Hardscape Construction and Installation

Construction and Installation of Hardscapes (Landscape Masonry)

Chapter Introduction

The installation of hardscapes — or landscape masonry — is one of the heaviest and most structurally demanding tasks in the landscaping and horticulture trade. This chapter covers all the theoretical and practical knowledge required for the Red Seal exam: slabs, pavers, retaining walls, steps, foundation walls, drainage, and thickness calculations. You must master not only the technical skills but also the engineering principles that ensure the durability of structures against frost, water, and mechanical loads.

Fundamental Principles of Hardscape Construction

Soil Bearing Capacity and Load-Bearing Capacity

Every hardscape structure rests on the soil. The bearing capacity of a soil is the maximum pressure it can support without excessive settlement or failure. It is expressed in kilopascals (kPa) or tonnes per square metre (t/m²). For the exam, remember the following indicative values:

Soil Type	Approximate Bearing Capacity (kPa)
Solid rock	300 – 400
Compacted gravel	200 – 300
Compacted coarse sand	150 – 250
Fine sand	100 – 150
Firm clay	75 – 150
Soft clay / peat	< 50

Golden rule: if the bearing capacity of the natural soil is insufficient, you must excavate and replace it with compacted granular material (0–20 mm or 0–56 mm gravel) in layers of 150 mm maximum, each compacted to 95% of modified Proctor density.

Frost and Frost Heave

In Canada, seasonal frost is the leading cause of hardscape failure. Water in the soil freezes and expands by approximately 9%. This phenomenon creates ice lenses that lift structures. Three conditions are necessary for frost heave: frost-susceptible soil (silt, clay), a water table, and sub-zero temperatures.

The frost depth varies by region: from 1.2 m in southern Ontario to over 3 m in the Canadian North. For the exam, a frost depth of 1.2 m to 1.5 m is generally considered for load-bearing wall foundations, and 600 mm to 800 mm for non-load-bearing slabs and pavers.

Frost protection strategies:

Excavate below the frost line for load-bearing wall foundations.

Use non-frost-susceptible materials (gravel, crushed stone) under slabs.

Provide adequate drainage to remove water before it freezes.

Perimeter insulation (extruded polystyrene panels) in certain cases.

Base Materials

Aggregates

Aggregates are classified by size and origin. For hardscape construction, the following are used:

Crushed stone 0–20 mm: for slab and paver foundations.

Crushed stone 0–56 mm: for thick base courses.

Compaction sand (0–5 mm): for paver installation and levelling.

Mortar sand: for joints and setting beds.

The gradation (particle size distribution) must be continuous to ensure proper compaction. A well-graded material contains particles of all sizes, allowing for optimal interlocking.

Concrete

Concrete is a mixture of cement, water, and fine and coarse aggregates. Its strength is designated by the letter F followed by a number: F'c = 20 MPa (megapascals) for light foundations, F'c = 30 MPa for more demanding structures.

Application	Recommended Minimum Strength
Footings	20 MPa
Cast-in-place concrete slabs	25 MPa
Reinforced concrete retaining walls	30 MPa
Steps and stairways	25 MPa

Concrete must be placed within 2 hours of mixing, at a minimum temperature of 5 °C. In cold weather, accelerating admixtures and thermal protection are used.

Pavers and Slabs

Concrete pavers (interlocking pavers) have a standard thickness of 60 mm, 80 mm, or 100 mm. Patio slabs (large-format pavers) typically measure 600 × 600 mm or 600 × 400 mm, with a thickness of 50 mm.

Natural stone pavers (granite, sandstone) are more durable but more expensive. Their thickness ranges from 30 mm to 80 mm depending on the application.

Foundations and Footings

Footings for Load-Bearing Walls

A footing is a concrete base that distributes the wall load onto the soil. Its dimensions depend on the load and the soil bearing capacity.

