Single-span beam calculator
Calculate timber beam capacity and checks according to DIN EN 1995
Loads
Permanent build-up and self-weight
Use-related action on the supported area
Regional roof snow action where relevant
Used to derive the governing timber modification factor.
Geometry
Typical spacing for the tributary strip carried by one beam.
Clear span between the two supports.
Width mainly influences shear and bearing reserve.
Height usually has the strongest effect on bending and deflection.
Material and limits
Defines timber strength and stiffness for the check.
Describes the usual moisture exposure in service.
Standard serviceability limit is often checked around L/300 for common timber work.
Single-span beams for first sizing
Think of a timber beam that sits on two supports, for example two walls or a wall and a post line. That is a single-span beam: one member, two support points, one clear span in between.
It is the simplest beam model in timber design, but it still has to carry load safely. A roof beam, floor joist, terrace beam, or small girder may all look simple on site. The check behind them is still about load path, strength, and serviceability.
Quick walkthrough
What a single-span beam is
A single-span beam works like a small bridge. It spans one gap and transfers distributed load into two supports.
That simple support condition matters because it controls the internal forces. For this beam type, the critical bending moment is in the middle of the span, while the highest shear force is near the supports.
Where you see this beam model
- Floor joists: timber members that span from one wall to another and carry your floor build-up.
- Roof beams: members that span between walls or posts below purlins or a roof deck.
- Terrace beams: beams below decking that carry one tributary strip.
- Balcony or canopy members: beams that transfer roof or platform load into supports.
- Shelves and small timber details: even a shelf board between two brackets follows the same basic idea.
Core terms you should know
Span
The span is the distance between the two supports. If your beam sits between two walls that are 5 m apart, the beam span is 5 m.
Load
Load is everything that acts on the beam. In this tool, the main inputs are area loads in kN/m2, which are converted into a line load for one beam using the spacing.
Deflection
Every beam bends under load. Too much deflection can lead to cracked finishes, noisy floors, or a soft feel underfoot even when the beam still passes the strength check.
Timber strength class
Not all timber has the same strength and stiffness. A class such as C24 gives you a known engineering baseline. Higher classes can carry more stress, but section depth is still often the strongest sizing lever.
Beam section
The section is the beam width and height. Both matter, but height usually matters more for bending and deflection.
How to use this calculator
Use this tool for a first pass. Enter realistic loads, define the span and section, choose the material, then read the governing checks.
Step 1: Enter the loads
- Dead load: self-weight and permanent build-up such as sheathing, insulation, lining, and finishes.
- Live load: use-related load from people, furniture, storage, or access.
- Snow load: relevant when the member supports roof area exposed to snow.
- Beam spacing: the distance to the next beam, which defines how much area one beam carries.
Step 2: Define system and geometry
- Span: clear distance between supports.
- Beam width and height: the section you want to test.
Step 3: Choose the material
Select the timber class and the service class. If you are comparing common softwood sections for interior work, C24 in service class 1 is often the starting point.
Step 4: Read the result
The tool checks bending, shear, and deflection. Read all three. One beam can pass bending and still fail deflection.
- Green: clear reserve.
- Yellow: close to the limit, workable but with little margin.
- Red: section too weak, too small, or too long for the input load case.
Where to get the input values
- Span: measure it on site or from the drawing.
- Timber class: check the supplier mark or product documentation.
- Loads: use build-up data, standards, manufacturer values, or project notes from the engineer.
- Snow load: use the value that applies to your region and elevation.
Full timber workflow: from roof beam to foundation
A beam is rarely a stand-alone problem. In a real timber project, one check leads into the next.
Example: carport workflow
- Single-span beam calculator
Use this step to size the roof beams or purlins and to read the governing bending, shear, and deflection checks. - Post calculator
Use the next step to check the vertical timber posts for compression and buckling under the beam reactions. - Foundation calculator
Use the final step to size the concrete footing from soil capacity and post load.
Practical rule: start with the beam, because the beam load usually defines the support reactions for the next checks.
Important limit
This calculator gives you a fast pre-sizing result. It does not replace a structural engineer or a project-specific verification.
For any construction decision with structural relevance, you still need a qualified review. The tool uses simplified assumptions and cannot cover every support condition, detailing case, execution issue, or legal requirement.