Preservative treated timber

Online since 5.09.2017 • Filed under Advertorial • From Issue 6 - September 2017 - February 2018 page(s) 44-45
Preservative treated timber

SA Wood Preservers offers advice about treating timber and the types of wood preservation and their hazard classes for end-use applications.

The natural durability of South Africa’s commercially-grown species – such as Pinus and Eucalyptus – is low, rendering it susceptible to insect and fungal attack. It is important to treat the timber with a wood preservative.

There are two types of wood preservation – primary (industrial) and secondary (DIY). In primary preservation, wood is impregnated (pressure treated) with an industrial chemical wood preservative, such as CC A, TBTN-P, or creosote. This process increases the long-term durability and resistance to fungi and insect attack. Primary preservation is prescribed in South African National Standards (SANS), NRC S Compulsory Specifications and Building Regulations.

Secondary preservation is a surface application used for supplemental (preventative) and/or remedial (corrective) purposes and applied by hand, for example for treating previously untreated timber or exposed ends of machined pressure-treated timber. Protective wood sealers or varnishes are not regarded as secondary preservatives unless they contain active ingredients (biocide). Without active ingredients, such finishes merely protect against weathering (moisture and UV rays), and not fungal and/or insect attack.

Primary preservation of timber is categorised into different hazard or ‘H’ classes for different end-use applications: ground, fresh water or marine applications). Apply a suitable penetrating wood sealer and regularly maintain it if a natural non-weathered look of the exterior timber is desired.

H Classes Preservative Types Typical End-Uses Protection Against
H2 - Dry Interior above ground

CCA, CuAz, ACQ and Boron


Roof trusses

frame wall construction

interior doors and joinery

Insect attack and low decay risk
H3 - Exterior above ground



Decking, cladding, exposed structural Fungal attack and insects
H4 - Exterior in ground



Timber used in ground; poles used in light structures, fencing, landscaping and garden features Fungai decay and insect attack
H5 - Fresh wate and heavy wet soil contact



Jetties, walkways, poles/posts used as foundation support in permanent timber structures
H6 - Marine CCA plus Cresote Jetties, Quarys, Marine walkways, retaining wall and barriers


How to plant a pole/post

When planting a pole or post, do not plant them inside an encapsulated concrete base. Instead, use a collar or compacted stone and soil with or without a solid (cured) concrete base.

As a safety precaution when machining CC A-treated wood, wear a dust mask, gloves and safety glasses to protect your eyes. Do not make baby toys, furniture, food utensils or store food or water in containers made from CC A-treated wood. CC A-treated wood should also not be used in beehives.

Treated wood waste is not regarded as hazardous waste material and should either be reused for applications where treated wood was intended, or be disposed of at a registered disposal or landfill site. Do not burn treated wood off-cuts and do not use it for firewood or for food preparation. Do not use treated wood shavings and sawdust as mulch in gardens, or for animal litter or bedding where it may become a component of animal feed.

For more information about wood preservation in South Africa, please visit

Issue 6 - September 2017 - February 2018

Issue 6 - September 2017 - February 2018

This article was featured on page 44-45 of SABI Magazine Issue 6 - September 2017 - February 2018 .

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