New Guidance on cutting roof tiles with cutting discs


The HSE has worked with the National Federation of Roofing Contractors (NFRC) to produce a new guidance sheet to inform and train those who have to cut roofing tiles to size – an innately dangerous process in several ways if it is not properly controlled and safeguarded. The HSE requires roofing contractors to follow the new working methods from 1st October 2012. Therefore, please study this outline and consult the fuller documentation from the NFRC.

What are the specific hazards?

Respirable Crystalline Silica (RCS) is released when with concrete and clay roof tiles are cut, especially when carried out using high-speed cutting discs. Water suppression is required to damp down the dangerous dust: this also applies to all roof tiles, artificial slates, concrete slates etc. If contractors use other methods then they must show that these are equally effective in controlling the risk. (Hand cutting is recommended where possible but in a commercial environment it may not always be economically viable).

Because roof tiles often need to be cut in roof verges, ridges, hips and valleys a hand-held disc cutter saw has been used instead of a wet cutter that is usually stationed at ground level. Disc saws produce large amounts of silica-containing dust which can build up in, and be very harmful to, the lungs, causing lung cancer, silicosis and Chronic Obstructive Pulmonary Disease (COPD).

It is therefore subject to the Control of Substances Hazardous to Health Regulations (as amended) 2002 (COSHH), which limits the amount of silica dust that someone can breathe.

The former interim agreement between HSE and the industry was to use water suppression and respiratory protective equipment (RPE) for the cutting of all roof tiles except for valleys, where wet cutting these tiles created a number of difficulties that some felt could not be effectively overcome at the time.

HSE testing showed that the levels of silica dust created by dry-cutting valley tiles was much higher than the safety limits, which have to be very low. HSE therefore wants a high standard of control for cutting all roof tiles, including valleys.

Controls by roof tile type

The following ‘reasonably practicable solutions’ are given for controlling silica exposure in each area.

Verge Tiles

Where possible, avoid cutting by using ½  or 1 ½ size tiles. If cutting is needed, mark the tiles and cut away from the roof on the scaffolding using water suppression and RPE as per ‘Wet cutter use’ below.

Openings and Abutments

If cutting is needed, mark the tiles and cut off the roof surface on the scaffolding as above.

Ridge Tiles

Where variable-gauge tiles are used, cutting can be done on just a small number of the covering ridge tiles. Where fixed-gauge or restricted-gauge tiles are needed, the top course may also need cutting to length, so mark these tiles and cut on the scaffolding as above.

Hip and Associated Tiles

The roof tiles at the rake of the hip will all require cutting. In many cases this can be done on the roof, using hand tools. Where machine cutting is needed for difficult cuts or for a neater, cleaner cut (e.g. some dry fix systems), mark the tiles and cut off the roof surface as above. Where two people are working, one person can mark the tiles while another cuts. Alternate the process to reduce each person’s exposure and eliminate off-cuts being left to slide down a roof and becoming a slip/trip hazard.

Valley Tiles

As with the hip, there is a need to size each tile to the internal angle. Methods vary but generally, set tiles back from the valley and mark them using the covering width of one or more tiles to establish the cutting line. Longer valleys may need a mid-point to maintain accuracy when striking. Number the tiles with chalk or a pencil, remove any nibs likely to kick the tiles, and cut on the scaffolding as above. Cutting tiles individually, not in-situ, may result in slight alignment issues between courses but marking and cutting back should create a valley which is adequately straight over its length, and will be dust and defect-free.

The number of roof tiles that will need to be re-laid can be minimised by staggering tiles or by cutting tiles individually rather than in sets. More time may be needed to complete the valley than when cutting in-situ. But see the benefits listed below.

Wet cutter use

Always use water suppression when cutting a tile with a cut-off saw. Effective dust suppression requires a flow rate of around 0.5 litres per minute (unless manufacturers say otherwise). A portable polypropylene hand pump bottle of around 8 litres is the simplest way of supplying water. Re-pressurisation is needed about every 4 minutes of use.

