How To Cut Composite Decking

Composite decking is an excellent option for decking projects in the UK. The durable, hardwearing material requires significantly less maintenance than natural wood and lasts much longer.

Installing decking is a relatively straightforward job for professionals or people with significant experience.

One important part of your composite decking project will be cutting boards to size. Not all boards will need to be cut, but the ones that do need to be cut precisely.

This guide will take you through everything you need to know about cutting composite decking.


Can You Cut Composite Decking?

The first thing that many people will ask is whether composite deck boards can be cut. In order for your decking material to fit the designated, some boards will need to be cut.

Cutting decking material should only be done with the correct tools, in a well-ventilated area, by experienced workers.


The Tools Needed to Cut Composite Decking

If you are carrying out composite decking installation, the following tools will be required for cutting the composite decking boards.

  • Chalk
  • Tape Measure
  • Speed Square
  • PPE
  • Mitre Saw
  • Circular Saw
  • Jigsaw
  • Table Saw


It is unlikely you would need all four saw types. The following section discusses these options and their benefits.


What Saw and Saw Blades Best for Cutting Composite Decking?

Deciding on which type of saw and saw blades to use when cutting composite decking is an important choice to make.

Carbide-tipped blades are a good option as they will stay sharp. Avoiding overheating is another important aspect of cutting composite decking, as it can affect the cut.

The number of teeth on a blade will also impact how quickly and accurately you can cut the composite boards.

A low tooth count on saw blades results in a rougher finish but allows you to cut more quickly.

A high tooth count on saw blades will provide a more accurate and fine cut, but it is significantly slower.

Cutting too slowly will allow the blade to heat up and can burn or melt the composite material.

Saw blades with a tooth count of 20 will typically suit a 6-inch saw blade. For a 7.25-inch saw blade, a 24-tooth count is more suitable, and a 40-tooth count saw blade is best for a 12-inch saw blade. We recommend a multipurpose aluminium 60+ tooth x 250mm saw blade.


Circular Saw

A Circular uses a rotary motion to spin the saw blade around an arbour. Circular saws are versatile power tools used professionally and in DIY projects.

The sharp saw blades are disc-shaped, and larger saw blades can be used for a deeper cut. The amount of teeth a circular saw blade has will affect the speed it can cut at.


Table Saw

Unlike circular saws, table saws are not mobile. The circular blade on a table saw is mounted on an arbour and will have an electric motor to drive it.

The blade comes through the table, and the composite board is then pushed into it for an accurate cut.

This differs from the circular saw that is controlled and pushed against the secured decking board.

The blade can be moved up and down to adjust the depth of the cut. You can also explore composite cutting table saw blades that are specially designed for cutting composite materials.


Miter Saw

A mitre saw, also spelt “miter saw” in some cases, is a saw that is mounted on a pivoting swing arm that allows the user to quickly and accurately cut at various angles.

Triple chip tooth mitre saw blades are available to produce a fine cut that won’t chip the delicate plastic veneer of a composite deck board.



A jigsaw is a much more accurate saw type that allows the user to cut curves and shapes.

A jigsaw is a great option for cutting composite decking that needs to go around shapes such as drain pipes.

Thin, flexible jigsaw blades are easier to cut curves with, and the teeth are measured in teeth per inch (TPI). A high TPI results in finer, smoother, and more accurate cuts.


How to Cut Composite Decking Boards

Now that you know all about the cutting tools needed to cut composite decking boards, you may want to know more about the cutting process.

It is important to mention that before you start cutting different materials, you must ensure your safety is a priority.

Always work in a well-ventilated area, and make sure you wear the necessary PPE. Your personal protective equipment should include a dust mask to minimise the risk of inhaling airborne particles.

Safety goggles should always be worn when using a saw to protect your eyes from chips or broken blades that can occur. Alternatively, a face shield can be used to give you additional protection.

Hearing protection is also recommended, as saws can be extremely loud. Gloves and loose-fitting clothing should be avoided when working with power tools to minimise the risk of it getting caught.


Composite Board Preparation

Preparing your boards to be cut is essential. Cleaning the boards and storing them in dry places out of direct sunlight is important.