Calculating the minimum footing width:

Width (m) = Total load (kN/m) ÷ Allowable bearing capacity (kPa)

Example: A 1.5 m high retaining wall made of concrete blocks weighs approximately 15 kN/m. If the soil has a bearing capacity of 150 kPa:

Width = 15 ÷ 150 = 0.10 m

However, a safety factor of 2 to 3 is applied, so the footing will be at least 300 mm wide. In practice, for a 1.5 m retaining wall, a footing of 450 to 600 mm wide and 200 to 300 mm thick is planned.

Practical rules for footings:

Minimum thickness: 150 mm for unreinforced footings, 200 mm for reinforced footings.

The footing must extend 100 mm beyond each side of the wall.

Concrete must be placed on unfrozen, clean, compacted soil.

Foundations for Slabs and Pavers

For slabs and pavers, the foundation consists of:

46.Natural soil excavated and compacted.

47.Geotextile (optional) to separate the soil from the aggregate.

48.Base course of compacted crushed stone 0–20 mm.

49.Setting bed of sand (for pavers) or mortar (for slabs).

Recommended thicknesses:

Application	Crushed Stone Thickness	Setting Bed
Pedestrian walkway	100 – 150 mm	25 mm sand
Patio	150 – 200 mm	25 mm sand
Vehicular driveway	200 – 300 mm	25 – 40 mm sand
Garage entrance	300 – 400 mm	40 mm sand

Retaining Walls

Design Principles

A retaining wall holds back earth. It is subject to lateral earth pressure, which increases with wall height. The lateral soil pressure is approximately:

P = 0.5 × γ × H² × Ka

Where:

γ = unit weight of soil (approximately 18 kN/m³ for saturated soil)

H = wall height (m)

Ka = active earth pressure coefficient (approximately 0.33 for granular soil)

Example: For a 1.2 m high wall:

P = 0.5 × 18 × 1.2² × 0.33 = 4.28 kN/m

This pressure must be counterbalanced by the weight of the wall and the friction at the base.

Types of Retaining Walls

Type	Typical Maximum Height	Material	Characteristics
Dry-stacked concrete block wall	1.0 – 1.2 m	Modular blocks	Dry-stacked, setback from vertical
Concrete block wall with geogrid	2.0 – 3.0 m	Blocks + geogrid	Soil reinforcement
Dry stone wall	1.0 – 1.5 m	Natural stone	Natural drainage
Cast-in-place concrete wall	3.0 m and above	Reinforced concrete	Requires engineering calculations

Retaining Wall Drainage

Drainage is critical for the stability of a retaining wall. Water accumulating behind the wall increases hydrostatic pressure and can cause failure.

Drainage components:

French drain (100 mm perforated pipe) at the base of the wall, wrapped in geotextile.

Drainage stone (20–40 mm) extending 300 mm behind the wall.

Weep holes every 1.2 m if the wall is cast-in-place concrete.

Geotextile to prevent soil from clogging the drainage stone.

Drain slope: minimum 1% (1 cm per metre) toward the discharge point.

Geogrid Reinforcement

For walls over 1.2 m, geogrids (synthetic mesh) are used to anchor the wall into the soil. The geogrid is placed horizontally between block courses and extends back a distance of at least 60% of the wall height.

Example: For a 2 m wall, the geogrid must extend 1.2 m behind the wall.

Slabs and Pavers: Installation and Finishing

Paver Installation on a Sand Bed

Complete procedure:

79.Excavation: remove organic soil to the required depth (see thickness table).

80.Soil compaction: run a vibrating plate compactor over the natural soil.

81.Geotextile placement: cover the excavated soil to prevent fine particles from migrating upward.

82.Crushed stone placement: spread in layers of 150 mm maximum, compacting each layer.

83.Levelling: check the slope (1 to 2% for water drainage).

84.Sand bed placement: spread 25 mm of sand, level with straightedges and screed guides.

85.Paver installation: start from a corner, follow the chosen pattern (running bond, herringbone, basketweave).

86.Final compaction: run the vibrating plate with a protective pad.

87.Joint filling: sweep fine sand into the joints, re-compact, repeat.

Drainage slope: minimum 1.5% (1.5 cm per metre) for paved surfaces, 2% for slab surfaces.

