Armour stone retaining walls are a very popular way of adding timeless beauty and functionality to your garden, especially if your garden has different elevations. Armour stone is natural stone and is quarried mainly by two different methods: drilling or blasting the rock face, and peeling off layers of stone with an excavator.
Quick answers
Short, direct answers to the questions homeowners ask most about natural stone retaining walls.
- What is an armour stone retaining wall?
- An armour stone retaining wall is a gravity wall built from large blocks of quarried natural stone that hold back soil with their own weight and friction, without interlocking. Top Mark builds them across Toronto and the GTA from wall-grade stones about 12–14″ high and over a tonne each, hand-picked at the quarry so every course sits tight and level.
- What is the difference between armour stone and Eramosa?
- Armour stone comes in big, rugged blocks, ideally a uniform 12–14″ high and over a tonne each, placed by machine. Eramosa is an Ontario natural stone from the Owen Sound area, cut into 8″ and 4″ pieces and dry-stacked in courses for a more formal, striped look. Many Top Mark walls across the GTA use both, with armour stone anchoring the ends and steps.
- Does a natural stone retaining wall need a concrete footing?
- No. A dry-stacked natural stone wall is somewhat flexible, so it doesn’t need a rigid concrete footing, even with Toronto’s frost. It does need a solid base of mechanically compacted gravel, with clear-stone backfill, filter fabric and socked weeping tile behind it. Top Mark’s process starts with that base, so water drains away instead of building pressure behind the stone.
- When does a natural stone wall need geo-grid?
- Geo-grid is added when the site conditions and soil call for it, typically on taller walls or where there’s a lot of soil to hold. The flat polymer mesh is laid between courses and run back into the compacted backfill, so the wall and soil act as one heavier mass. On the Jancy King wall in Toronto’s High Park, Top Mark placed geo-grid every 24 inches of height.
- Do I need a permit for a stone retaining wall in Toronto?
- Sometimes. In Ontario, a retaining wall with more than 1 m (about 3′3″) of exposed face beside public property, a building entrance or private property the public uses generally needs a building permit and a professional engineer’s design. Ravine lots may also fall under Toronto’s ravine by-law or TRCA rules. Top Mark sorts this out with you during planning; always confirm with your municipality.
- How is a natural stone retaining wall priced?
- Stone walls are usually priced per square foot of wall face (length × exposed height), while the stone itself is sold by the ton and some quotes come per linear foot, so compare quotes in the same unit. Height, machine access, drainage, removal of the old wall and steps move the price most. Top Mark’s retaining wall cost guide explains typical Ontario and GTA ranges.
We are fully equipped to service residential, commercial and industrial clients across Toronto and the GTA, from Thornhill, Vaughan, Richmond Hill and Markham to Mississauga, Burlington, Hamilton and surrounding areas.
Wall-grade armour stone, hand-picked at the quarry
Traditionally, armour stone is quarried by drilling and blasting, so its final size, shape and quantity could not be guaranteed. These types of armour stones are great as accent pieces but are not recommended for retaining wall construction, as they cannot be stacked effectively.
For retaining wall construction, armour stones of uniform height with smooth surfaces are the best. Usually, stones that are about 12–14″ in height and weigh in excess of a tonne are best suited for retaining wall construction. We obtain our armour stones directly from the quarry, and each stone is hand-picked at the quarry to ensure that it is best suited for retaining wall construction.
How an armour stone retaining wall holds back soil
Stand-alone armour stone retaining walls can be categorized as gravity retaining walls: they use their sheer weight to retain the soil behind them. Armour stone retaining walls do not interlock, and each stone is held in place by gravity and friction. Since these walls are somewhat flexible, they can absorb movement without undermining the structural integrity of the retaining wall. Depending on the site conditions and soil characteristics, geo-grid may be incorporated into the retaining wall design to stabilize the backfill and to act as a tie-back.
The wall’s strength comes from heavy stones sitting flat and tight against each other, a slight step back into the slope on each course, and a backfill zone that stays drained. Geo-grid is a flat polymer mesh laid between courses and run back into the compacted backfill, so the wall and the soil behind it act as one heavier mass.
Foundation and drainage come first
Dry-stacked gravity walls are somewhat flexible and do not require a rigid footing in frost areas. However, a solid foundation constructed with mechanically compacted gravel is an absolute must. Proper drainage to dissipate the groundwater behind the retaining wall, and drainage material to minimize hydrostatic pressure, will help prevent the retaining wall from suffering premature structural failure.
