Retaining Wall Contractor in Markham — Segmental Block, Armour Stone & Poured Concrete

We build retaining walls across Markham — from short 0.5m garden terraces in Berczy Village to 2.5m engineered block walls in Cathedraltown and armour stone tiers in Unionville. OCM Excavation & Construction has been working Markham yards since 2008, and we handle the full stack: site survey, drainage design, P.Eng coordination over 1.0m, Markham Building Permit paperwork, the dig, the wall, and the backfill. Call 416-317-3090 for a Markham site visit.

Why retaining walls in Markham need local skill

Markham is not one site condition — it’s a dozen. A wall in old Unionville behaves nothing like a wall in Cornell, and pricing a job without driving the lot is how contractors get burned.

• Rouge River corridor (Box Grove, Cornell, Cornell Rouge): properties near the valley fall under TRCA Ontario Regulation 41/24. Walls inside the regulated area need a TRCA permit on top of the Markham Building Permit, and the setback line from the top-of-bank dictates where the wall can actually sit.
• Markham SALT By-law 2011-232: if your wall job moves more than 300mm of fill across the property, a Site Alteration permit kicks in. Most short garden walls don’t trigger it; tiered walls with major regrading often do.
• Markham Tree By-law 2023-164: any tree 20cm DBH (measured at 1.37m) is protected. We map the tree protection zone before we cut the bench so the excavator doesn’t strip roots that buy us a stop-work order.
• OBC retaining wall threshold: anything over 1.0m exposed height needs a Building Permit and a P.Eng-stamped design. We don’t pretend a 1.4m wall is “0.99m” to skip the engineer — that’s how walls fail in year five.
• Unionville heritage character: the older streets favour armour stone over machine-cut block. We match material to the streetscape so the wall doesn’t look transplanted from a big-box parking lot.
• Cornell rear-lane access: we run material and spoil through the lane on the right jobs, which saves the front sod and the neighbours’ patience.

Types of retaining walls we build in Markham

• Segmental concrete block (0.5m–2.5m): Allan Block, Versa-Lok, Oaks Proterra. Fastest install, geogrid reinforcement built into the design, broad colour range. Workhorse wall across Berczy Village, Greensborough, and Markham Village.
• Armour stone (1m–3m): large quarried limestone blocks, often 1–3 tonnes each. The right call for Unionville and Cathedraltown estate lots where the wall has to read as landscape, not as infrastructure. See our armour stone installation page for build detail.
• Poured concrete: structural choice for driveway walls, walkout basements, and any wall where height plus surcharge load (a parked vehicle, a pool deck) makes block borderline. Formed, reinforced, and stamped.
• Gabion baskets: wire cages filled with clear stone. Free-draining, well-suited to TRCA-sensitive ravine edges where rigid walls aren’t approved.
• Pressure-treated timber: short garden walls under 0.6m. We still build them when the budget and the use case fit — but we won’t sell you timber where block belongs.

Our retaining wall process in Markham

1. Site walk and design: we measure exposed height, total length, surcharge above, drainage daylight points, and access. We flag any TRCA exposure on east-side lots and any protected trees inside the work zone.
2. Geotechnical review: on walls over 1.2m or on suspect fill (newer subdivisions on engineered backfill behave differently than mature Markham Village clay), we order a soils review.
3. P.Eng stamp over 1.0m: per OBC. The engineer specifies geogrid layers, base width, drainage detail, and reinforcement spacing.
4. Permits: Markham Building Permit, Site Alteration under SALT By-law 2011-232 if regrading triggers it, TRCA permit if regulated, and a tree permit under By-law 2023-164 if protected trees are touched.
5. Bench cut and base prep: over-excavate behind the wall line, compacted granular base — typically 150–300mm of 19mm Granular A depending on wall height.
6. Drainage: 100mm perforated drain pipe behind the wall, clear stone chimney drain, geotextile separation layer, daylight outlet to grade or storm.
7. Wall build and backfill: course by course, geogrid layers as specified, granular backfill compacted in lifts.

Grading the surrounding yard so water flows away from the wall, not against it, is part of the scope. If you need topsoil and sod work tied in, see our Markham land grading page.

What affects retaining wall cost in Markham

• Exposed height: drives reinforcement, base width, and whether you’re paying for a P.Eng.
• Total length: longer runs amortize mobilization and lower per-square-foot cost.
• Material: segmental block sits lowest, poured concrete in the middle, armour stone highest on a per-face-square-foot basis — but armour stone on an estate Cathedraltown lot can be the only material that fits the property aesthetic.
• Drainage and grading scope: a wall on a slope that needs swales, catch basins, or storm tie-ins costs more than a wall on a flat lot.
• P.Eng fees: required over 1.0m exposed height.
• Markham Building Permit fees: per the City’s current schedule.
• Tree permit fees: under By-law 2023-164 if a protected tree is removed or its critical root zone is encroached.
• TRCA permit: if the wall is inside the Rouge River regulated area.
• SALT permit: if total fill movement on the property crosses the 300mm threshold under By-law 2011-232.
• Access: rear-lane Cornell jobs and full-size-access Cathedraltown jobs are cheaper to dig than walled-in Unionville heritage lots that need a mini-excavator and wheelbarrow runs.

For the wider regional view on materials, engineering, and permit triggers, see our retaining wall construction across Toronto and the GTA page. If your retaining wall is paired with broader site work — basement walkout, driveway re-grade, pool excavation — our Markham excavation crew handles the whole package.

FAQ — Retaining walls in Markham

Do I need a permit for a retaining wall in Markham?

Under the Ontario Building Code, retaining walls with more than 1.0m of exposed height require a Markham Building Permit and a P.Eng-stamped design. Walls shorter than that usually don’t need a Building Permit, but if your job moves significant fill, Markham’s SALT By-law 2011-232 can trigger a Site Alteration permit at the 300mm threshold. Rouge corridor lots may also need a TRCA permit.

How long does a typical Markham retaining wall job take?

A short segmental block wall — say 10m long, 0.8m tall — is usually a 3–5 day build once permits are in hand. A tiered armour stone job in Unionville with drainage, grading, and softscape integration can run 2–3 weeks. Engineering and permit timelines add to the front end, not the build itself.

Armour stone or segmental block for a Unionville property?

For mature Unionville and Cathedraltown streetscapes, armour stone usually reads better against the heritage character — it ages into the landscape instead of standing out. Segmental block is the right pick where the wall is hidden, where geometry is tight, or where budget rules. We’ll show you both costed out before you commit.

Will my retaining wall affect protected trees in the yard?

Any tree 20cm DBH or larger on your Markham property falls under Tree By-law 2023-164. We map the tree protection zone before excavation, route the bench cut around it where possible, and pull a tree permit if removal or significant root encroachment is unavoidable. Working around trees usually adds days, not weeks, when planned up front.

To book a Markham site visit, call 416-317-3090 or use the free quote form.

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