Practical Anchor Design – Key Checks for a Reliable Anchorage

Selecting an anchor is not simply a matter of choosing a product with a load value greater than the applied force. A reliable anchorage depends on the complete application, including the base material, concrete condition, loading, anchor geometry, edge distances, spacing, embedment depth and installation method.

For structural applications, these factors should be considered together before installation begins. A well-designed anchorage can also help avoid unnecessary complexity, oversized fixtures and additional installation work.

A practical approach to anchor design

The following steps provide a useful framework for assessing an anchoring application. For structural post-installed anchors in concrete, the final design should be verified using the applicable design requirements together with the performance data and conditions for the selected anchor.

1. Identify the base material

Start by determining exactly what material the anchor will be installed into. Concrete, solid masonry, hollow masonry, aerated concrete and panel materials behave differently and require anchoring systems designed for their characteristics.

For concrete applications, factors such as concrete strength, member thickness and whether the concrete is cracked or non-cracked can influence anchor performance.

Explore anchoring base materials >

2. Understand the applied loads

Determine the forces that the anchorage must resist. These may include tension, shear or a combination of both.

The application may also introduce bending or eccentric loading where the force acts away from the surface of the base material. Load direction and distribution can significantly influence both anchor selection and connection geometry.

Learn more about anchor loads >

3. Determine whether the concrete may be cracked

Structural concrete can develop cracks in areas subjected to tensile stress. An anchor installed in a region where cracking can occur must be suitable for those conditions where required.

If the concrete cannot reliably be considered non-cracked, the anchorage should be assessed for cracked concrete using an appropriate anchor system and design conditions.

Understand cracked and non-cracked concrete >

4. Select a suitable anchor type

Once the substrate and loading conditions are understood, suitable anchoring technologies can be considered.

Depending on the application, options may include:

• Mechanical expansion anchors
• Concrete screws
• Undercut or mechanically interlocking anchors
• Chemical or bonded anchoring systems
• Anchors designed for masonry or hollow substrates

The appropriate choice depends on more than load capacity alone. Installation requirements, concrete condition, available edge distances, spacing, environment and relevant product approvals should also be considered.

Explore the main types of anchors >

5. Check edge distance, spacing and embedment

The location of an anchor within the base material affects how loads are transferred into the surrounding concrete.

Important geometric parameters can include:

• Distance from the anchor to the concrete edge
• Spacing between neighbouring anchors
• Effective embedment depth
• Concrete-member thickness
• Anchor-group configuration

Reduced spacing or edge distances can reduce the available resistance because neighbouring anchors or concrete edges influence the same load-transfer zone.

There is no universal minimum spacing or edge distance that applies to every anchor. Product-specific values and the structural calculation should be used.

Explore anchoring conditions >

6. Determine the mounting method

The way the fixture is positioned and the anchor is installed also forms part of the design.

Common arrangements include:

• Pre-positioned fixing – the anchor is installed before the fixture is positioned
• Through fixing – the anchor passes through the fixture into the base material
• Stand-off fixing – the fixture is positioned away from the base-material surface

Stand-off arrangements in particular may introduce additional bending or eccentric forces and should be assessed accordingly.

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7. Check the product approval and technical documentation

For structural applications, a product should not be selected solely from a catalogue load value.

The relevant European Technical Assessment (ETA) provides important information about the conditions under which an anchoring system has been assessed.

Depending on the product, this can include:

• Approved base materials
• Concrete strength classes
• Cracked or non-cracked concrete
• Anchor dimensions and embedment depths
• Edge distances and spacing
• Loading conditions
• Installation requirements
• Fire or seismic performance where assessed

The scope of the approval should correspond with the actual application.

Learn more about ETA and DoP documentation >

8. Calculate the complete anchorage

For structural post-installed anchors in concrete, individual design parameters should not be checked in isolation.

The calculation needs to consider how the applied forces interact with the anchor system, concrete condition and connection geometry. Depending on the application, relevant checks can include steel resistance, pull-out, concrete failure, edge effects and interaction between tension and shear.

EN 1992-4 provides the European design framework for fastenings for use in concrete, used together with the product-specific performance data from the relevant ETA.

Anchor design at a glance

The cheapest anchor is not always the lowest-cost solution

Anchor unit price is only one part of the overall cost of an anchoring connection.

A product that appears less expensive may require larger edge distances, greater anchor spacing, additional fixing points or a different fixture design in order to satisfy the application requirements.