Edge Restraints

Perimeter pavers must be restrained to prevent lateral movement. The following are used:

Concrete curbs cast on a concrete footing.

Steel or aluminum edging (paver edging) secured to the ground with stakes.

Edge pavers set in mortar.

Rule: any paved surface larger than 10 m² must have a perimeter restraint on at least two adjacent sides.

Slab Installation on Mortar

For large-format slabs or high-traffic areas, slabs are set on a mortar bed (1 part cement to 4 parts sand). The mortar is spread to a thickness of 25 to 40 mm, the slabs are placed and adjusted with a spirit level, and the joints are filled with mortar or polymeric sand.

Stairs and Steps

Calculating Step Dimensions

The relationship between the tread (step depth) and the riser (step height) must follow the formula:

2 × Riser + Tread = 600 to 650 mm

Example: For a riser of 150 mm:

2 × 150 + Tread = 620

Tread = 620 – 300 = 320 mm

Comfortable values:

Riser: 140 – 180 mm

Tread: 280 – 350 mm

Building a Block or Slab Stair

108.Excavate the area and compact the soil.

109.Concrete footing beneath the first step (foundation).

110.Install blocks or step slabs, starting from the bottom.

111.Level each step (1% slope toward the front for drainage).

112.Fill hollow blocks with aggregate or concrete.

113.Finish: cap slabs set in mortar.

Minimum width: 1.0 m for a residential landscape stair, 1.2 m for a public stair.

Quantity Calculations

Calculating Concrete Volume

Volume (m³) = Length (m) × Width (m) × Thickness (m)

Example: A footing 8 m long, 0.5 m wide, and 0.2 m thick:

V = 8 × 0.5 × 0.2 = 0.8 m³

Add 10% for waste: 0.8 × 1.1 = 0.88 m³.

Calculating the Number of Pavers

Number of pavers = Total area (m²) ÷ Area of one paver (m²)

Example: For a 24 m² patio with 200 × 100 mm pavers (0.02 m²):

Number = 24 ÷ 0.02 = 1,200 pavers

Add 5 to 10% for breakage and cuts: 1,200 × 1.08 = 1,296 pavers.

Calculating Aggregate Volume

Volume (m³) = Area (m²) × Thickness (m)

Example: For a 40 m² driveway with 200 mm of crushed stone:

V = 40 × 0.2 = 8 m³

Add 15% for compaction (the material settles): 8 × 1.15 = 9.2 m³.

Applicable Codes and Standards

Canadian Electrical Code, Part I (CE Code)

This code applies to outdoor electrical installations: landscape lighting, charging stations, fountain pumps. Key rules to know:

Rule 8-200: Calculation of electrical demand for residential installations.

Rule 12-012: Burial of conductors — minimum depth of 600 mm for outdoor lighting circuits under a driveway, 450 mm under a lawn.

Rule 36-100: Clearances of conductors above ground.

Burial depths (Rule 12-012):

Location	Minimum Depth
Under a driveway or parking area	600 mm
Under a lawn or garden	450 mm
Under a foundation	600 mm

CSA B149.1 — Natural Gas and Propane Installation Code

This code applies to gas installations for outdoor fireplaces, fixed barbecues, and gas lamps. Key points:

Article 4.2.1: Piping must be made of approved materials (steel, copper, polyethylene for burial).

Article 6.3.1: Minimum burial depth of 400 mm for gas piping.

Article 6.4.1: Clearance of vents and terminations — minimum 300 mm from an openable window or door.

Other Relevant Standards

CSA A23.1: Concrete — materials and methods of construction.

CSA A23.2: Test methods for concrete.

CSA S304: Design of masonry structures (for load-bearing walls).

CSA Z614: Play spaces and equipment (for adjacent play areas).

Compaction Techniques

Soil and Aggregate Compaction

Compaction increases the density of a material by reducing voids. The following equipment is used:

Vibrating plate: for flat surfaces (sand, gravel, pavers).

Tamping rammer: for confined areas and trenches.

Roller compactor: for large areas.

