One of the most common questions we get about deck projects is whether a permit is actually required. The short answer is: for most decks in Ontario, yes. This article explains the rules, the process, and why skipping the permit is a decision that tends to come back around.
When a permit is required in Ontario ¶
Under the Ontario Building Code, a building permit is required for any deck that is attached to the house or that is more than 600mm (about 24 inches) above grade. In practice, this covers the vast majority of residential decks. Freestanding ground-level platforms below 600mm may not require a permit, but it is worth confirming with your municipality before assuming.
What the permit process involves ¶
A deck permit application typically requires a site plan showing the deck location relative to the property lines, a structural drawing showing the framing, post sizes, beam spans, and footing specifications, and sometimes a survey of the property. We prepare all of these documents as part of our project process. The permit is submitted, reviewed, and approved before any work begins. Inspections are required at the footing stage (before concrete is poured) and at the framing stage (before decking is installed).
What happens with an unpermitted deck ¶
An unpermitted deck creates two main problems. First, if the deck fails structurally and someone is injured, your home insurance may not cover the claim because the structure was not built to code and was not inspected. Second, when you sell the home, a real estate lawyer or home inspector will often identify an unpermitted structure, which can delay or complicate the sale. We have been called in to remediate unpermitted decks before a home sale more than once.
Composite versus pressure-treated: which is right for your project ¶
Pressure-treated lumber is less expensive upfront and is the standard choice for deck framing regardless of what the decking surface is made of. For the decking boards themselves, composite materials like Trex offer lower maintenance over time: no staining, no sealing, and resistance to splitting and warping. The upfront cost of composite is roughly 30 to 40 percent higher than pressure-treated decking, but most clients who have maintained a wood deck for several years find the trade-off worthwhile.
If you are planning a deck project this summer or fall, reach out early. Permit timelines and material lead times mean that the planning conversation should start well before you want to be sitting on the finished deck. See the questions we get asked most for more on our process.