External Wall Insulation Fixings: Complete Guide

By master
May 15, 2025

Want to ensure your external insulation system stands the test of time? The secret lies in proper fixings! In this comprehensive guide, Penguins BM experts explain everything you need to know about external wall insulation fixings - from selecting the right types to professional installation techniques.

Are you planning an external wall insulation project? The quality of your external wall insulation fixings can make the difference between a long-lasting installation and one that fails prematurely. This comprehensive guide covers everything you need to know about choosing and installing the right fixings for your project.

What Are External Wall Insulation Fixings?

External wall insulation fixings are specialised mechanical fasteners designed to securely attach insulation boards to exterior walls. These critical components of any external wall insulation system provide the necessary support to keep insulation boards firmly in place, even under challenging weather conditions.

The fixings work alongside adhesive to create a dual-fixing mechanism. While the adhesive provides overall surface bonding, the mechanical fixings ensure the system remains secure if adhesive bonds weaken over time or in adverse conditions. This dual approach is essential for long-term performance of your insulation system.

Types of External Wall Insulation Fixings

There are several types of fixings available for different insulation materials and substrates:

1. Plastic Insulation Plugs with Metal Pins

Our plugs for polystyrene metal pin are the most common type of fixing used for securing polystyrene insulation boards. These consist of a plastic expansion plug with a metal pin that drives through the centre. When installed:

The plastic plug expands in the drilled hole, creating a secure grip
The metal pin provides reinforcement and prevents plug collapse
The large disc-shaped head distributes pressure evenly across the insulation surface

These fixings are ideal for concrete, brick, or blockwork substrates and provide excellent pull-out resistance.

2. Spiral Anchors

Spiral Anchors are specialised fixings designed for lightweight insulation materials. Available in different lengths (such as our 50mm and 85mm options), these twist-in fixings:

Require no pre-drilling in many substrates
Provide excellent holding power with minimal thermal bridging
Are particularly suitable for softer insulation materials

Our spiral anchors come in various sizes, including Spiral Anchor 50 x 28 and Spiral Anchor 85 x 28 mm, accommodating different insulation thicknesses.

3. Pressure Plates

Pressure plates are used in conjunction with other fixings to increase the surface area of the fixing head, spreading the load more evenly across the insulation. These are particularly valuable:

When installing in areas with high wind loads
For thicker insulation boards
Around edges and corners where additional support is needed

4. Insulation Caps and Discs

Polystyrene discs serve as caps for insulation fixings, helping to:

Reduce thermal bridging through the fixings
Create a smooth surface for rendering
Prevent moisture ingress around fixing points

How to Attach External Wall Insulation?

Proper installation of external wall insulation requires careful attention to detail, especially when it comes to fixings:

Step 1: Prepare the Surface

Before attaching any insulation:

Ensure the wall surface is sound, clean and free from loose material
Remove any existing paint or render that could compromise adhesion
Apply appropriate primer if necessary, such as our Totalgrunt Primer

Step 2: Apply Adhesive

Use a suitable adhesive mortar to bond the insulation boards to the wall
Apply adhesive using either the “dot and dab” method or full-surface application
Ensure at least 40% of the board surface has adhesive contact with the wall

Step 3: Position the Insulation Boards

Place the boards horizontally with staggered vertical joints
Ensure boards are tightly butted together
Allow the adhesive to partially set (typically 24-48 hours)

Step 4: Install Mechanical Fixings

This is where your external wall insulation fixings come into play:

Mark fixing positions – typically 5-7 fixings per square metre, with more around edges
Drill through the insulation into the substrate to the required depth
Insert the appropriate fixing, such as our Plugs for polystyrene
Drive the pin in fully so the fixing head sits flush with or slightly below the insulation surface
Apply insulation caps over the fixings if required

Step 5: Apply Reinforcement Layer

After securing the insulation with fixings, it’s essential to apply a high-quality reinforcement mesh to prevent cracking and ensure system durability:

Premium Fibreglass Mesh Reinforcement

Our bestselling reinforcement mesh provides excellent strength and durability for all external wall insulation systems. Designed to prevent cracking and ensure long-lasting results.

High tensile strength
Alkali resistant
Easy application
Professional grade quality

£45.83 ex. VAT

View Product

To properly apply the reinforcement layer:

Allow to dry completely before proceeding to the final render coat
Apply base coat render evenly across the insulation surface
Embed our high-quality fiberglass mesh into the wet base coat
Ensure mesh overlaps by at least 100mm at all joints
Apply a second thin layer of base coat to fully cover the mesh

Step 6: Finish with Render

Complete the system with an appropriate render from our range of render products.

Can You Screw Into External Wall Insulation?

This is a common question we receive at Penguins BM. The short answer is: you should never screw directly into external wall insulation after installation.

Standard screws will not provide adequate support and will damage the integrity of the insulation system. Instead:

For lightweight items (below 5kg): Use specialised adhesive anchors designed for EWI systems
For heavier items (above 5kg): Use extension fixings that penetrate through the insulation into the structural wall behind
For very heavy items: Plan attachment points before insulation is installed and use stand-off brackets

Always consult a professional when attaching objects to external wall insulation, as improper fixings can compromise the weather resistance and thermal performance of the entire system.

