I'm working on installing a fence post strong enough to support a wooden gate in Northern Ontario, specifically Sudbury. I know the frost line here is between 4 and 6 feet deep, and it's generally recommended to bury the posts deeper than that. However, since I'll be digging the hole by hand over the weekend and dealing with a lot of clay soil, I'm wondering about the need for 6 inches of gravel at the bottom of the hole for drainage. If I bury the post 3 to 4 feet deep and use tapered concrete footings like Bigfoot or Redibase, will that effectively prevent frost heave even if I'm still above the frost line? Also, I've come across mixed opinions about the strengths of dry concrete, wet concrete, and foam. I'm really curious about everyone's experiences with these different methods. For reference, I'm using a 10-foot 4x4 pressure-treated wood post and will be doing two posts about 3 feet apart for the gate. Sudbury experiences extreme weather, from +30C in the summer to -30C in winter during the polar vortex, so frost heave is a major concern. We also get a lot of snow, leading to sogginess in the spring.
3 Answers
Hey there! As a fellow Ontarian and contractor, I'd advise against digging that hole by hand. Renting an auger is super affordable and saves you tons of effort, turning what could be a 6-hour job into just about 30 minutes. Definitely dig deep enough for those gate posts—3.5 to 4 feet is good, and you'll want to make sure they're well below the frost line to keep that gate operational. For the other posts, setting them in gravel instead of concrete can help prevent frost heave. And on the topic of concrete types, when was the last time you saw a construction site using dry concrete or foam? They're just not the go-to in the industry—mixed concrete is always the preferred method!
This is more valuable than any post I've found so far, thanks for the advice!
Honestly, I think foam is a waste. I prefer tamped stone or concrete—Concrete’s just easier to work with. A lot of folks use Quickcrete with success. Belling the bottom of the hole is a smart move; it minimizes the chance of frost grabbing hold of the post. I usually fill the hole about two-thirds with cement, then backfill with dirt to prevent issues. This method has served me well with no problems!
You're likely to encounter some frost heave even at 4 feet deep. I recommend making the bottom of your hole bell-shaped and adding a few inches of gravel—this will help with drainage. You can then set the post in concrete or foam, but I would lean towards concrete for something really solid. That protects you from heaving better than foam.
That's the approach I was considering: dig 4 feet down, use 6 inches of gravel, and implement a belled concrete form. I'm also thinking of wrapping the post at ground level to keep water out with a plastic sleeve or Flex Seal.
Why just gravel for the non-gate posts?