Drainage and frost in Toronto
Toronto walls go through many freeze-thaw cycles each winter, and many lots across Toronto and York Region sit on slow-draining clay. Water trapped behind a wall adds pressure, and when it freezes it expands and pushes on the stone. A dry-stacked wall can live with a little seasonal movement, but only if the water has somewhere to go:
- Mechanically compacted ¾″ gravel base
- Clear ¾″ gravel backfill that drains freely
- Non-woven filter fabric between soil and gravel
- Perforated, socked weeping tile at the base
- Geo-grid tie-backs where the design calls for them
- A clear path for collected water to drain away
Choosing your stone: armour stone or Eramosa
There are two main ways to build a wall in natural stone: large armour stone, or cut coursing stone such as Eramosa. Many walls, like the Sandy Dix garden wall below, use both.
Armour stone
Big blocks with a bold, rugged face, ideally a uniform 12–14″ high so they stack tightly. Stones over a tonne need machine access. Best for larger grade changes, steps and corner bookends.
Eramosa “Tiger Stripe”
An Ontario natural stone from the Owen Sound area, cut into 8″ and 4″ high pieces and dry-stacked in courses. Its striped grain and crisp lines give a more formal look, and matching Eramosa coping and stair treads finish it.
Using both
Armour stone anchors the ends and steps, while lighter coursing stone fills the runs between them. The big stones add character while saving material cost.
If you want armour stone mainly as a feature rather than a structural wall, see decorative natural stone.
How we build a natural stone wall
- Site visit & free consultationWe look at the grade, the height you need to retain, the soil, drainage and access for machinery, and what has to come out first.
- Design, stone & permitsTogether we choose armour stone, Eramosa or a mix, decide whether geo-grid is needed, and check whether the height and location call for a permit or an engineered design.
- Remove & excavateThe old timber, rockery or concrete comes out, and we dig for the base, the drainage zone and any geo-grid.
- Base & drainageGravel is mechanically compacted and levelled so the first course sits firm, just below finished grade, with filter fabric and socked weeping tile behind.
- Stack, backfill, repeatEach stone is set tight to its neighbours, joints staggered and stepped back slightly into the slope. Clear gravel goes in behind every course, with geo-grid between courses where the design calls for it.
- Coping, steps & plantingNatural stone coping finishes the top and is bonded in place. Stairs, topsoil and planting complete the job.
Permits and engineering
A low stone border around a flower bed rarely needs anything from the city. Height and location are what change that. Once the exposed face of a retaining wall passes 1 m (about 3′3″) and the wall stands beside public property, a building entrance or private property the public uses, Ontario generally calls for a building permit and a design by a professional engineer. Sloped lots that back onto a ravine or creek can also fall under Toronto’s ravine and natural feature protection by-law or Toronto and Region Conservation Authority (TRCA) rules. Every municipality runs its own process, so confirm the details with yours; sorting this out is part of how we plan a stone wall with you.
Need a wall over 3 feet?
Design and permits can take considerable time and resources, so contact a specialized retaining wall contractor well in advance. Call 416.728.2159 for a free consultation.
Natural stone vs precast vs small block
Natural stone compared with the two precast options we build:
| Natural stone | Large precast block | Small precast block | |
|---|---|---|---|
| What it is | Quarried armour stone, or cut stone such as Eramosa | Concrete blocks over 100 lb each; some weigh 5,000 lb | Concrete blocks under 100 lb each |
| How it holds | Weight and friction; stones don’t interlock | Interlocking courses in a running bond, with a batter | Interlocking courses in a running bond, with a batter |
| Movement | Somewhat flexible; absorbs minor movement | Fairly rigid; acts as one unit | Fairly rigid; acts as one unit |
| Earth pressure | Resisted by mass, so it needs depth; geo-grid where required | Interlocked, so even a slender wall resists more than armour stone of the same depth | Same principle, but limited load-bearing capacity |
| Best for | Garden tiers and grade changes where looks matter most | Medium to heavy-duty walls, usually above 5′, or walls carrying extra loads | Light-duty walls under 6′ with no load surcharge |
| Site access | Machine needed for tonne-plus armour stone; cut Eramosa can be set by hand | Heavy equipment for the largest blocks | Good where access is limited |
| Look | Natural colour and grain; no two stones alike | Manufactured face: split, smooth or textured | Many shapes and sizes; one of the most cost-effective options |
Read more about precast block walls and small block walls, or see all three side by side on our projects page.
Sandy Dix Garden Wall
The original garden retaining wall was a three-tiered wooden retaining wall made of 6×6 pressure-treated timber. The wood had been installed for a few decades and was extensively rotten. It had lost much of its aesthetic appeal and was infested with insects and mould, as well as being unsafe.