What Are Insulation Fixings?

Insulation fixings are specially designed mechanical fasteners that secure insulation materials to various substrates. Unlike standard screws or nails, these fixings:

Have wider heads to spread the load across soft insulation materials
Are designed to minimize thermal bridging
Incorporate features to prevent moisture ingress
Provide reliable long-term support even with temperature fluctuations

Our range includes specialized options like Plugs for polystyrene and Spiral Anchors to suit different installation requirements.

What is the Cheapest Way to Insulate External Walls?

When considering cost-effective external wall insulation, it’s important to balance initial costs with long-term performance:

Standard EPS (Expanded Polystyrene)

Standard white EPS represents the most economical insulation material for external walls. When combined with appropriate fixings from our range, it provides:

Graphite Polystyrene Facade Boards

Our high-quality graphite-enhanced polystyrene boards offer superior thermal performance compared to standard white EPS, while remaining cost-effective for external wall insulation projects.

Enhanced thermal insulation
Lightweight and easy to install
Compatible with all our fixing systems
Available in multiple thicknesses

From £3.33 ex. VAT

View Product

Optimising Fixing Costs

To keep costs down while maintaining quality:

Use the correct number of fixings – not too many, not too few
Choose the right length – longer fixings cost more but are necessary for thicker insulation
Consider our Plugs for polystyrene for an optimal balance of cost and performance

False Economy Warnings

Beware of these false economies:

Using too few fixings can lead to system failure and costly repairs
Choosing inferior quality fixings may require replacement after a few years
Skipping insulation caps allows thermal bridging, reducing energy efficiency

Remember: the cheapest option initially isn’t always the most cost-effective long-term solution.

Choosing the Right External Wall Insulation Fixings for Different Substrates

The substrate material significantly impacts which fixings will perform best:

Concrete and Solid Brick

For solid, dense substrates:

Our Plugs for polystyrene provide excellent pull-out strength
Drilling should be done with a hammer drill
Recommended embedment depth: 25-35mm into the substrate

Hollow Brick and Blockwork

For hollow or perforated materials:

Longer versions of our metal pin fixings are recommended
The fixing needs to penetrate through voids to engage the material properly
Consider additional fixings to ensure adequate support

Aerated Concrete Blocks (Ytong, Hebel)

For lightweight aerated concrete:

Special fixings with coarser threads provide better grip
Pre-drilling should be done without hammer action
Our Spiral Anchors may provide superior hold in some cases

Timber Frame Construction

For wooden substrates:

Screw-in fixings perform better than hammer-in types
Ensure fixings penetrate into structural timbers, not just sheathing
Corrosion-resistant finishes are essential

Common Mistakes When Installing External Wall Insulation Fixings

Avoid these common errors when installing external wall insulation:

1. Insufficient Fixing Depth

Fixings must penetrate the substrate by the manufacturer’s specified depth (typically 25-35mm). Inadequate penetration severely compromises pull-out strength.

2. Incorrect Fixing Pattern

The standard fixing pattern should follow a W-shape on each board, with additional fixings at corners and edges. Irregular patterns can lead to uneven stress distribution.

3. Using Damaged Drill Bits

Worn or incorrectly sized drill bits create holes that are too large or too small, compromising the fixing’s grip. Always use sharp bits of the correct diameter.

4. Ignoring Edge Distances

Fixings placed too close to the edge of insulation boards or too close to the edge of building elements may not provide adequate support.

5. Overtightening Fixings

Driving fixings too deep can compress and damage the insulation. The fixing head should sit flush with the insulation surface or slightly recessed.

Professional Tips for External Wall Insulation Installation

Our Penguins BM experts recommend these professional tips:

1. Use the Right Tools

Invest in or rent a good quality hammer drill with depth stop for consistent drilling. Our Plastering tools section offers essential equipment for professional installation.

2. Consider Wind Zones

For buildings in exposed locations or at higher elevations, increase the number of fixings per square meter, particularly around edges and corners where wind forces are strongest.

3. Check Pull-Out Tests

For uncertain substrates, perform on-site pull-out tests to confirm the suitability of your chosen fixings before proceeding with the full installation.

4. Manage Thermal Bridging

Use insulation caps over metal fixings to reduce thermal bridging and prevent “fixing ghosting” (cold spots visible on the finished facade).

5. Consider Seasonal Timing

Install fixings when temperatures are above 5°C to ensure proper expansion of plastic components. Extremely hot weather can also impact installation quality.

Conclusion

Choosing the right external wall insulation fixings is essential for the long-term performance of your insulation system. At Penguins BM, we offer a comprehensive range of high-quality fixings suitable for various substrates and insulation types.

Remember that proper installation is just as important as product selection. Follow manufacturer guidelines, consider the specific requirements of your project, and don’t compromise on fixing quality or quantity.

For more information about our products or for expert advice on your next external wall insulation project, contact our team today.

Related Articles Explore more of our expert guides to external wall insulation:

Visit our Blog for more valuable insights and expert advice on external wall insulation and other building materials.

This article was prepared by industry experts with extensive experience in external wall insulation systems and materials. The information provided is based on current best practices and manufacturer recommendations as of May 2025.