Understanding Deck Beam Span Tables in Ontario's Building Code
When planning a deck construction in Ontario, it's crucial to adhere to the provincial building code to ensure safety and structural integrity. One key aspect of this is understanding the deck beam span tables outlined in the code. This guide will help you navigate these tables and understand their significance in your deck building project.
Why Deck Beam Span Tables Matter
Deck beam span tables are essential for determining the size and spacing of the beams that support your deck. They take into account the load that the deck will bear, the type of material used for the beams, and the span between supports. By following these tables, you can ensure that your deck is strong enough to support the intended loads and safe for use.
Ontario's Building Code Requirements
Ontario's Building Code, under Division B, Section 9.24, provides guidelines for the design and construction of decks. It specifies that decks must be designed to support a live load of 2.0 kN/m² (40 psf) and a concentrated live load of 0.9 kN (200 lbs) at any point on the deck. The code also outlines the maximum allowable spans for deck joists based on the type of material used.
Maximum Allowable Joist Spans
The maximum allowable joist spans, as per the Ontario Building Code, are as follows:
- 2.4 m (8 ft) for 38 mm (2x8) joists
- 3.0 m (10 ft) for 51 mm (2x10) joists
- 3.6 m (12 ft) for 64 mm (2x12) joists
These spans are based on the assumption that the joists are made of No. 2 grade Douglas Fir-Larch or equivalent and are spaced at 406 mm (16 inches) on center.
Deck Beam Span Tables
To determine the size and spacing of your deck beams, you can refer to the following tables, which are based on the Ontario Building Code:
| Beam Material | Beam Size (mm) | Maximum Span (m) |
|---|---|---|
| Douglas Fir-Larch (No. 2 grade) | 51 | 3.6 |
| Douglas Fir-Larch (No. 2 grade) | 76 | 4.5 |
| Pressure Treated Lumber | 51 | 3.0 |
| Pressure Treated Lumber | 76 | 3.6 |
These tables provide the maximum allowable span for a given beam size and material. They assume that the beams are spaced at 1.2 m (4 ft) on center and support joists that are spaced at 406 mm (16 inches) on center.
Factors Affecting Beam Span
Several factors can affect the maximum allowable beam span, including:
- The load that the beam will bear, including both live loads (like people and furniture) and dead loads (like the weight of the decking and railings)
- The type of material used for the beam
- The spacing of the beams and the joists they support
- Any additional loads, like snow or ice, that the beam may need to support
If your deck has unique features, like a hot tub or a complex shape, you may need to consult with a structural engineer to determine the appropriate beam size and span.
Conclusion
Understanding deck beam span tables is crucial for building a safe and durable deck in Ontario. By following the guidelines outlined in the provincial building code and using the tables provided in this guide, you can ensure that your deck is structurally sound and compliant with the law. If you're unsure about any aspect of your deck design, it's always a good idea to consult with a professional engineer or a building inspector.