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CanadaCSA O86:19NBCC 2015CWC Wood Design Manual 2017

Wood Beam

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The easy to use online Calcs.com Wood Beam Calculator to CSA O86:19 enables you to do quick and powerful design and analysis for simple and continuous timber beams, with unlimited supports and loads. Choose from our library of thousands of common wood sections, or create your own and get instant results with our easy to understand traffic light checks for moment, deflection, and shear.
The Calcs.com Wood Beam - Generic Beam, Joist, and Girder Calculators allow you to quickly design wood horizontal members. In this article, each section of the calculator will be explained followed by a worked example. The Wood Beam Calculator has 4 main sections
  1. Key Properties
  2. Loads
  3. Design Conditions
  4. Summary and Graphs

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Worked example

Design a wood beam with the following characteristics:

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* Length: 4 meters

  • Member type: Glulam, Douglas Fir
  • Supports: Pinned and roller support on the left and right respectively, 75 mm bearing length
  • Bracing: No continuous bracing
  • Loads: 10 kN/m dead load and 15 kN/m live loads along the strong axis
  • Self-weight included
  • Dry service conditions, untreated with no load sharing

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Key Properties Input

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Load Input

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Design Conditions Input

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Summary and Graphs

Based on the summary and graphs, you can see that a 7x13.5 [175x342] 24f-E Douglas Fir glulam beam is suitable for this design scenario based on the governing 1.25D + 1.5(L+Lr) load combination. Looking at the load capacity percentages, a different beam may be suggested as the factored bearing and shear capacities are relatively high.
Access the full PDF file here: [CA] Wood Beam Example

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Method & scope

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See the exact clause

Every check in this calculator links back to its governing clause in CSA O86. Open the Formula Reference panel on any result and select the clause reference to read it. See Viewing Clauses from Inside a Calculator.

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Calculation method

Structural model and load combinations
The calculator models the beam as a one-dimensional element and computes bending moment, shear, and deflection diagrams under each NBCC 2015 load combination. Loads are entered by type, dead (D), live (L), snow (S), wind (W), and the calculator automatically generates all governing strength (ULS) and serviceability (SLS) combinations, for example:
  • 1.25D + 1.5L
  • 1.25D + 1.5S + 1.0L
  • 0.9D + 1.5W (uplift check)
Three independent sets of serviceability combinations are generated for short-term (live/snow), long-term (including creep), and simplified DL+LL deflection checks.
Bending moment resistance (CSA O86:19 Cl.7)
Factored bending resistance M_r is computed from the reference bending strength F_b adjusted by a chain of CSA O86:19 factors:
  • K_H, system factor for repetitive-member assemblies
  • K_Scs, service-condition factor for bending
  • K_T, treatment factor
  • K_zbg, size factor for sawn lumber, or volume factor for glulam members
Lateral stability is checked by computing the slenderness ratio C_B = L_e × d / b² for each unbraced segment. Where C_B exceeds the threshold for full resistance, the lateral stability factor K_L is applied. The slenderness ratio must remain at or below 50 per CSA O86:19 Cl.7.5.6.4, the calculator flags a failure if this limit is exceeded. moment utilization = M_f / M_r ≤ 1.0
Shear resistance (CSA O86:19 Cl.6.5.4.3)
Factored shear resistance V_r applies the service-condition, treatment, and size adjustment factors to the reference shear strength F_v. For glulam members the calculator uses the CSA O86 simplified shear strength method, which is valid for members with volume under 2 m³. Shear demand is taken at the location of peak shear, which may conservatively be directly over the support rather than at distance d. shear utilization = V_f / V_r ≤ 1.0
Bearing capacity
For each support, factored bearing demand Q_f is checked against factored bearing resistance Q_r, adjusted for service condition and treatment. A bearing contact area is specified per support; the check is skipped for supports with zero contact area.
Deflection checks (CSA O86:19 Cl.5.4.2 / NBCC Commentary D)
Three independent deflection limits are verified per span:
  1. Live/short-term deflection, governed by short-term serviceability load combinations; checked against a user-defined span/n ratio
  2. Long-term deflection, accounts for creep under sustained loads using the adjusted long-term modulus; checked against a separate span/n ratio
  3. Simplified DL+LL deflection, total dead-plus-live deflection checked against a third span/n limit
An optional absolute deflection limit in mm can be applied alongside any span-ratio limit. The governing deflection ratio per span is reported against each active limit.
Load linking
Support reactions are exported as linked outputs. When this beam is part of a larger project, connected column and footing calculations downstream automatically receive updated reactions whenever the beam inputs change, no manual re-entry of loads required.

