Load Bearing Wall Beam Calculator

Clear span L (m)

Uniform load w (kN/m)

Unfactored line load from wall, floor and roof reactions.

Midspan point load P (kN)

Optional concentrated load; use zero if not applicable.

Beam width per ply b (mm)

Enter width for one member; plies are handled below.

Number of plies

Parallel members bolted together are treated as one built-up beam.

Beam depth h (mm)

Allowable bending stress Fb (MPa)

Obtain from design tables for actual material grade.

Allowable shear stress Fv (MPa)

Modulus of elasticity E (MPa)

Typical timber may be 8000–12000 MPa; check design values.

Beam density γ (kN/m³)

Approximate: timber ~5, concrete ~24, steel ~78.5.

Load factor on w and P

Use 1.0 for service combinations; higher for ultimate checks.

Include beam self weight in uniform load

When checked, self weight is added before load factors.

Deflection limit (L / ?)

Common limits are L/240, L/360, or more stringent.

Calculate Beam Checks

Download CSV Download PDF

This tool is for preliminary checks only; always consult a qualified structural engineer before altering load bearing walls.

The table below shows typical example values for a timber beam supporting a load bearing wall. Always verify loads and material properties from reliable design references.

1. Typical applications of this calculator

This tool is most often used when planning new openings in internal or external load bearing walls, resizing existing lintels, or checking temporary support beams during renovation works.

2. Choosing realistic load inputs

Accurate results depend on realistic load estimates. Use building code tables, engineering reports or manufacturer data to determine wall weight, roof and floor loads instead of guessing approximate values.

3. Understanding utilisation ratios

Utilisation ratios near or above one indicate the trial beam is overstressed. Aim for bending, shear and deflection ratios well below one to allow for modelling uncertainties and construction tolerances in real projects.

4. Limits of the simplified beam model

The calculator assumes a straight prismatic beam with simple supports and loads in one plane only. It does not cover complex framing, torsion, multi-span beams or partial lateral restraint, which must be analysed using more advanced structural methods.

Designing a beam for a load bearing wall involves combining realistic loading assumptions, material properties and simple structural formulas to check bending, shear and deflection limits.

1. Determine the span and support conditions. Measure the clear distance between the supporting points. This calculator assumes a simply supported beam with no cantilevers.
2. Calculate line loads from the wall and supported areas. Convert tributary roof and floor loads plus wall self weight into an equivalent uniform load in kN/m.
3. Add concentrated loads where required. Include point loads for items such as posts, chimneys, heavy tanks or concentrated reactions.
4. Select a trial beam size and material. Choose a practical width, depth and number of plies based on available timber, LVL or steel sections and construction constraints.
5. Obtain design strengths and stiffness. Take allowable bending and shear stresses plus modulus of elasticity from relevant standards or manufacturer literature.
6. Apply safety or load factors. Multiply characteristic loads by suitable factors for serviceability or ultimate combinations as required by the governing design code.
7. Check bending, shear and deflection. Compute maximum bending moment, shear force and midspan deflection using beam formulas and compare utilisation ratios against allowable limits.
8. Refine the section if limits are exceeded. Increase depth, width, number of plies or change material grade until bending, shear and deflection ratios fall comfortably below unity.
9. Document and seek professional review. Record assumptions, input values and results and have the final design checked and stamped by a qualified structural engineer.

When a load bearing wall is carried by a single steel beam, concentrated reactions from floors or secondary beams often govern the design more than the uniform wall load.

1. Identify critical point loads. Determine reactions from supported beams, joists or columns that deliver concentrated forces onto the steel member at known positions.
2. Combine point loads with distributed wall weight. Convert the wall and any continuous line loading into kN/m and superimpose with the discrete point loads for the full span.
3. Select a trial steel section family. Decide whether you will use rolled I-beams, channels or built-up plate girders and select a preliminary depth based on span-to-depth rules of thumb.
4. Calculate maximum bending moment and shear. For a simply supported beam with a central point load, check that the calculator’s moment and shear values reasonably match code-based design examples.
5. Compare required section modulus to catalogue values. Compute \( S_{\text{req}} = M_{\text{max}} / F_b \) and select a standard steel profile with section modulus and shear capacity exceeding these demands with comfortable reserve.
6. Check serviceability and lateral stability. Verify that deflection under service loads satisfies span ratio limits and ensure the steel beam has adequate lateral restraint to prevent buckling.
7. Verify bearing and connection details. Confirm that end supports provide sufficient bearing length and design plates, angles or end plates for safe transfer of point loads into the beam.
8. Adjust the beam size or grade if utilisation is high. Increase the section depth, choose a heavier designation or move to a higher steel grade until both strength and deflection checks are satisfactory.
9. Document the final steel beam selection. Record profile designation, grade, span, loads and utilisation ratios and submit calculations to a structural engineer for independent verification.

