How to Cut Fibre Cement Cladding Safely

To cut fibre cement cladding such as Cedral cleanly and safely, use a circular saw fitted with a diamond (PCD) blade for long or repeated cuts, or a jigsaw with a fibre cement blade for notches and shaped cuts. Cut from the back of the board, cut only when the board is dry, control the dust at source with on-tool extraction, and wear suitable respiratory protection.

This guide covers the tools, the dust risk and how to manage it, where to cut, what Cedral says about treating cut edges, and how to drill and fix close to the ends of a board.

Which tools cut fibre cement?

The Cedral fixing guide says the right method depends on how much cutting there is to do, and that Cedral can be cut with a handsaw, a guillotine, an electric jigsaw or a circular saw.

Circular saw with a diamond blade (recommended for most jobs)

For larger quantities, Cedral recommends a hand-held circular saw with a fibre cement blade, and specifically a diamond-dusted blade. The fixing guide recommends a 4-tooth blade of 180mm diameter. It also advises cutting from the back of the board, because the saw guide can mark the face, and recommends making a test cut first.

We sell the Profi diamond saw blade for fibre cement, which has polycrystalline diamond (PCD) teeth and a 20mm bore. It comes in several diameters to suit different saws, from £29.18 ex VAT at the time of writing. Check that the size you choose matches your saw before ordering.

Jigsaw (for notches, cut-outs and shaped cuts)

A jigsaw is the practical choice for cutting around pipes, window details and other awkward shapes. Cedral's guidance is to turn the board over and cut on the reverse, which gives a clean finish on the front face. Use a blade made for fibre cement: our Profi fibre cement jigsaw blades are tungsten carbide, 100mm long with a 75mm working length, and cost £8.17 ex VAT for a pack of three at the time of writing.

Guillotine

Cedral notes that a purpose-made fibre cement guillotine can be used, but recommends it for Cedral Lap only.

Dust and silica: the health risk

Cedral's fixing guide warns that cutting releases dust that can irritate the airways and eyes, and that long-term exposure to dust can be harmful to health. It refers installers to the product safety data sheet in the technical section of cedral.world, and you should read it before you start.

Cement-based building materials can release respirable crystalline silica (RCS) when they are cut, drilled or sanded. The Health and Safety Executive (HSE) says regularly breathing construction dust can cause diseases including lung cancer, silicosis, chronic obstructive pulmonary disease (COPD) and asthma, and that these diseases cause permanent disability and early death. HSE guidance gives a Workplace Exposure Limit for RCS of 0.1 mg/m³, averaged over 8 hours.

How to control the dust

HSE's construction dust guidance asks employers to assess the risk, control it and review the controls, under the COSHH Regulations. For power-tool tasks, HSE's COSHH essentials sheets for construction combine dust extraction and/or water suppression with respiratory protective equipment (RPE). Masks are a backup to controlling the dust at source, not a replacement for it.

Cedral advises against cutting boards when they are wet or damp, because the cutting dust sticks to the board and can stain it. That makes water suppression a poor fit for Cedral, so on-tool extraction connected to a suitable extractor is the practical way to control dust at source. HSE's information sheet CIS69, Controlling construction dust with on-tool extraction, explains how to choose and maintain an extraction system.

• Use on-tool extraction on the saw wherever possible, and keep the hose, shroud and filter in good condition.
• Wear suitable RPE. HSE says tight-fitting facepieces must fit the wearer's face to be effective, so each wearer should be fit tested. HSE also says stubble and beards make a good seal impossible. If you have a beard, use RPE that does not rely on a tight fit.
• Protect your eyes, because the dust can irritate them.
• Clean up without raising dust. Do not dry sweep or blow dust away.

If you are employing others or running a site, read HSE's construction dust guidance in full. Your duties under COSHH go beyond what we can cover here.

