Is There A Realistic Minimum Deck Height?

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Posted by: from Ottawa
11/5/2011 at 6:56:51 PM

We're just starting to design a replacement deck, to be built by some lucky contractor next spring, and had a question about the minimum height off the ground. Our yard grading sweeps gently down and away from our house, and the current two-level deck has the bottom level flush on the ground, we think with no joists underneath! (Hence, it's rotting?)

Does anyone know the building code for Ontario (Ottawa, in particular) with respect to whether it's a good idea to build the lowest deck level right on the ground, or is there a realistic minimum height that we could go by? This may determine whether the new deck can be multi-level or not, which has tremendous impact on design possibilities. For example, are you required to have a 2x8" joist underneath the deck in all places, and thus the height of the lowest level is most likely 10" off the ground? We could simply design a one-level deck, but I must admit that a two-level deck is more interesting.

Any ideas? Suggestions? Knowledge of deck building code?

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Date/Time11/5/2011 at 7:26:32 PM

I was just in Ottawa this week. I saw a townhouse project that had removed the patio stones and built the deck with 2x6 joists.

I was told that they dug out some of the soil and used it for grading. They then added gravel and that weed blocking fabric.

The deck board were flush with the grass at the house. It looked good. Not sure how long it will last. You could use the blue wood and treat it again.

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Dave from 360renos in Navan
Date/Time11/18/2011 at 3:11:33 PM

Good Afternoon Jennifer,

Generally you want your deck off the ground enough to allow for adequate air flow underneath letting the deck dry out between rainfalls and not to have the ground moisture get trapped under the deck.

There is no minimum height the deck is required to be at. There is Building Code however for decks that are over 24" in height with regards to railings, footings and cantilevering. You would have joists as this is what the deck boards are attached to. You may not have beams or they could be rotted.

You can build with 2x6, 2x8, 2x10 or larger if you wish. The Contractor building the deck must follow Building Code for joist spans and spacing and beam well as code for cantilevering beyond the beams if desired. When the Contractor applies for a Building Permit all these items are checked and verified by the City Planning Dept. before the plans are approved.

I have built a few decks close to the ground and used some ideas to have adequate airflow under the deck. A deck close to the ground looks great with its open space as it does not have railings and blends in nicely as additional space for your home.

If there is anything else I can answer or help out with such as designing a deck or offering you a quote Jennifer, please do not hesitate to contact me.



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