This can influence:

• The number of anchors required
• The size and thickness of the fixture or base plate
• Drilling and installation time
• Design complexity
• Material requirements
• Accessibility during installation

Conversely, an anchoring system with a higher individual product cost may enable a more compact or practical connection.

Anchor selection should therefore consider the complete fastening solution rather than comparing anchor prices in isolation.

Design efficiency and anchor geometry

A more suitable anchor does not necessarily mean a larger anchor.

Selecting an anchoring system whose assessed performance closely matches the application can sometimes allow a more efficient arrangement, for example through improved use of available edge distances, spacing or embedment conditions.

The objective is not to maximise anchor size but to identify a solution that satisfies the required performance within the actual connection geometry.

Common anchor design mistakes

Many anchoring problems begin before installation. Common design and selection mistakes include:

• Selecting an anchor from a single published load value
• Not checking whether concrete is cracked
• Ignoring shear or combined loading
• Assuming edge distance has no effect on resistance
• Positioning anchors too close together
• Not allowing sufficient embedment depth
• Ignoring concrete-member thickness
• Using an anchor outside the scope of its ETA
• Not accounting for fixture thickness
• Assuming suitability for cracked concrete also means seismic suitability
• Failing to consider installation and environmental conditions

Practical anchor design checklist

Before finalising a structural anchoring solution, check that you can answer the following questions:

• What is the base material?
• What is the concrete strength?
• Is the concrete cracked or non-cracked?
• What tension and shear loads are applied?
• Are there eccentric loads or bending effects?
• How many anchors form the connection?
• What edge distances are available?
• What spacing is available between anchors?
• What embedment depth can be achieved?
• Is the concrete member sufficiently thick?
• What is the fixture thickness?
• Which mounting method will be used?
• What environmental exposure will the anchor experience?
• Are fire or seismic requirements applicable?
• Does the anchor's ETA cover the intended application?
• Can the anchor be installed exactly as specified?

Calculate structural anchors with the Fabory Anchor Calculator

Manually assessing every interaction within a structural anchorage can become complex, particularly where several anchors, combined loading or restricted geometry are involved.

The Fabory Anchor Calculator helps you design post-installed anchors for structural use in concrete in accordance with EN 1992-4.

Enter the application parameters to evaluate suitable anchors based on the actual design conditions.

The calculator can help you:

• Assess tension and shear loading
• Calculate combined loading conditions
• Design for cracked and non-cracked concrete
• Consider anchor spacing and edge distances
• Evaluate different anchor configurations
• Assess fire and seismic conditions where applicable
• Identify why anchors do not satisfy the entered requirements
• Generate calculation reports for project documentation

Use the Fabory Anchor Calculator >

EN 1992-4 and practical anchor design

EN 1992-4 provides the European design framework for fastenings for use in concrete. It allows the behaviour of the complete anchorage to be assessed rather than relying on a single generic load value.

For post-installed anchors, the design is used together with the product-specific performance data and application conditions provided by the relevant ETA.

Depending on the anchorage, the design can account for factors including:

• Tension and shear loading
• Combined loads
• Anchor-group behaviour
• Concrete strength and condition
• Edge distance
• Anchor spacing
• Embedment depth
• Concrete-member geometry
• Relevant failure modes

This provides a more appropriate basis for structural anchor selection than relying on legacy generic design categories or simplified product comparisons.

From design to installation

A successful anchor calculation still depends on correct installation.

The anchor must be installed using the specified drill-hole diameter and depth, cleaning procedure, embedment, tightening or setting method and curing period where applicable.

Installation conditions should therefore be considered during design rather than only after the anchor has been selected.

Explore anchor installation and mounting methods >

Explore more anchoring guidance

Continue exploring Fabory's technical anchoring guidance:

• Types of anchors >
• Understanding anchor loads >
• Anchoring base materials >
• Cracked and non-cracked concrete >
• Anchoring conditions >
• Anchor installation and mounting methods >
• Explore all anchoring technical guidance >

Need help with an anchor design?

Structural anchoring applications can become complex where loads, connection geometry, concrete condition and installation constraints interact.

Fabory's technical specialists can help you assess the application requirements, identify suitable anchoring solutions and support the design process.

Contact our technical specialists >

Frequently asked questions about practical anchor design

Find answers to common questions about anchor selection, structural calculations and practical anchoring decisions.