26 October 2015

The importance of roofing battens is often overlooked in the overall build-up of a roof.  Roofing battens are a structural timber and are designed to have adequate strength to support the dead (ie roof covering), imposed (any additional temporary load) and wind loads. They may also be used as an alternative to roof ladders or provide a secure foothold in line with guidelines and current health and safety advice.

Health and Safety when working at height

Planning for safety is key! Most re-roofing jobs will fall outside CDM regulations but there should still be a full method statement and no ‘ad hoc’ work. Care should be taken that any materials should not create any additional hazards for future maintenance. Contractors should be able to demonstrate they have current and sufficient skills and knowledge of the latest standards and materials to enable work to be carried out safely.

The main risk associated with defective or sub-standard battens are falls from height. Are battens being used as either as a ladder or as a foothold during roofing works? If so you must ensure that you meet the HSE guidance and that you’re using the right batten. The batten must be graded to BS5534 and installed in accordance with current standards.

The use of ungraded battens can put the safety of the operative at risk, which can put the contractor at risk for breach of his ‘Duty of Care’.

Structural strength and performance of the roof

Poor quality battens means that the roof may not be meet current standards or comply with specific product guarantees. It may not be possible to secure adequate mechanical fixings into such battens or they may not adequately support tiles, slates or other roof loads. Unseasoned timber could shrink below minimum dimensions and fixings or clips may then not be properly installed.

Getting it right

So how do you make sure your roofing project is safe, not just during installation but that the finished job is worthy of your reputation and won’t result in unnecessary remedial work.

All defects can compromise batten quality but here are the 5 real problems to look out for on-site.

Knots

Through knots are one of them most dangerous defects of a roofing batten. Any pressure on a batten with a through knot will cause the batten to break, and often these weaken the batten enough that it will break simply by picking it up.

Knots must adhere to a particular measurement as follows. For 25 x 38mm battens – the sum of the width of the knot on the top and bottom face of the batten must not exceed 38mm. This carries through for 25 x 50mm battens so that the sum of the width of the knot on the top and the bottom face of the batten must not exceed 50mm.

Wane

Wane is when the batten is not square. This is typically because the edge of the tree has been used. Wane is permitted, but on one arris only. The size of the wane should not exceed 1/3 of the width, of each of the faces on which it occurs.

Dimension

Accurate dimension is crucial to the batten integrity. All battens should be 25mm thick as a minimum. There is a -3mm tolerance in the width to allow for manufacturing processes.

Distortion

Battens that are not straight are not safe and can’t be easily installed. Battens that are cut from side boards are unlikely to distort. Battens from centre cut, especially if there is pith (the centre of the tree) easily distort. Bow, spring or twist should not be greater than 5mm, measured over a length of 1.2m at reference moisture of 20%.

Fissures & Splits

Typically fissure and splits appear at the end of the batten (even in fully graded battens). These should be cut off when fixing to ensure the structural integrity isn’t compromised.

So, choose your batten wisely. Saving £12 on a typical roof for lower grade batten may seem like a good idea at the time but what will the real cost be to the job if the batten fails. Buying a batten that is graded to BS5534 is the correct batten for all roofing work.

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