Mechanical fixings are an important part of an EWI Pro external wall insulation system. Alongside the adhesive, they help secure the insulation boards back to the substrate and form part of what we describe as a dual-fix system.

So, how many fixings should you use?

Our 2026 Complete Guide recommends 5 mechanical fixings per 0.72m² insulation board, or approximately 7 fixings per m². This applies to both hammer and screw fixings within the standard coverage guidance.

That gives installers a useful starting point, but fixing selection is not just about quantity. The substrate, insulation type, fixing length and method of installation also need to be considered.

How Many EWI Fixings Are Needed Per Board?

The standard recommendation in our 2026 Complete Guide is:

5 mechanical fixings per 0.72m² board, or approximately 7 fixings per m².

The installation guide repeats the same recommendation when describing the mechanical fixing stage of an EWI installation: 5 fixings per board or 7 per m².

This makes 7 fixings per m² a useful figure when estimating how many fixings will be needed for a standard project.

However, the coverage section of the Complete Guide also makes clear that its material figures are based on factory guidelines and that actual requirements can vary according to site conditions.

So, the fixing allowance is a starting point for planning materials rather than a reason to ignore the requirements of the individual installation.

Why Do EWI Systems Need Mechanical Fixings?

EWI Pro external wall insulation systems use both adhesive and mechanical fixings.

The insulation is first bonded to the prepared substrate using the appropriate adhesive. Mechanical fixings are then installed to further anchor the insulation to the wall.

This dual-fix approach means the boards are not relying on one fixing method alone.

The mechanical fixing passes through the insulation and anchors into the substrate behind it.

That makes the condition and strength of the substrate particularly important.

Should You Carry Out Pull-Out Tests Before Installing EWI?

Yes. Our 2026 installation guidance recommends carrying out pull-out testing before commencing a project to help determine the correct fixing.

A Hydrajaw fixing tester, or equivalent, can be used to assess the strength of the substrate and establish whether it is suitable for supporting the solid wall insulation system.

The Complete Guide recommends testing the substrate in 15 locations per project, with additional tests potentially carried out on larger projects.

This is particularly useful because a fixing is only as effective as the substrate it anchors into.

Two walls may look similar from the outside but provide different fixing performance depending on their material, age and condition.

If installers are unfamiliar with pull-out testing, our Technical Team can also provide independent testing.

Does Every Substrate Require the Same Fixing?

No.

The purpose of the pull-out test is partly to help determine the correct fixing for the actual substrate being worked on.

The Complete Guide requires the wall to be assessed before installation. The substrate should be clean, dry and free from dust or other materials that could interfere with the system before the insulation is applied.

Pull-out testing then provides further information about the strength of that substrate and its suitability for the proposed mechanical fixing.

The fixing strategy should therefore be based on the actual building rather than simply repeating what was used on a previous project.

Which Fixings Are Used With EPS?

For EPS insulation, our 2026 Complete Guide identifies Plastic Pin Hammer Fixings as particularly suitable.

These fixings have an entirely plastic construction and are designed to be hammered through the insulation and into the substrate. Their plastic construction also helps minimise thermal bridging through the fixing.

EPS itself is installed as part of a dual-fix system using adhesive alongside mechanical fixings.

The correct fixing length will then depend partly on the thickness of the insulation being installed.

Which Fixings Are Used With Mineral Wool?

Mineral Wool requires a different approach.

The 2026 Complete Guide states that Rockwool external wall insulation boards require metal pin mechanical fixings as well as adhesive, with a minimum of 7 fixings per m².

The Mechanical Fixings section also identifies Metal Pin Hammer Fixings as suitable for supporting Mineral Wool insulation systems.

This is an important distinction for installers.

You should not assume that because a fixing is suitable for an EPS system, it is automatically the correct fixing for Mineral Wool.

The insulation system and relevant fixing type should always be considered together.

What About Screw Fixings?

EWI Pro also offers Metal Pin Screw Fixings.

Rather than being hammered into place, these are screwed into the substrate. The 2026 Complete Guide states that they are available in eight lengths to accommodate different insulation thicknesses.

Importantly, the guide also states:

Each Metal Pin Screw Fixing should anchor at least 35mm into the substrate.

That anchorage is separate from the thickness of the insulation itself.

For example, simply matching the fixing length to the board thickness would not provide the required anchorage into the wall.

How Long Should an EWI Fixing Be?

The 2026 Complete Guide provides a straightforward rule for standard fixing length:

The fixing should typically be 40mm longer than the thickness of the insulation.

For example, if the system uses thicker insulation, the fixing length will also need to increase.

There is an important exception in the guide for pebbledash substrates.

Where insulation is being fixed onto pebbledash, the Complete Guide states that the fixing should be 65mm longer than the insulation thickness.

So the general guidance is:

• standard substrate: insulation thickness + 40mm
• pebbledash: insulation thickness + 65mm

For Metal Pin Screw Fixings, the additional requirement of at least 35mm anchorage into the substrate should also be observed.

When Should Mechanical Fixings Be Installed?

Mechanical fixings should not be installed immediately after the insulation boards have been bonded to the wall.

According to the 2026 Complete Guide, the holes for the fixings should be drilled at least two or three days after the insulation boards have been attached to the substrate with adhesive.

The fixings are installed before the reinforcing fibreglass mesh layer is added.

This allows the adhesive behind the insulation sufficient time to set before the additional mechanical fixing stage begins.

