timber treatment alternatives organicnz jul aug 08

7/27/2019 Timber Treatment Alternatives Organicnz Jul Aug 08

1/4ORGANIC NZJuly/August 2008 Promote Educate46

Building

For the last 70 years merchants around the world have

been infusing timber with chemicals to increase their

durability. Fortunately the last ten years has given

us not only a new generation of slightly better treatment

choices but also a renewed understanding of some traditional

chemical free alternatives.

This level of understanding and acceptance has not yet

been absorbed adequately across the industry, and a huge

amount of serious misinformation exists. Read on to discover

some of the myths, educate yourself on the facts, and armyourself with all the options so you can make the best

decision for your situation.

Timber Treatment

New Zealand building regulations nominate durability

requirements for specific areas within buildings, from an

expected lifespan of just five years to a mandatory minimum of

50 years. How we achieve this is to some extent up to us.NZS

3602 Timber and Wood Based Products for Use in Building,

is one document that councils refer to when assessing your

building consent application and actually provides a fair

degree of choices including non-chemical alternatives, if

youre willing to point them out to sometimes uninterested

building inspectors.

Treatment requirements range from H1.1 to H6, which

is actually a reference to the chemical hazard classificationbut serve us as an indication of the durability of the timber

and therefore its suitability for different applications. Refer

to table 1.

The chemicals that plant operators use to achieve this

durability varies. As a consumer you are able to identify

the chemical type and its level of durability by checking the

branding on the end of the timber. Each piece of treated

timber bears a branding mark to identify the plant responsible

for its preservative treatment, the preservative code number

(chemical type), and the treatment class or level of treatment

the timber has received, listed in that order. See table 2.A third generation of benign, or organic treatments are

rumored to be in the laboratory pipeline but until they are

available lets look at the current options.

Copper Chrome Arsenate preservative (CCA)

Unfortunately NZ still allows the use of CCA (copper chrome

arsenate) salts, and oxides, when other countries have long

since fazed them out because of toxicity concerns.

CCA may no longer be used in Australia when intended

for use as garden furniture, picnic tables, exterior seating,

children play equipment, patio and domestic decking boards,and handrails. Some countries have issued a complete

Timber TreatmentTimber Treatmentand yourand your AlternativesAlternatives

Table 1. Applicability of Different Timber Preservatives

Hazard

Class Typical Use CCA

ACQ

CuAz

Boron

LO

SP

H1.1 Interior finishing timber

H1.2 Wall framing

H2 Not used in NZ termite protection

H3.1 Cladding, fascia, joinery

H3.2 Decking, posts

H4 Fence posts, landscaping

H5 House piles

H6 Marine applications

* A number of different LOSP mixtures are covered under this heading,

and not all mixtures are suitable for all the indicated hazard classes.

Source: CCA review 2005 by Dr B Graham.

Tina Booth asks: Is a chemical free home a viable possibility or the holy grail of eco building?


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Building

July/August 2008 ORGANIC NZAdvocate Connect 47

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blanket ban on CCA and others

restrict their use to commercial

applications only, or where human

contact is unlikely. NZ government

has only gone as far as a byline

warning in some publications,

advising against their use in

situations where children may

touch the treated wood.

CCA treatment is still used

in NZ in all hazard classes, even

though there are other less toxic

treatments available for H1.1

through to H5. It is up to the

consumer to check which treatment has been used on the

piece of timber they want to purchase and to pick accordingly.

At this point in time, we have limited choice when it comes to

timber requiring durability levels H4 and H5. Unless we can

procure a CAF (copper and arsenate free) treatment such as

ACQ (see below), which is difficult to come by because of its

expense, we simply have to use CCA treatment or preferably

design our structure to not need them. CCA is the only

treatment available in NZ for timber requiring H6.

Borate preservatives

These contain boric acid, oxides and salts and are used widely

throughout the world. The preservative is not fixed in thetimber and therefore leaches easily. It is considered to have

a low toxicity to humans. Treatment for level H1.1 and H1.2

only.

Alkaline copper quaternary

preservatives (ACQ)

ACQ is the most widely use alternative

to CCA, as it is free of chrome and

arsenate. Its suitable for all applications

requiring H1.1 to H5 timber. However

ACQ treatments contain high levels

of copper salts and didecyldimethyl

ammonium chloride (DDAC) to

displace the chrome and arsenate

found in traditional CCA. The copper

content makes the timber highly

corrosive (some research indicates ten

times more corrosive) therefore double

dipped galvanising or stainless steel fixings are necessary.

DDAC is highly toxic to fish and other aquatic organisms,

but is believed to have only moderate acute toxicity to

humans. Although still toxic, this is by far the best product to

use where H4 or H5 are unavoidable, but difficult and pricey

to obtain.

Light organic solvent preservatives (LOSP)

White spirits are used as a carrier to deliver preservative

compounds into timber. Although this formulation contains

no heavy-metal compounds, there are still serious warnings

regarding its use. Some people may experience health

problems, such as skin rashes, eye irritations, headaches orlight-headedness and nose bleeds when working with this

timber.

Formulations containing tributyltin (TBT) compounds

Table 2.Chemical Codes

CCA oxide 01

CCA salt 02

Boron, Boric 11

TBTO (losp) 56

Copper naphthenate (losp) 57

Copper azole (CuAz) 58

TBTN (losp) 62

IPBC (losp) 63

Propiconazole+ tebuconazole (losp) 64

Permethrin 70

Alkaline copper quaternary (ACQ) 90


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Building

July/August 2008 ORGANIC NZAdvocate Connect 49

are banned as a timber treatment by the U.S. Environmental

Protection Agency and also in other countries. TBTs are a

toxic, corrosive fungicide known to be harmful to aquatic life

in amounts as low as a few parts per million. Permethrin is

used as an insecticide even though it is a known neurotoxin

and carcinogen. It is highly toxic to honey bees, beneficial

insects, and aquatic life. For many species, concentrations of

less than one part per billion are lethal. However this is the

same ingredient used in many head lice treatments that we

routinely use on our school age children.

