A low door threshold makes shallow framing tempting. Then someone says, "Just use 2x6s." The useful follow-up is: how far will they span, and what will support them?
Three measurements that sound interchangeable
| Measurement | What it describes |
|---|---|
| Joist depth | The size of the structural member, such as nominal 2x6. |
| Joist span | The distance the joist carries between supports. |
| Joist spacing | The distance from the centre of one joist to the next. |
A twelve-foot-long deck does not automatically have a twelve-foot joist span. An intermediate beam can change that. Conversely, placing joists closer together does not make every long span acceptable.
What the local example establishes
Oakville's sample drawings, sheet A-5, include 2x6 joists in a span table. So a blanket claim that Ontario never allows them is unhelpful. The same table distinguishes joist spacing and cantilever conditions.
The sample is an application aid, not a design approval for your property. Have the designer confirm the applicable lumber species and grade, loading, bearing, and current requirements rather than copying an isolated number from the drawing.
Shallow framing comes with a layout decision
Imagine choosing between a deeper joist and another support line. The shallower option may preserve a little height near the door, but the additional beam and footings take space and money. Under a low deck, access to those connections can also become awkward.
That is the comparison to price: two complete framing arrangements. A cheaper piece of lumber is not necessarily a cheaper deck.
Get these details onto one drawing
- Actual support locations and joist spans, with any overhang shown separately.
- Joist size, spacing, species and grade, plus the decking product and direction.
- Any roof, hot tub, or other special load the designer must account for.
- Finished deck height and the route water will take away from the doorway.
Oakville's deck application guidance asks for structural and site information together. That is sensible: the joist choice, footing layout, and finished height belong to the same decision.