The calculator assumes a simply supported prismatic beam with a uniform distributed load along the full span and an optional single point load applied at midspan.

• Uniform load bending moment: \( M_w = \dfrac{w L^2}{8} \)
• Point load bending moment (midspan): \( M_p = \dfrac{P L}{4} \)
• Total maximum bending moment: \( M_{\text{max}} = M_w + M_p \)
• Uniform load shear at supports: \( V_w = \dfrac{w L}{2} \)
• Point load shear at supports: \( V_p = \dfrac{P}{2} \)
• Total maximum shear: \( V_{\text{max}} = V_w + V_p \)
• Rectangular section properties:
  Section modulus \( S = \dfrac{b h^2}{6} \),
  second moment of area \( I = \dfrac{b h^3}{12} \),
  area \( A = b h \).
• Built-up beams: for \( n \) identical plies in parallel, effective width \( b_{\text{eff}} = n b \).
• Beam self weight: when enabled, additional uniform load \( w_{\text{self}} = \gamma\, b_{\text{eff}} h \), with \( \gamma \) in kN/m³ and dimensions in metres.
• Factored design loads: \( w_d = \phi (w + w_{\text{self}}) \), \( P_d = \phi P \), where \( \phi \) is the load factor.
• Bending check: design bending stress \( \sigma = \dfrac{M_{\text{max}}}{S} \leq F_b \)
• Shear check (approximate): maximum shear stress \( \tau \approx \dfrac{1.5 V_{\text{max}}}{A} \leq F_v \)
• Deflection due to uniform load: \( \delta_w = \dfrac{5 w_d L^4}{384 E I} \)
• Deflection due to midspan point load: \( \delta_p = \dfrac{P_d L^3}{48 E I} \)
• Total midspan deflection: \( \delta = \delta_w + \delta_p \leq \dfrac{L}{\text{ratio}} \)
• Required section modulus: \( S_{\text{req}} = \dfrac{M_{\text{max}}}{F_b} \)
• Required depth for chosen ply width: from \( S_{\text{req}} = \dfrac{b h^2}{6} \Rightarrow h_{\text{req}} = \sqrt{\dfrac{6 S_{\text{req}}}{b}} \)

All formulas are expressed in consistent metric units (N and mm). Always verify assumptions, design factors and units when adapting this tool.

1. Define the span. Measure the clear distance between supports and enter the value in metres.
2. Estimate the basic loading. Determine unfactored vertical line load carried by the beam per metre, including wall self-weight, floor and roof reactions.
3. Add any point loads. If a heavy element such as a column, chimney or concentrated reaction bears near midspan, enter its characteristic value as a point load.
4. Select beam size and plies. Input the width of one member, number of plies and overall depth, matching available timber, LVL or steel sizes.
5. Enter material properties. Provide allowable bending and shear stresses plus modulus of elasticity from manufacturer data or applicable design standards.
6. Control self weight and factors. Choose whether to include beam self weight using an appropriate density, then set a load factor for serviceability or ultimate combinations.
7. Choose the deflection limit. Common values are L/240 for general use or L/360 for more sensitive finishes such as brittle partitions or glazing.
8. Run the calculation. Press the calculate button and review utilisation ratios for bending, shear and deflection, together with effective factored loads and suggested minimum depth.
9. Export your results. Use the CSV button to download tabular output or the PDF button to print or save a formatted calculation sheet for documentation.
10. Confirm with an engineer. Treat the outcome as a screening check only; final design and reinforcement details must be confirmed by a qualified structural engineer.