I would like to build a deck 2 feet off the ground, the area right now is covered by patio stones 18"x18". I need to remove those stones and dig about 6-8in, in order to keep the deck below 2 feet using deck blocks and adjustable deck support... is this ok to do or do I need to dig deeper to below the frostline- im in east Toronto...
As long as you're OK with a little seasonal frost movement there's nothing wrong with your idea and it's OK with respect to building code since the deck is less than 2' above grade.
When I worked for New Home Warranty I witnessed MANY failures involving decks supported by pilings frost-jacking (particularly homes with walkout basements) where the pile lifts and doesn't settle back over the next summer. it would have been better to use pad footings and allow for some seasonal fluctuation.
If those pads are supported on a thick gravel base it helps to reduce or eliminate frost movement depending on the thickness. Also pad footings supported on gravel soils are not required by Code to be below frost level.
As per Ian, good advice. Anything under 2 ft you do not need a permit but why not do it as well as possible? as you will get movement in Canada without pilings to code. Screw piles are not expensive $200 each, doing it this way will "guarantee" a pro job and "no" movement in future if at least 8ft pilings used. While there are exceptions in 20 years I have never had as call back doing it this way but many decks with just blocks invariably always move some or alot over the years.
Make sure to check your municipality in regards to the deck height. Just because you're 2' and under, it still needs comply with other requirements for it not to have a permit.
Other than that, what others have said, if you're okay with slight seasonal movement, you should be fine. The very first deck I ever built is on deck blocks on top of patio slabs and it doesn't even look like it's moved an inch.
Good luck with your project!
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