Composite decking can be affected by thermal expansion, so cutting them when they are cool will allow you to get a more accurate cut.

You should then ensure the outer edges of the board are square. To do this, you should measure an eighth of an inch from the edge using a speed square. A chalk line should be drawn down the board length, and this area can be cut.



Accurately measuring the area where your decking installation will take place and taking into account the required gaps between boards and external walls is essential. Only then will you be able to measure your boards accurately.

Allowing additional length, so the board overhands the subframe, will allow you to cut and create a flush finish. It is always better to allow additional length at this point as this allows you to cut it down accurately. Cutting too short will result in a wasted deck board.


Straight Cut

Straight cuts are the most straightforward and are typical of square or rectangular decking areas.

Using chalk to mark where to cut clearly is advisable. This can then be cleaned off or removed for adjustments.


Angle Cut

Decks that feature diagonal sections or edges might seem like a daunting task, but this can be as straightforward as straight cuts with the correct planning and tools.

With the correct saw blades, using a mitre saw to cut at the required angle is simple.

Measuring the correct angles is an important part of this process and taking care to ensure your measurements are correct is vital.


Cutting Curved Boards

Curved boards can be cut in the same ways that straight and angled boards are.

The main difference is that the shape or curve of a board may require additional cuts to be made near the edges.



After cutting the boards, you will then have the task of installation to consider. Following the supplier’s directions is important, as deviating from these instructions can result in a warranty being voided.

Suppliers will provide explicit instructions on how their product should be installed, and the accessories that are also provided must be used to fit the boards.

Poor installation can limit the performance and lifespan of your composite decking, so you must have the experience to do this yourself or employ a reputable tradesperson.



Should I sand Composite decking after cutting it?

No, composite decking should never be sanded. Sanding composite decking can void the warranty. Only first generation composites can be lightly sanded.

Using saw blades with more teeth will result in smooth cuts that can be wiped down for a clean edge.


Should I seal the ends of composite boards after cutting?

You will be able to seal the ends of composite decking using lumber wax to prevent your deck boards from absorbing moisture.


Can I screw directly into composite decking?

You should not screw directly into composite decking; instead, you should use the hidden fasteners provided by the supplier.

Hidden fasteners are designed to securely hold the deck boards in place while allowing for the natural thermal expansion of the boards in hot weather.

Screwing directly into a composite board will pin it in place. As the board expands in the heat, it will put pressure around the screwed-in area and cause the board to warp.


How do I protect timber deck joists?

Your subframe is an essential part of your deck as it is designed to support the weight of the composite decking.

Ensuring your subframe is protected against the elements will give it a longer life. Using joist tape to cover exposed timber will protect it from moisture.

Joist tape is typically made of butyl or asphalt to protect it against rot or decay.


How do I choose a deck shape?

Choosing a deck shape will depend on the garden, the space available, and what you plan to use the area for.

A long narrow deck will be adequate for relaxing outside but might not be adequate for entertaining or garden parties.

You should consider the area you are interested in getting decked, and also look at how the sunlight comes into your garden to ensure you create a space that suits your needs.


Final Thoughts

If you plan to install composite decking in your garden, using a professional is a great way to ensure you get the finish you want.

If you have the necessary experience, composite decking boards should be relatively straightforward to install.

Cutting composite deck boards will typically be necessary, but using the right tools will also make this a straightforward task.

Your main priorities when cutting composite decking should be safety and accuracy.

Wearing the correct PPE and using power tools safely is an important part of any DIY work.

Taking the time to accurately measure the deck boards before cutting them should minimise the risk of mistakes.

Always try to leave a bit of additional length before checking. You will then be able to work on the board to get an accurate finish.

Taking the time to read the installation and warranty guidelines will help you to ensure the decking is safely installed and minimise the risk of voiding a warranty.

If you haven’t yet ordered your composite decking and are ready to after learning how to cut it to fit, give us a call or an email today.

Gary is the founder and CEO of Ecoscape UK. Gary graduated from Liverpool JM University in 2007 with a 2:1 in Economics. A passion for innovation, design and sustainability, Gary has put to market numerous wpc products/systems, some of which have UK and European registered designs. Outside of work Gary enjoys spending time with his family, the great outdoors and watching Manchester United.