We are building a raised deck on clay type soil. The deck will surround the entirety of the house with the intention it will still be standing 20-30 years. The deck will be raised about 5 ft to meet the house.
We used EZ-tubes on the house for footing that were dug about 2 feet deep. For the deck we were thinking about using 6×6 pressure treated piers for simplicity.
I am wondering what type of recommended substrate would be most effective in a intensive clay soil. I was thinking either heavy gravel or poured concrete.
Any recommendations or positive experiences with longevity in this type of decking/substrate would be very helpful.
Best Answer
Alaska Man is right in that any deck attached to your structure must have the same type of frost footings that the structure does, otherwise it's likely to put strain on the building that it shouldn't.
Wooden deck posts are almost always set on concrete footings themselves--either poured or pre-cast. Only non-bearing fence posts should be on washed rock or gravel alone. For your purposes I'd probably put a few inches of washed rock down, then pour or place concrete pads on that to support the footing.
Your local inspection office will have specifics for you, even if you ask about it hypothetically. They'd know what works reliably in your area, and at what depth.