The installation sequence therefore follows:

Adhesive → Insulation Boards → Allow to Set → Mechanical Fixings → Reinforcement Layer

How Should EWI Fixings Be Installed?

Depending on the fixing being used, the fixings may either be:

• hammered into place; or
• screwed into the substrate using a power tool.

The 2026 Complete Guide shows two recommended fixing patterns alongside its installation instructions and recommends 5 fixings per board or 7 per m².

Installers should therefore follow the appropriate fixing layout rather than positioning fixings randomly across the insulation.

Correct positioning helps create a consistent and secure fixing arrangement across the façade.

Are Additional Fixings Ever Used?

Yes, depending on the system and detail.

For example, the Complete Guide’s steel-frame Mineral Wool installation shows each 1200 x 600mm slab fixed using a domino pattern of 5 fixings per slab.

It then specifically states that additional fixings are used around windows to reinforce these areas.

This example is specific to that installation detail, but it demonstrates an important point: the standard fixing allowance does not mean every area of every system is necessarily treated identically.

Installers should follow the fixing arrangement shown for the system and project they are working on.

What About Fixings and Thermal Bridging?

Mechanical fixings pass through the insulation layer, so reducing their thermal effect is also considered within the system.

The 2026 Complete Guide explains that both Metal Pin Hammer Fixings and Plastic Pin Hammer Fixings are designed to help minimise thermal bridging.

Where Metal Pin Mechanical Fixings are used with EPS, the installation guide also recommends using EPS dowel capsto minimise thermal bridging.

The dowel caps are fixed in place using EWI-240 EPS Foam Adhesive.

Once the system is complete, the fixing positions should not remain visible through the finished façade.

What About Firebreak Fixings?

Firebreaks require their own appropriate mechanical fixing.

The 2026 Complete Guide identifies Metal Lamella Firebreak Fixings for use with firebreaks.

These fixings are made from steel and are designed for use with Mineral Wool firebreaks where a suitable metal mechanical fixing is required.

Again, this shows why it is important to select the fixing according to its role within the system rather than assuming that one fixing type can be used throughout every part of an EWI installation.

How Many EWI Fixings Should You Order?

For standard material estimating, the 2026 Complete Guide uses:

7 fixings per m² or 5 fixings per 0.72m² board.

Both EWI Pro Hammer Fixings and Screw Fixings are supplied in boxes of 200, according to the same coverage table.

This gives installers a straightforward basis for calculating the approximate quantity required from the total wall area.

However, site conditions and system details should still be checked before finalising the order.

What Should Installers Remember About EWI Fixings?

There is more to mechanical fixing than remembering “7 per m².”

The main points from our 2026 Complete Guide are:

• use 5 fixings per 0.72m² board or approximately 7 per m² as the standard recommendation
• carry out pull-out testing before starting the project to help determine the correct fixing
• the guide recommends testing in 15 locations per project, with more tests considered on larger projects
• Plastic Pin Hammer Fixings are particularly suitable for EPS
• Metal Pin Hammer Fixings are suitable for Mineral Wool
• Mineral Wool requires a minimum of 7 fixings per m²
• Metal Pin Screw Fixings should achieve at least 35mm anchorage into the substrate
• fixings should typically be 40mm longer than the insulation thickness
• where fixing through pebbledash, this increases to 65mm longer than the insulation thickness
• mechanical fixing should take place after the insulation has been bonded to the wall, with the guide advising at least two to three days before drilling
• some system details may require additional fixings, such as around windows in the steel-frame Mineral Wool installation.

The key point is that quantity, fixing type, length and substrate all need to be considered together.

For installers, establishing the correct fixing starts before the boards go onto the wall. Check the substrate, carry out the appropriate testing and follow the fixing guidance for the EWI system being installed.

For further information, refer to the EWI Pro Complete Guide 2026 Edition or speak to our Technical Team for support with pull-out testing, system guidance and project-specific technical requirements.

External Wall Insulation Fixings FAQs

How many fixings do you need per EWI board?

The EWI Pro Complete Guide 2026 recommends 5 mechanical fixings per 0.72m² insulation board, equivalent to approximately 7 fixings per m².

How many EWI fixings are needed per square metre?

The standard EWI Pro recommendation is 7 fixings per m². Mineral Wool also has a stated minimum of 7 fixings per m² within the 2026 Complete Guide.

How long should external wall insulation fixings be?

Typically, the fixing should be 40mm longer than the insulation thickness. For insulation installed over pebbledash, the guide states that the fixing should be 65mm longer than the insulation thickness.

How far should EWI screw fixings enter the substrate?

The 2026 Complete Guide states that Metal Pin Screw Fixings should anchor at least 35mm into the substrate.

Do you need pull-out tests before installing EWI?

The Complete Guide recommends carrying out pull-out testing before commencing a project to help determine the correct fixing and assess the strength of the substrate. It recommends testing at 15 locations per project, with additional testing considered on larger projects.

What fixings should be used for EPS insulation?

The EWI Pro Complete Guide identifies Plastic Pin Hammer Fixings as particularly suitable for securing EPS insulation boards to the substrate.

What fixings should be used for Mineral Wool?

The guide identifies Metal Pin Hammer Fixings as suitable for EWI Pro Mineral Wool systems and states that Rockwool external wall insulation requires metal pin mechanical fixings alongside adhesive.

Need help with fixing requirements for your project?

Speak to our Technical Team for support with pull-out testing, fixing selection and EWI system guidance