Compaction test: the modified Proctor test determines the maximum density of a soil. For landscape construction, 95% of modified Proctor density is typically required for foundations.

Number of passes: typically 4 to 6 passes of a vibrating plate for a 150 mm layer of aggregate.

Common Compaction Errors

Compacting a layer that is too thick (> 150 mm): the bottom does not compact.

Compacting material that is too wet or too dry: maximum density is not achieved.

Failing to compact the natural soil before placing the aggregate.

Compacting pavers before filling the joints: the pavers shift.

Joints and Their Maintenance

Types of Paver Joints

Type	Material	Application	Lifespan
Joint sand	Fine sand (0–2 mm)	Pedestrian walkways	1 – 2 years
Polymeric sand	Sand + polymers	Driveways and patios	5 – 10 years
Mortar	Cement + sand	Slabs on mortar	20 years +

Polymeric sand hardens when moistened, creating a rigid joint that resists washing out and weed growth. It must be applied in dry weather and activated with a fine mist of water.

Caution: polymeric sand should not be used for joints wider than 10 mm, as it will not polymerize properly.

Safety Considerations

Job Site Safety

Personal protective equipment (PPE): hard hat, gloves, safety glasses, steel-toed boots, hearing protection.

Manual lifting: use your legs, do not lift more than 23 kg without mechanical assistance.

Trenches: any trench deeper than 1.2 m must be shored or sloped.

Concrete: fresh concrete is caustic — wear waterproof gloves and wash immediately upon contact.

Structural Safety

Never build a retaining wall over 1.2 m without engineering calculations.

Verify wall stability before removing shoring.

Mark work areas near overhead power lines (minimum distance of 3 m for lines under 750 V).

Pitfalls to Avoid

178.Forgetting the drainage slope: a perfectly flat surface retains water, causing frost damage and paver deterioration. Always provide a 1.5 to 2% slope.

179.Compacting a layer that is too thick: each aggregate layer must not exceed 150 mm before compaction.

180.Neglecting the geotextile: without it, fine soil particles migrate up into the aggregate, reducing bearing capacity and causing settlement.

181.Using construction sand for jointing: coarse sand does not penetrate joints well and washes out quickly.

182.Installing pavers on frozen ground: thawing will cause uneven settlement.

183.Ignoring frost depth for footings: a footing that is too shallow will be lifted by frost.

184.Not setting wall blocks back: block walls must have a setback of approximately 10 to 15 mm per course (5 to 10° inclination).

185.Forgetting weep holes in concrete retaining walls: water accumulates and hydrostatic pressure breaks the wall.

186.Calculating quantities without adding waste: always add 5 to 10% for pavers, 10% for concrete, 15% for aggregate.

187.Confusing bearing capacity and concrete strength: these are two distinct concepts — bearing capacity relates to the soil, strength relates to the concrete.

Summary

Soil bearing capacity determines foundation dimensions; clay and organic soils have the lowest bearing capacity.

Frost is the primary cause of failure: excavate below the frost line for load-bearing structures, use non-frost-susceptible materials, and ensure drainage.

Foundations consist of compacted soil, geotextile, crushed stone compacted in 150 mm layers, and a setting bed.

Retaining walls over 1.2 m require geogrid reinforcement or engineering calculations; drainage is mandatory.

Stairs must follow the formula 2 × riser + tread = 600 to 650 mm.

Drainage slopes are 1.5 to 2% for paved surfaces.

Key codes are the Canadian Electrical Code (Part I, Rule 12-012 for burial depths) and CSA B149.1 for gas.

Quantity calculations must include waste percentages: 5–10% pavers, 10% concrete, 15% aggregate.

Compaction must achieve 95% of modified Proctor density, in layers of 150 mm maximum.

Safety requires PPE, compliance with trench depths, and caution near power lines.

Exam preparation: review the thickness and bearing capacity tables, memorize the calculation formulas (earth pressure, step dimensions, volume), and practice solving quantity problems under timed conditions. Exam questions often focus on identifying procedural errors and quickly calculating materials.