Where to cut: dry, ventilated and away from the wall

Cedral's fixing guide says cutting and drilling must take place in a dry, well-ventilated environment. In practice that usually means a covered cutting station outdoors on a dry day, set up away from stacked boards, windows and doorways so dust does not settle on finished work or blow indoors.

• Support the board fully along its length while you cut. Cedral warns that the boards can break if they are handled carelessly on the flat.
• Do not cut boards that have been rained on or left out in the damp.
• After cutting, wipe dust off the board with a clean, dry cloth. Cedral's FAQ says to remove dust and dirt from cut planks immediately.

Treating cut edges

Cedral boards are coloured with a factory-applied paint finish, so a fresh cut shows the uncoloured fibre cement core. Here is what Cedral says:

• The Cedral FAQ highly recommends applying a thin coat of colour-matched touch-up paint along any trimmed edge.
• The fixing guide and maintenance guide say the touch-up paint is for cut edges and very small scratches only. It should be applied sparingly with a small, fine artist's brush, and any overspill onto the front face should be wiped off immediately with a clean, dry cloth.
• The maintenance guide explains that the factory finish leaves a slight sheen that touch-up paint cannot replicate on site. That is why the paint should not be used over larger areas of the face.
• For overlapping corners on Cedral Lap, where one board end is left on show, the fixing guide says those ends need to be decorated to match the Cedral finish.

Cedral touch-up paint is available in all 21 colours in 0.5 litre tins, priced at £25.14 ex VAT at the time of writing.

Drilling and fixing near the ends of a board

The Cedral fixing guide gives these rules:

• Screws: no pre-drilling is needed where the fixing is at least 50mm from the end of the board. Within 50mm of the end, pre-drill and countersink to suit the screw. Screws must be stainless steel, minimum 4.0 x 45mm.
• Hand nailing: no pre-drilling is needed at least 50mm from the end. Closer than 50mm, pre-drill with a 3mm bit. Normal HSS bits can be used, but they will need regular sharpening.
• Edge distance: keep fixings at least 20mm from the edges of the plank.
• Surface-mounted features: where items such as signs, gutters or canopies are fixed through the cladding, provide extra battens behind and drill clearance holes 3 to 5mm oversize through the Cedral. The boards must never carry additional structural loads.

Drilling creates the same kind of dust as cutting, so use the same controls. For fixings, see our stainless steel countersunk screws for Cedral Lap and the colour-head fibre cement screws, which are useful wherever a fixing stays visible. Everything else is in the Cedral Lap accessories and Cedral Click accessories collections.

Cutting mitred corners on Cedral Lap

If you are mitring external corners instead of using a corner trim, the fixing guide gives exact cut dimensions and a 44-degree undercut through the thickness of the board. It notes that the method only works on a true 90-degree corner. Follow the corner details in the Cedral fixing guide (PDF) and try a test piece first. Colour-matched aluminium corner trims avoid the need to mitre.

FAQs

What is the best blade for cutting fibre cement cladding?

Cedral recommends a diamond-dusted circular saw blade, specifically a 4-tooth, 180mm blade, for most cutting. Use a fibre cement jigsaw blade for shaped cuts and cut-outs.

Should I cut Cedral face up or face down?

Face down. Cedral advises cutting from the back with both a circular saw and a jigsaw, to protect the finished face.

Can I cut fibre cement indoors?

Cedral says cutting and drilling must take place in a dry, well-ventilated environment. Cutting outdoors under cover, with on-tool extraction and suitable RPE, is the sensible approach.

Do I need to paint the cut edges?

Cedral highly recommends a thin coat of colour-matched touch-up paint on any trimmed edge, applied sparingly with a fine brush.

Can I cut Cedral when it is wet?

No. Cedral says not to cut wet or damp boards, because the dust sticks to the surface and can stain it.

Ready to start?

If you are still choosing a colour, order free Cedral samples first. When you know your wall areas, use our Cedral quote form and we will price the boards, trims, fixings and tools for your project. You can also browse the full range on our Cedral cladding hub.