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How to use it

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Key Properties

A. Size and GradeIn Calcs.com, you can select the size of the member you want from a list of industry-standard sized members by using the “Select” button. Using the corresponding filters, you can view available options based on the chosen type, species, grade, manufacturer, and nominal size.B. Number of PliesThe number of wood plies or boards in the beam. You need to have at least one board in your beam.C. Beam Plan LengthThe Beam Plan Length is equal to the length of the beam.D. Continuous Bracing For Lateral Torsional BucklingYou need to specify whether your beam has no continuous bracing, bracing continuous at the top edge only, bracing continuous at the bottom edge, or both. For sawn lumber, when you specify continuous bracing, Calcs.com will provide you with a short description of the CSA O86 requirements for bracing based on the width to depth ratio.E. Position of SupportsThis section is where you can select the support type or bracing type from a drop-down menu and then specify the location of each support/brace in millimeters (mm) or feet (ft) as measured from the leftmost position of the beam. Additionally, for each support, you must specify a bearing length in millimeters (mm) or inches (in) for a simple bearing check. To ignore bearing checks, simply enter a bearing length of 0.
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Loads

A. Load DiagramThe load diagram provides a live illustration of the beam and the assigned loading.B. LoadsLoads can be input as distributed, line, point, and moment loads in this section using the corresponding tables. You need to specify the location of the load in millimeters (mm) or inches (in) from the leftmost position and the respective load magnitude. To input load magnitude, select the load magnitude box or click the “Edit” text. For each corresponding load, a load magnitude table will appear where you will specify the type of load (Dead, Live, etc) and the respective magnitude in metric or imperial units.Load Magnitude table for Distributed Loads (kiloPascals (kPa) or pounds per square foot (psf))Load Magnitude table for Line Loads (kiloNewtons per meter (kN/m) or pounds per linear foot (plf)Load Magnitude table for Point/Moment Loads (kiloNewtons (kN) or pounds (lb) and kiloNewton-meter (kN*m) or pound-feet (lb*ft))C. Bending AxisCalcs.com requires you to specify if the beam is being loaded on the strong or weak axis. Calcs.com sets the default to the strong axis / joist (X-X). The strong axis corresponds to joist orientation and the weak axis to plank orientation.D. Self-WeightClearCallcs allows you to choose to include or exclude the self-weight of the beam in your calculations. The calculator is set to include the self-weight by default unless you specify otherwise. This can play a difference if you’re comparing against a published span table, where the self-weight of joists is often included in the superimposed dead load.
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Design Conditions