The replacement wall was made of an Ontario natural stone quarried in the Owen Sound area. The stone, known as Eramosa or ‘Tiger Stripe’, was dry-stacked using a combination of 8-inch-high and 4-inch-high pieces. Each tier of the wall was ‘bookended’ with a large piece of armour stone to provide visual appeal while saving material cost.
The stone was laid on a bed of ¾-inch gravel and dry-stacked, with gravel placed behind the wall for drainage. A 12-inch × 2-inch natural Eramosa stone coping was glued atop each tier of the wall.
- Before
- Rotten 3-tier 6×6 timber wall
- Stone
- Eramosa “Tiger Stripe”, Owen Sound
- Coursing
- 8″ and 4″ pieces, armour stone bookends
- Finish
- 12″ × 2″ Eramosa coping, glued
Jancy King Wall
This home in Toronto’s High Park district originally had an informal, tiered rockery-style retaining wall. The homeowners wanted a more formal look, with a tiered planter-style wall. The original stairs were solid concrete; they had cracked and were unsafe.
The replacement wall was made of dry-stacked, 8-inch-high Eramosa natural stone from the Owen Sound area of Southern Ontario. The wall was laid on a base of ¾-inch gravel and backfilled using ¾-inch clear gravel. Non-woven filter fabric was used to separate the sandy soil from the clean gravel, and flexible 4-inch socked weeping tile was used behind the wall for drainage. Geo-grid mesh was used as tie-back material every 24 inches in height for structural support.
The two sets of stairs were both made of rough-finished (bush-hammered) Eramosa treads, individually set on a concrete base. The top coping of the entire wall is natural Eramosa stone for visual appeal.
- Location
- High Park, Toronto
- Stone
- Dry-stacked 8″ Eramosa
- Behind the wall
- Socked weeping tile, geo-grid every 24″
- Stairs
- Bush-hammered Eramosa, two sets
Common questions about natural stone walls
What advantages do natural stone walls offer?
Natural stone walls provide a range of benefits, such as lasting durability, visual charm and minimal upkeep. They withstand the weather and maintain their appeal for years with little maintenance. Moreover, stone gives any property a sophisticated appearance, elevating its overall worth and attractiveness.
How long do natural stone walls typically last?
When constructed correctly and cared for properly, natural stone walls can endure for decades, often exceeding 50 years. Their longevity depends on factors like the type of stone used, the quality of the construction work and the environmental conditions in the area. Regular checks and timely repairs can prolong their life even further.
Which types of stone are commonly used to build walls?
Granite, limestone, sandstone, slate and fieldstone are among the most commonly used natural stones in wall construction. Each variety offers its own characteristics and visual appeal, enabling an array of styles and finishes to suit diverse tastes and architectural concepts. Both projects on this page use Eramosa, a striped Ontario limestone from the Owen Sound area.
What does a natural stone wall typically cost?
The cost of erecting a natural stone wall varies depending on factors like the type of stone chosen, the size and intricacy of the structure, and the amount of labour required.
On average, the cost of a stone wall can vary from $25 to $75 per foot. It’s recommended to ask for a quote to get an estimate tailored to your specific project.
Can natural stone walls be both functional and decorative?
Absolutely. Natural stone walls can serve both functional and aesthetic purposes. Retaining walls are intended to retain soil and prevent erosion, while decorative walls can enhance landscaping, define boundaries or create seating areas. The selection of stone type and construction method will depend on the intended use of the wall.
Are stone walls eco-friendly?
Natural stone walls are seen as eco-friendly because of their durability and the minimal processing needed compared to other construction materials. They do not emit harmful substances, and the stone can be obtained locally to reduce transportation emissions. Furthermore, natural stone is a material that can be repurposed or recycled.
How should I care for a stone wall?
Taking care of a stone wall is straightforward:
- Regular check-ups: look for loose stones, cracks or any signs of damage.
- Cleaning: use water and a gentle detergent to clean the surface and remove dirt or moss.
- Repointing: on mortared walls, replace weakened mortar to maintain strength.
- Repair: address any damage promptly to prevent bigger problems.
By following these guidelines you can preserve the durability and appearance of your stone wall. A dry-stacked wall has no mortar to repoint, so check instead that the coping is still secure and that water drains away freely after heavy rain.
Should I install a natural stone wall myself or hire a professional?
While it’s feasible to install a stone wall yourself, it demands considerable expertise and experience to ensure both structural integrity and visual appeal. Hiring a professional guarantees that the wall meets standards, adheres to local building regulations and saves you time and energy. Professionals also have access to the required tools and materials, including the machinery to place tonne-plus armour stone.
