A flagstone walkway is one of the few things you can add to a house that looks better at year twenty than at year two. The stone weathers in, moss finds the joints, and the path starts looking like it was always there. But there's a wide gap between a walkway built to last and a walkway built to sell, and you can't see the difference on the day it's finished. The difference is underneath.
What you're actually paying for
Ask three contractors to quote the same walkway and the numbers can be $3,000 apart. Almost all of that spread is base preparation, because the stone itself is the easy part.
In London and most of Southwestern Ontario, the ground under your walkway is clay. Clay holds water, and water here freezes and thaws dozens of times each winter. Every one of those cycles moves the ground. A walkway laid on a few centimetres of sand over undisturbed clay will look perfect in July and start pitching stones by the second spring. We spend a good part of every summer releveling flagstone that someone else installed on a shallow base.
A proper dry-laid installation means excavating roughly 20 to 30 cm down, laying a woven geotextile so the clay can't migrate up into the base, then building compacted lifts of granular stone before the bedding layer and the flagstone ever show up. When a quote is noticeably cheaper than the others, ask one question: how deep is the excavation? If the answer is vague, you've found where the savings come from.
Dry-laid or mortared
There are two honest ways to build a flagstone walkway, and they suit different situations.
| Dry-laid | Mortared (wet-laid) | |
|---|---|---|
| Build | Stone on compacted granular base, polymeric sand joints | Stone mortared onto a reinforced concrete slab |
| Feel | Natural, slight variation underfoot | Uniform, formal, dead flat |
| Winter behaviour | Flexes with frost, individual stones can be lifted and releveled | Rigid, fine until the slab moves, then joints crack |
| Repairs | Lift the stone, fix the spot, put it back | Cut out and re-mortar sections |
| Cost | Lower | Higher, you're pouring a slab first |
For most walkways in this climate, we'd rather build dry-laid. It moves with the freeze-thaw instead of fighting it, and any single stone that settles can be fixed in an hour without touching its neighbours. Mortared stone earns its price on front entrances and covered porches, where a dead-flat formal surface matters and the slab underneath is protected from the worst of the weather.
What it costs around here
Market pricing for professionally installed flagstone in Southwestern Ontario generally runs in these ranges: dry-laid work tends to land somewhere around $25 to $45 per square foot installed, and mortared work over a new concrete base runs roughly $45 to $70. Where a project falls inside those ranges depends on access (can a machine reach the site, or is everything coming through a gate by wheelbarrow), the stone you pick, how much excavation the ground needs, and what happens at the edges, steps and borders are slower work than field stone.
The stone itself is usually Ontario limestone or sandstone from quarries up around Owen Sound and Wiarton. Random flagstone costs less than dimensional (cut square) stone; thicker stone costs more but tolerates dry-laying better.
Treat those numbers as orientation, not a quote. Every yard we look at is different, which is why we price jobs after we've seen the site, the assessment costs you nothing.
How long it lasts
Built on a proper base, a dry-laid flagstone walkway is a 30-to-40-year installation, and the stone itself will outlive everyone reading this. What actually needs attention:
- Joints, every few years. Polymeric sand slowly washes and wears out of the joints. Topping it up is an afternoon job and keeps weeds and ants out.
- The odd settled stone. Even good bases settle a little at downspouts and high-traffic spots. One or two stones releveled every few years is normal; a wave running through the whole path is a base problem.
- De-icing salt, sparingly. Straight rock salt eats the surface of limestone and sandstone over time. Sand for grip, or a calcium-based melter used lightly, treats the stone much better.
If you've got an older walkway that's gone wavy, it can often be rescued. Lifting, rebuilding the base, and relaying the same stone costs well under a full replacement, because the expensive material is already sitting in your yard.
When flagstone is the wrong answer
It isn't always the right material, and it's better you hear that before spending money. If the budget is tight and the area is big, interlock pavers deliver a flat, durable surface for less. If you need a wheelchair-smooth surface, dimensional stone or pavers beat random flagstone, which always keeps a little texture and variation. And a small, simple dry-laid path is genuinely within reach of a patient homeowner willing to dig properly and rent a plate compactor, where DIY goes wrong is skipping the base to get to the pretty part. If that's the project you're weighing, our crews build outdoor stonework all season and are happy to give you a straight opinion on whether your plan needs us at all.
Frequently asked questions
How much does a flagstone walkway cost in Ontario?
Professionally installed dry-laid flagstone generally runs $25 to $45 per square foot in the London area, and mortared flagstone over a concrete base roughly $45 to $70. Site access, stone choice, and excavation conditions move the number, so treat ranges as orientation and get a site-specific quote.
Is dry-laid or mortared flagstone better?
In a freeze-thaw climate like Southwestern Ontario, dry-laid is usually the better walkway: it flexes with the ground and individual stones can be releveled cheaply. Mortared stone suits covered entrances and formal front walks where a perfectly flat surface is worth the extra cost.
How long does a flagstone walkway last?
The stone lasts practically forever; the installation is what ages. On a properly excavated and compacted base, expect 30 to 40 years with minor upkeep, joint sand topped up every few years and the occasional settled stone lifted and rebedded.
Can you fix a flagstone walkway that has become uneven?
Usually, yes. The stones are lifted, the base is rebuilt and compacted where it failed, and the same stones go back down. It costs well under a new installation because the material is reused, this is one of the most common jobs we do each spring.
Does flagstone work on clay soil?
Yes, but only with a real base. London's clay holds water and heaves with every freeze-thaw cycle, so the walkway needs 20 to 30 cm of excavation, geotextile over the clay, and compacted granular stone underneath. On clay, a shallow sand-bed installation is the reason so many local walkways fail within a couple of winters.