If you are considering specifying a timber preservative for either remedial or pretreatment, the first and most obvious question to ask is: is it necessary?
The last 40 years has seen the mass production of some highly toxic synthetic insecticides and fungicides which have been supplied to the remedial and pretreatment industries. Much of the application has been to prevent or remedy the premature decay of timbers resulting from poor design, inappropriate timber useage and inadequate maintainance of buildings.
The timber treatment industry has expanded massively and is now a significant sector of the building industry, with, we would suggest, its own vested interests. Thousands of timber preservation companies place around 100 tons of toxic chemicals in around a million buildings each year (source: AECB). Remedial treatment is still undertaken almost routinely, at the slightest sign of any timber biodeterioration, with treatment often a condition of a mortgage offer. Pretreatment is still routinely specified in buildings where it is difficult to see it as any more than a 'belt and braces' measure.
Establishing the 'need to treat' underpins British Standards (BS5589 & BS5268 part 5), something that is easy to overlook!
BS5268 Part 5 prioritises good design and appropriate timber use: "where design is unlikely to provide adequate protection, a naturally durable timber or the use of an appropriate preservative treatment should be considered".
A more rigourous process of establishing the need to treat will not of course eliminate chemical treatment of timber, but should much reduce the amount of chemicals introduced into buildings. A smaller, more rigourous and more environmentally sensitive timber treatment industry could continue to play a vital role within our buildings, old and new.
For more information on this issue, please take a look at about ordinary timber preservatives and issues of safety, efficacy and the environment and boron timber preservation. We also publish two articles on the subject, written by our directors for the AECB during the 1990s, to be posted here soon.
These principles are in accordance with the those of the Association for Environment Conscious Building. Where it is established that a chemical treatment is required, a boron preservative will almost always give the safest and most benign option. For more information about the range of boron timber preservatives offered by Green Building Store, please click here.
Pretreatment For new or replacement work, the careful selection of timber species, coupled with good design and building practice, can eliminate the need for chemical treatment. New wood from Durability Classes 4 & 5 (EN 350), Non-durable and Perishable, may require treatment when used in exposed situations such as windows, doors, roof tile battens, fascia boards etc. In particular the requirements of the current Building Regulations should be noted. Wherever possible, pretreatment with inorganic boron compounds should be considered, as the safest and most environmentally sensitive option.
Windows and doors from the ecoplus system range are pretreated with a glycol borate, for maximum penetration, safety and environmental sensitivity. To find out more about the range, click here.
Inorganic borate pretreated roof tile battens, fascias etc may be available in certain parts of the country. The AECB may have information on current availability. Tel 01559 370908 (members).
For most applications, timber of any durability class does not require treatment for internal carpentry or joinery.
Treatment should only be considered in high risk areas, for example where there has previously been heavy infestation of the dry rot fungi or where death watch beetle may be a particular problem.
Remedial treatment Renovation work frequently uncovers some degree of rot or insect attack to existing timbers. To some extent of course the approach to this will vary depending on the circumstances. Dealing with timber decay in a Grade 1 listed building will be a somewhat different proposition from a modern town house.
The principles should be the same, however.
Establish the cause of the attack.
Rectify the causes, by adjusting temperature, ventilation, defects to the building structure etc.
Consider whether further measures are necessary.
Where further measures are considered necessary, there are companies which specialise in the environmental control of fungal and insect attack in timber without the use of any chemical treatments. This may be most appropriate in sensitive properties and conservation work. Where timber replacement is required, this can often be undertaken conservatively by the use of resin splice repairs in conjunction with boron treatment. This method has been used very successfully on many listed buildings, as well as in more modest properties. To find out more, search the AECB membership list for the Environmental Control of Timber Decay Services or Environmental Monitoring here.
Some remedial treatment companies do train their operatives to use safer boron base chemicals, and to use more conservative measures. To our knowledge, one company, Remtox, offers the installation of anobium traps to ascertain if woodworm (anobium punctatum) is currently active. Two companies that we are aware of (Remtox & Safeguard) offer the option of treatment with boron compounds (which should be inorganic). Where companies and installers are AECB members they can be found through the membership list searching for Building Services or Product Manufacturer, here.
Specifying a chemical timber pretreatment Where a simple 'brush on' (or spray on) treatment is considered necessary, Green Building Store has a solution. Guidance on the durability of different timbers is available in many reference works, from TRADA or BRE publications, or by referring to BS5589 or EN350.
Some suggested solutions:
Application: sawn pine (Durability Class 4 - non durable) weatherboards Treatment: two coats of Borax Timber Preservative to 10 m2/L; finish with an external woodstain system such as OS Color One Coat Only or Country Colour
Application: joinery items such as windows, doors etc after fabrication, manufactured from non-durable (Class 4) timbers such as Redwood or Douglas Fir Treatment: one flowing brush coat of Boracol 20; finish with an external paint or woodstain system such as OS Color One Coat Only or Country Colour
Application: vulnerable areas of non-durable sawn structural posts, above ground. Treatment: two coats of Borax Timber Preservative to 8 m2/L; finish with an external woodstain such as OS Color One Coat Only or Country Colour
Specifying a remedial timber treatment Where a remedial treatment is to be specified, consider the Boracol range. Boracol 10, 20 & 40 offer a complete solution to remedial treatment of insect and fungal attack. They are in the only class of preservatives which can eliminate Dry Rot (merulius lacrymans) in situ. They also offer far greater penetration than other timber preservatives - up to 40 mm in sound dry pine.
For further information on remedial treatment of fungal attack with the Boracol system, please email us, or call 01484 461705.