Follow these wet cutting guidelines:

  • Water must always be available at all times. Measures must exist for refilling hand pump bottles: or use a permanent water supply.
  • Planning is required to prevent excessive handling of the tiles.
  • A dedicated cutting area(s) on the scaffolding should be established before work starts. It is vital that the integrity of the scaffold boards is not compromised by cutting. Sacrificial material must be placed between the tile and scaffold board.
  • Unless mechanical lifting aids are used, HSE advises against cutting on the ground. There is an increase in the risk of falls and manual handling when moving the tiles down and up again.

Respiratory Protective Equipment (RPE)

RPE is essential to silica dust control. It should be used for all tile cutting activities even where water suppression is employed. Workers assisting tile cutting, nearby on the roof or the top lift of the scaffold must also wear it. Workers away from the dust cloud do not need it.

A. Disposable / Half Mask respirators

Half masks (disposable or orinasal) are probably the most common type of RPE used in tile cutting. Masks with an assigned protection factor of at least 20 (i.e. a FFP3 filtering facepiece for disposable masks or an orinasal half mask respirator with a P3 filter) should be used. This high performance RPE should be worn for all tile cutting.

  • Disposable masks should be replaced every shift or when damaged.
  • Orinasal filters should be renewed frequently dependant on use; probably at least weekly.

Spares should always be available. They need suitable storage arrangements and a monthly thorough examination and must be tested by a competent person.

Successful face fit-tests are crucial to ensure that the users can be protected, or they may receive no or little protection. Fit test providers should be competent (e.g. accredited under the Fit2Fit scheme)

Wearers should be properly instructed, trained and supervised on the correct use of the equipment. Wearers must be clean-shaven and the mask must be fitted and worn correctly for the full duration of the tile cutting activity. Where these factors are not implemented, protection will be lost.

B. Powered Respirators

A “loose-fitting” type of respirator (e.g. powered hood, helmet or visor) should be worn by workers who have beards or cannot get an adequate fit using disposable or orinasal half masks. Models incorporating head and eye protection can also be selected. These should be to a protection factor (PF) of 20 and a TH2 classification.

Again the users will require adequate information, instruction and training in the correct use of the chosen equipment. Storage and maintenance arrangements are needed including a monthly thorough examination and test by a competent person.

Training and Involvement

Appropriate training and information must be given to workers who cut tiles. This should include awareness about the risks, the precautions required, how to effectively use water suppression and the use and maintenance of RPE. Ensure appropriate worker engagement and consultation as part of this process.

Benefits to off-roof cutting

The new guidance feature is the need to wet-cut valley tiles. As the authors admit, ‘significantly more time may be needed to complete the valley’ – but they point to these advantages:

  • Using water significantly increases the life of blades and prolongs the lifespan of the saw motor.
  • No need to rough cut first.
  • Less risk of cut tiles breaking during cutting (and having to be re-cut).
  • Off-cuts can be saved and re-used on any hips on the roof (or other roofs), saving waste and money.
  • The Concrete Tile Manufacturers Association (CTMA) does not recommend cutting valley tiles in situ because it can make slits in the liner. Dust or slurry can get into and weaken the mortar, and there may be a loss of bond from the vibration. An NHBC study into pitch roof claims found that over half were due to mortar defects. Repairing damaged valley mortar is expensive as scaffolding or other edge protection is often needed.

Dry Valleys

  • There is a trend towards using dry valleys. Where possible, NFRC encourages these instead of wet valleys, where mortar can fail. The other benefits are:
  • Dry valleys cannot be cut in-situ, so wet cutting off the roof is no problem.
  • Cuts do not have to be quite as precise as in open valleys.
  • Dry valleys are maintenance free.
  • They can be installed in cold weather, allowing work on more days in the year.

Should you need any guidance, then please consult with the Health and safety Official for your organization.