms connected with the building industry from all parts of the South Island. Opening the conference, Mr B. E. Mackenzie, of Christchurch, the vice-president of the Timber Development Association, said that many apparently non-combustible materials used in building were not what they seemed.

Four Papers In the morning four papers on aspects of timber and fire hazards were presented. It was important to break down large concealed ceiling spaces with fire-stop walls or baffiet Mr G. L. Smith, an Auckland architect said when presenting a paper on designtag for fire safety in Amber buildings. It was also necessary to install fire detection systems and shutters on ducts for heating, as these penetrated walls and thus made the spread'of fire easier. Smoke-stop doors were also 'a “necessary evil” and frequently in schools and hotels these were deliberately held 'open to give free access. One way of overcoming this might be electric eye systems, operated by fire detectors ’which would automatically shut the door. One way of stopping the spread of flames might be flSme-resistant paints, but more work had to be done on this, as moat so far used tended to mark easily' and did not wash well. Outlining the ffre-protec-

tion regulations for new buildings in New Zealand, Messrs G. Dunnachie and B. D. Cashin, both members of the Standards Association of New Zealand, suggested five changes that could be made. All timber wall - cladding which passed fire resistance tests should be at least 3/Bin thick; Combustible cladding should not be near any opening; Combustible cladding should be covered with noncombustible tiles above a certain height; Combustible cladding should not be allowed within a certain distance of another building (4ft in Canada); The total area of any openings, plus half the total area of combustible cladding, should not exceed the total area allowed for openings. Experimental work In the United Kingdom had also shown that the vertical spread of fire in multi-storey buildings through external openings was not significantly affected by the use of wood as external covering on panels under windows or in the areas round windows. The chairman of the Australian Fire Protection Association, Mr H. W. Marryatt, said, in a paper on the use of automatic fire sprinkling systems, that the stacking of timber in relation to processing buildings was important for toe safety in the timber processing industry. Timber stacks should be subdivided into minimum practicable areas and should be at least 30 feet from processing buildings. Even if automatic sprinkler systems were provided external systems should be arranged, particularly if there was storage within 30ft of an exposed wall.