A fence is only as good as the posts holding it up. When a fence starts leaning, a gate stops latching, or a deck feels a little off after a few winters, the cause is almost always below the ground. Here's what goes into setting posts that stay straight for years.

The main culprit: frost heave

Every winter the ground in Southwestern Ontario freezes deep. Wet soil expands as it freezes and grips anything set in it. If a post isn't set deep enough, the frozen ground can lift it a little more each winter. That's called frost heave. After a few seasons you see leaning sections, gaps between boards, and gates that drag or won't close.

Depth matters

The right depth depends on the height of the fence, the type of post, the soil, and whether it's a fence or a deck. What matters most is that the post goes deep enough to resist frost and hold steady against wind. Shallow holes are the number one shortcut that leads to problems later. Deck footings carry much more weight than fence posts and have their own requirements, so check with the City of London or your township about permits before you build a deck.

London's clay soil

Much of the London area sits on clay. Clay holds water, and wet soil is exactly what heaves the most when it freezes. That's why drainage at the bottom of the hole matters. A gravel base under the post helps water drain away instead of pooling around the bottom.

Concrete or gravel?

• Concrete is the most common choice and gives the strongest hold. The top should be shaped so rain runs away from the post instead of collecting against the wood.
• Gravel only drains well and makes a post easier to replace later, but it isn't as rigid. It suits lighter fences in soil that drains well.

Always call before you dig

In Ontario, you're required to request a free utility locate before digging, even for a few fence posts. Contact Ontario One Call at ON1Call.com, and give yourself a few days for the lines to be marked before work starts.

Hand-dug vs. machine-augured holes

A machine auger digs straight, clean, consistent holes, much faster than digging by hand and with less mess in your yard. On a fence with dozens of posts, that consistency is what keeps the line straight and the top even.

Planning a fence or deck this spring?

Spring is the busiest time of year for fence and deck work, so it pays to plan early. Straightline Post Hole Digging, a division of Classic Home Services, provides machine-augured post holes, post setting in concrete, custom fences and decks across London and area. Request a free quote.