Timber Bearing Check to EC5 - Cl 5.2.1.3

About this Timber Bearing Check to EC5 - Cl 5.2.1.3 Calculator

This calculator performs a timber bearing check at supports in accordance with Eurocode 5 Clause 5.2.1.3 (as referenced in the IStructE Manual to EC5). It checks that the design compressive stress perpendicular to the grain at a bearing location does not exceed the design bearing strength, accounting for material properties, load duration, service class, and support geometry.

• Structural engineer — verify bearing adequacy at timber beam supports quickly, with all modification factors and utilisation ratios calculated in one place.
• Timber frame designer — assess bearing stress for different support configurations, notch geometries, and strength classes without manual table lookups.
• Checking engineer — audit a bearing design with full traceability through each modification factor, material partial factor, and code clause reference.

This is an engineering-grade calculator hosted on CalcTree, where you can save it to a project, edit inputs live, and link it to other timber design checks in your workspace.

More info on Timber Bearing Check to EC5 - Cl 5.2.1.3

Inputs and material properties

The calculator takes timber strength class as a dropdown input and automatically retrieves the characteristic compressive strength perpendicular to the grain, bending strength, shear strength, and mean modulus of elasticity from the EN 338 property tables. The service class and material type are also selected by the user, and together these drive the partial material factor, modification factor for load duration and moisture, the deformation factor, the crack factor, and the notched beam factor. Beam geometry inputs include the cross-section depth and width, span, bearing length, and beam spacing, from which the cross-sectional area, section modulus, and second moment of area are derived directly.

Modification factors

Several modification factors are applied to reflect real-world conditions. The load duration factor accounts for the creep and strength reduction associated with sustained loading, selected from the standard duration classes. The system strength factor applies where multiple parallel members share load. The depth factor adjusts bending strength for sections shallower than the reference depth. The crack factor reduces effective shear area and is determined by material type. Where a notch is present at the support, the notched beam factor is calculated using the effective depth, notch slope length, and distance from the notch to the support, following the formulation in Clause 6.5.2. The bearing strength factor reflects the support configuration, distinguishing between continuous and discrete supports and solid or glulam softwood, as set out in Clause 6.1.5.

Design checks

The bearing check compares the design compressive stress perpendicular to the grain against the design bearing strength. The design stress is calculated from the applied design shear force divided by the effective bearing area, which is the product of the bearing length and beam width, multiplied by the number of beams per metre. The design bearing strength is derived from the characteristic compressive strength perpendicular to the grain, scaled by the load duration factor, the bearing strength factor, and divided by the partial material factor. A utilisation ratio is computed and a pass or fail result is returned automatically.

Code references

The calculation follows the IStructE Manual to EC5, with the bearing check at Clause 5.2.1.3. Material property tables reference EN 338, modification factors are drawn from EN 1995-1-1 Tables 2.1, 2.2, 3.1, and 3.2, and clause-specific checks cite Clauses 3.2, 6.1.5, 6.1.7, and 6.5.2. The partial material factor table follows the UK National Annex, Table NA.3, and the service class classification follows Clause 2.3.1.1 and Table NA.2.

Common Calculation Errors to Avoid

• Using the wrong service class — the service class directly controls the load duration factor and deformation factor; misclassifying an exposed or ventilated condition will give unconservative results.
• Ignoring notch geometry — if a notch is present at the support, failing to input the correct notch depth, slope length, and distance to the load significantly affects the notched beam factor and can make an unsafe design appear to pass.
• Applying an inappropriate bearing strength factor — the support configuration must be correctly identified; using the glulam softwood factor for solid timber, or a discrete support factor for a continuous bearing, will overstate the design resistance.
• Confusing factored and unfactored loads — the design shear force input must be the ULS design value, already factored; entering a characteristic or serviceability load will underestimate the demand.
• Overlooking beam spacing in the area calculation — the effective bearing area depends on the number of beams per metre of width; an incorrect spacing will directly scale the calculated stress up or down.
• Selecting an incorrect material type — the material type selection drives the partial factor, crack factor, and notch factor; for example, treating package-graded solid timber as individually grade-stamped gives a lower partial factor and non-conservative results.

FAQs

What does this calculation check and which clause does it follow?

This template checks whether a timber beam can resist the compressive stress perpendicular to the grain at its bearing points, such as at supports or point loads. It follows Eurocode 5 Clause 5.2.1.3 as outlined in the IStructE Manual for EC5, verifying that the design bearing stress does not exceed the modified design bearing strength.

What is k_c,90 and how do I choose the right support condition?

k_c,90 is a factor that increases the perpendicular-to-grain compressive strength to account for stress distribution beneath the bearing area. It ranges from 1.0 for general conditions up to 1.75 for discrete supports on glulam softwood where the applied load acts more than 2h away from the support. Select the condition that best matches your physical setup from the dropdown; using a higher value when not warranted is unconservative.

How does the notch depth affect the bearing and shear check?

When a notch is cut at the support, the effective depth h_eff is reduced, which feeds into the shear capacity reduction factor k_v via Clause 6.5.2. A deeper notch gives a smaller alpha ratio and a lower k_v, reducing the shear resistance at that location. If no notch is present, set the notch depth to zero and the template automatically sets k_v to 1.

What load should I enter for V_Ed?

Enter the design (factored) shear force at the support in kilonewtons. The template treats this as the bearing force F_c,90,d acting perpendicular to the grain over the bearing area defined by the bearing length l_b and the beam width b. The value should already include all relevant load factors per your load combination.

How do I set the correct service class and why does it matter?

Service class defines the moisture exposure conditions: class 1 is dry indoor use, class 2 is covered but potentially humid, and class 3 is exposed to weather. It directly controls k_mod and k_def values pulled from EC5 Tables 3.1 and 3.2. Using the wrong class can significantly overestimate the design strength, particularly for solid timber moving from class 2 to class 3.

Why is the material partial factor gamma_M set to 2.0 for package-graded solid timber?

EC5 Table NA.3 assigns a higher partial factor to solid timber graded by package rather than individually because there is greater uncertainty in the characteristic properties when individual pieces are not stamp-graded. If you are using individually graded timber, switch the material type accordingly to apply the lower gamma_M of 1.3 and avoid an overly conservative result.