I'm building a pergola that's open at the top, and I'm planning to install six concrete footers for support. The posts I'm using are 3 meters tall and 10 cm wide, and they will rest on the footers secured with braces. I've looked into the frost line, which is 30 cm where I live, but I've heard that if your soil is clay, you might need to dig even deeper. Additionally, it's quite windy in my area, but since the pergola has no roof, I'm not sure how much that will affect the depth I should dig. How deep do you think I should go for the footers? I'm trying to minimize the amount of concrete I use and the labor involved in digging, especially since the soil here is rocky and clay-filled, and I mainly have a digging bar and shovel at my disposal.
4 Answers
Just a heads up—if you ever decide to add a roof to your pergola, you'll want to rethink the footer depth. Wind can definitely become a concern if there's a structure above it. Best of luck with your build!
If you're dealing with tough soil, it might be worth looking into renting a fence post auger. They can really speed up the digging process! As for depth, I recently dug footers that were about 75 cm deep and they’ve held up well, so you might want to consider going a bit deeper than the frost line if possible. It gives you extra insurance against wind!
It's great that you're thinking about stability! Even though it's just a pergola, I recommend digging your footers at least 15 to 18 inches deep (around 45 cm). I've done footers before, and in my area, the frost line is about 36 inches, so I usually go for around 40 inches just to be safe. If you’re worried about saving concrete, try using sonotubes—they really help with that! For added stability, set the sono tube up an inch or two and secure it with a board and screws so the concrete can flare out a bit at the bottom. Also, here's a pro tip: using a pressure washer to clear away dirt works wonders and saves your back!
Does the pressure washer really work on clay? I’ve never tried it.
Honestly, checking out some local guidelines or even a chat AI like ChatGPT can help you with location-specific info!
Good tip about the sonotubes! Definitely makes things easier.