TIMBER QUALITY TREATS
The timber treatment of roofing battens is fundamental to performance and longevity, so it’s something merchants need to understand.
with higher levels of moisture. Shrinkage will cause the tiles secured to the batten to come loose and possibly be blown off in high winds,” he continues.
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old and wet weather can play havoc on roofers and the projects they’re working. High rainfall and varied temperatures can both affect a roofer’s ability to work in the rain and the materials they work with. Merchants should be aware of the processes and know what to look for to guarantee the performance of the batten meets expectation.
Timber is a particularly absorbent material and without the correct drying method in place, the chemical treatment process won’t be as effective which is likely to impact the timbers performance and longevity. Shaun Revill, trading director at SR Timber explains that the storage of timber plays a key role in setting up for an effective treatment and grading process. “Depending on the conditions the timber is stored in, it can expand, and contract based on it being dry or wet. With graded roofing batten playing a vital role in roof construction, it’s vital this shrinkage is under control,” he says. Achieving the correct moisture content for graded batten can be accurately monitored via kiln drying, which ensures the timber dries to a set moisture content. “Reaching the correct moisture levels will also ensure the treatment process is properly carried out and sufficient retention is achieved. Equally as vital, the treatment process gives the batten the correct service life against insect attack, rot, and decay - especially vital when installed above damp course level,” Revill continues. He says that, with the presence of substandard and counterfeit batten still in
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the market, manufacturers, importers, and distributors including SR Timber are doing their part to highlight the presence of this unsafe and inferior material being sold as fully graded roofing batten.
At production stage, a critical process for turning timber to batten is how it’s dried. Revill says: “Roofing batten shouldn’t have a moisture content exceeding 22% at the time of fixing. Batten produced from wet timber is likely to have a moisture content substantially higher than the maximum level. This type of material is prone to shrinking in situ, with tiles or slate becoming lose as a result which will impact the overall performance of the roof.” An important standard to consider when working with timber is BS 8417: Preservation of Wood. This gives recommendations and guidance for the preservative treatment of wood, stating that excessively wet or dry can be more difficult to impregnate. Wood should be treated at, or as close to, its expected in- service moisture content which is typically less than 30%. Roof timber should be treated to Use Class 2 as a minimum, which when in situ covers risk of wetting.
If the batten hasn’t been produced from kiln dried timber, then when this ‘wet’ batten is delivered for treatment in freezing temperatures, the excessive moisture is likely to frreeze, and will prevent the treatment process from being carried out correctly, compromising the battens service time. “The very real consequence of this process is when temperatures rise, and the improperly treated batten dries out having been installed
This warning goes hand-in-hand with the current recommendations to check batten is graded to British Standard 5534. Quality is fundamental to timber roofing battens for a pitched roof installation and that quality carries through from treatment to grading. Revill adds that it is a requirement of the code of practice for battens to be stamped with information identifying supplier (manufacturer) details, dimensions, imported and/or species code, and the wording ‘Graded BS 5534’. It’s also highly recommended to include the third-party certification of conformity.
Merchants can advise their customers to do four quick and easy checks to ensure quality: l Size – a good quality batten will be consistent in sizing on both thickness and width. BS 5534 allows for a tolerance of -3mm /+3mm on the width (38mm/50mm) and for -0mm/+3mm on the thickness (25mm) l Markings – ensure the markings are in place on each piece of batten l Due diligence – all documentation shows correct information and batten carries chain of custody certification l Knots – check the size of knots look okay. “Many businesses are taking measures to maintain and grow margins in an increasingly difficult market, and while it may be tempting to opt for cheaper roofing batten, the savings aren’t worth the risk,” Revill continues. “It would only take a single batten to fail and bring out serious consequences for the businesses involved in selling such inferior and unsafe battens. Our recommendation will be for merchants to carry out the proper due diligence on the batten bought to ensure both quality and safety. Check for full evidence of correctly graded roof batten, as well as treatment certificate and chain of custody certification to cover legality and sustainability.” BMJ
www.buildersmerchantsjournal.net April 2023
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