  • Service Condition: You need to indicate if the service condition is ‘dry’ or ‘wet.’ It is considered wet if the moisture content of wood will exceed 19% for an extended time. Typically, wet conditions apply to most exterior uses.
  • Effective Length Calculation Method: By default, Calcs.com uses the effective length calculation outlined by CSA O86:19, however, we conservatively take the effective length as 1.92L regardless of the loading condition. For a more accurate calculation, Calcs.com also provides you with the option to use the quarter-moment method outlined by the American Wood Council Technical Report 14.
  • Treatment: Calcs.com requires you to indicate if the wood beam is untreated, or if it is preservative-treated and whether it is incised (partially cut) or unincised.
  • System Factor: A system factor is considered if the member is part of a system where loads can be shared. There are three options for sawn lumber:
    • No System Factor: There are less than 3 beams spaced 610 mm apart and/or are not mutually sharing loads
    • Case 1 (for systems that don’t meet Case 2 requirements): There are more than 3 beams spaced less than 610 mm apart, mutually sharing loads
    • Case 2 (typical for joists and rafters): All of the following conditions are met
      • There are more than 3 beams spaced less than 610 mm apart, mutually sharing the load
      • Members are sheathed with a minimum of 9.5 mm OSB, waferboard, plywood or with min. 17mm lumber with panel coverings.
      • The sheathing is attached with sufficient stiffness and adequate spacing equal to 2 common nails at 150 mm on center at edges and 300 mm on center elsewhere.
    • For glulams and LVL’s the option is simply whether to consider a system factor or not - generally it can be considered if more than three parallel members are sharing load.
  • Storage Live Load: A storage live load is a live load (loads due to occupancy use) that occurs for a long duration. An example of this is storage in an attic. If this is set to yes, the duration factor associated with live load will be taken the same as dead load, and the load factor on live load will be increased in some combinations.
  • Consider Shear Deflection: Shear deflection can be a significant component of total deflection due to the low shear modulus. In particular, specifications for structural composites such as LVL often require that shear deflection be directly accounted for. If this is set to “Yes”, we use an approximation based on the peak moment within a span to find the shear deflection. This gives exact results for simply supported and cantilever spans with either a point load in the center or a UDL.
  • Absolute Deflection Limit: The maximum allowable deflection for the beam in millimeters (mm) or inches (in).
  • Live/Short-term Deflection Ratio: The maximum allowable deflection ratio for live and short loading. The default is L/360 but you may change this to a preferred ratio.
  • Long Term Deflection Ratio: The maximum allowable deflection ratio for long-term loading. The default is L/240 but you may change this to a preferred ratio.
  • Double Length/Allowable Deflection for Cantilevers: For cantilever spans, it’s typical to take “L” as double the span length. To adjust for this, the allowable deflection can be doubled.
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Summary and Graphs

In the summary section, the key parameters of your calculation will be outlined. In the graphs section, you can select the load combination you would like the see in the graphs.Additionally, in the associated tabs, below design conditions, you can see the respective parameters used to derive the summary figures and calculations. These include the following.
  • Load Combination Analysis
  • Unfactored Load Combination Analysis
  • Modulus of Elasticity (CSA O86:19 Section 6.3)
  • Bending Moment Resistance (CSA O86:19 Section 6.5.3)
  • Positive Bending (CSA O86:19 Section 6.5.3)
  • Negative Bending (CSA O86:19 Section 6.5.3)
  • Shear Resistance (CSA O86:19 Section 6.5.4)
  • Bearing (Compressive Resistance Perpendicular to Grain) (CSA O86:19 Section 6.5.6)
  • Deflections
These parameters were calculated based on the input loads and key properties.

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Available presets

Each preset opens the calculator with a typical setup already entered.

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Common questions

The calculator designs wood beams to CSA O86:19 (Limit States Design) with load combinations per NBCC 2015. Species and grade properties are drawn from the CWC Wood Design Manual 2017. Supported product types include sawn lumber, glulam, and SCL (LVL, PSL, LSL).
Key inputs include the wood section (species, grade, and product type from the built-in database), beam plan length, number of plies, service condition (dry or wet), treatment, support layout, loads by type (dead, live, snow, wind), lateral top-flange bracing spacing, and three independent deflection limit ratios.
The calculator checks factored bending moment resistance (M_f/M_r ≤ 1.0), shear resistance (V_f/V_r ≤ 1.0), bearing capacity at each support, governing live/short-term deflection, long-term deflection, and simplified DL+LL deflection, each against user-defined span ratios and an optional absolute limit. Lateral stability (slenderness ratio ≤ 50) is verified per CSA O86:19 Cl.7.5.6.4.
Yes. Multi-ply (built-up) beams are supported in strong-axis bending with any number of plies. Glulam checks use the CSA O86 simplified shear resistance method, valid for members with volume under 2 m³, the calculator enforces this limit automatically. LVL and other SCL products from major Canadian manufacturers are included in the section database. Weak-axis bending is supported for single-ply members only.
Use the section picker to filter by product type (sawn lumber, glulam, SCL), species group, and grade. The calculator loads CSA O86:19 tabulated reference design values automatically. You can also define a custom section by entering cross-section dimensions and manually entering design values if your species or grade is not in the built-in database.
Yes, beam reactions link directly to connected column and footing calculations in the same project. When you change a span, load, or section, all downstream calculations update automatically, no manual re-entry of reactions required.

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Next steps

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