LOSPs can be formulated for uses H1.1 to H3.1 or ( H3.2

for CuN only ). The NZ government has been lobbied to

restrict its use to H3 and above -if not ban it all together - with

more pressure placed on them since builders have reported

coughing up blood. One national chemical supplier has

discontinued the supply of this product as less toxic options

are available and in their opinion should be supported.

Copper Azole preservatives (CuAz)

Copper Azole is a water-based wood preservative that prevents

fungal decay and insect attack; a mixture of copper salts and

a triazole fungicide, -tebuconazole. It has low acute toxicity to

humans, but is noted as a possible human carcinogen. It has

come into wide use in the USA, Europe, Japan and Australia

following restrictions on CCA. It can be used in situations

requiring H3.1 to H4.

Chemical Free Alternatives

New Zealand has a fairly diverse planting of trees across the

country, so it is not necessary to rely solely on Radiata Pine for

our buildings. Although the mainstream building merchants

may stock pine almost exclusively there are other stockists and

sawmills who do routinely deal with other species. Supply

of these alternative timbers may vary from time to time and

will probably have a direct impact on their moisture content.

Most untreated timbers allowed by the NZS are required to

be dry, with moisture content lower than 18%. All timbers

listed in the code are referred to by their grading. This is oftenthe downfall of smaller owner operated sawmills, as they may

not have a trained timber grader to check and ensure that

what they are selling is actually suitable by law.

The following species are a sample of our most commonly

available and suitable timbers. This list is not intended to be

exhaustive; rather it lists the species mentioned and accepted

within the limits of NZS 3602. The NZS also recognises other

timbers even though they may not be mentioned by name in

the standard, but its usually up to you to convince the local

body council of its suitability for your use.

Radiata Pine Structural, No 1 and No 2 framing gradedpine can be used untreated if its kiln dried and machine

gauged for situations such as interior framing, mid floor

joists, some roof trusses, internal finishing timbers and

some exterior wall framing depending on cladding type.

Other Pinus species are acceptable in some cases, check

NZ3602.

Eucalyptus Species Includes E.botryoides, E.saligna,

E.globoidea, E.muellerana, E.obliqua, E.pilularis.

This is generally a very hard timber, great for decking and

flooring. Structural graded sapwood can be used in place

of timber requiring treatments H1.1 and premium grades

such as A, structural or dressing grade heartwood can be

used to replace pine requiring H3.2.

Cypress Species Includes Lawson Cypress, Cupressus

Macrocarpa and Mexican Cypress.

These species are a moderately durable timber and can be

placed in similar situations to eucalyptus. Cypress is softer

than eucalyptus and often preferred as its easier to work

with. Use the sapwood grades in situations requiring H1.1

and H1.2 and the premium heartwood grades in place of

pine usually requiring treatment up to H3.2.

Douglas fir Douglas fir can be used in place of untreated

pine and pine requiring H1.1 level treatment. It is a

stable timber, suitable for beams and framing (other than

exterior bottom plate) where there is no risk of trapped

moisture.

LarchThis is deemed slightly less durable than the eucalyptus

species in the eyes of the NZ timber design journal but asslightly more durable in the NZS3602. It is suitable for a

reasonably wide range of applications. Structural grades

can be used as general framing, roofing members and

truss construction, sub-floor and mid-floor joists, and

finishing timbers.

Vitex and Kwila Both species are imported. Kwila is not

recognised as a sustainably grown timber and is best

avoided to prevent deforestation in other countries.


4/4ORGANIC NZJuly/August 2008 Promote Educate50

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More informationCopies of the Timber Treatment Guide published by

the Department of Building and Housing can be

downloaded or ordered via their website

www.dbh.govt.nz.

For more technical information on treatment regulations

refer to NZS 3602: 2003 Timber and Wood Based

Products for Use in Building. Available from most

public libraries or purchase your own copy from

www.standards.co.nz.

Vitex is touted as the new eco friendly hardwood that has

a creamy light colour. However it is imported and even

though it may be grown sustainably, if there is a suitable

local timber, your best eco choice lies there.

Cedar and Redwood Both cedar and redwood are

dimensionally stable, preferred timbers for weatherboards

and joinery.

As suggested earlier there is a lot of misinformation out there.

For example while researching this article, one chemical

supplier seemed deeply offended when questioned about the

toxicity of some timber treatments, he swore nothing had

been proven. A treatment plant operator warned us not to

use any other treatment as CCA was the only product with a

50 year guarantee. Yet another unqualified timber salesperson

categorically stated that by law you must use CCA treatment

throughout your house.

All these statements are wrong and misleading to the

individuals who may trust advice from so called professionals

in the industry. The author has successfully used and specified

many alternative chemical free timbers in eco homes she

has designed, along with the hundreds of homebuilders

throughout our history prior to the invention of timber

treatment.

Now that sustainability and green considerations are

talked about a little more openly, and not referred to as the

sole domain of barefooted hippies, we are free to make healthyinformed decisions, without bias, if we choose to.

You may still meet resistance and ignorance even in the

building trade, perhaps especially so, but know that you do

have legal and documented support.

Tina Booth is an Architectural Designer specializing in green homes and

frequently writes for magazines on sustainable building and business

topics.

timber treatment alternatives organicnz jul aug 08

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