Masonry and Structural Support Systems

Chapter Introduction

This chapter covers the essential knowledge related to masonry and structural support systems that every Red Seal Construction Craft Worker must master for the Red Seal exam. You will find the fundamental principles, basic calculations, safety rules, and applicable Canadian standards. Mastering this content is crucial, as masonry work and structural supports represent a significant portion of daily tasks on construction sites across Canada.

1. Fundamentals of Masonry

1.1 Definition and Scope

Masonry is the art and technique of assembling units of materials (bricks, concrete blocks, natural or artificial stones) using mortar or other binders to form load-bearing or non-load-bearing structures. As a construction craft worker, you will be called upon to prepare surfaces, erect scaffolding, transport materials, and assist qualified masons.

1.2 Types of Masonry Units

Type of Unit	Common Dimensions (mm)	Approximate Mass	Typical Use
Clay brick	190 × 90 × 57	2.5 – 3.5 kg	Exterior walls, partitions
Concrete block (CMU)	400 × 200 × 200	18 – 22 kg	Load-bearing walls, foundations
Natural stone	Variable	Variable	Veneers, decorative walls
Lightweight concrete block	400 × 200 × 200	12 – 15 kg	Interior partitions, non-load-bearing walls
Refractory brick	230 × 114 × 76	3.5 – 4.5 kg	Chimneys, industrial furnaces

1.3 Mortar: Composition and Types

Mortar is a mixture of cement, lime, sand, and water. The proportions vary depending on the type of mortar required. The National Building Code of Canada (NBCC) recognizes five types of mortar, designated by the letters S, N, M, O, and K.

Type	Portland Cement	Lime	Sand	Compressive Strength (MPa)	Recommended Use
M	1	0.25	3.5	17.2	Underground structures, heavy load-bearing walls
S	1	0.5	4.5	12.4	Load-bearing walls, retaining walls
N	1	1	6	5.2	Exterior walls above grade
O	1	2	9	2.4	Interior non-load-bearing walls
K	1	3	12	0.5	Repairs, expansion joints

Golden rule: Type S mortar is the most commonly used for load-bearing walls in Canadian climates due to its balance between strength and flexibility.

1.4 Calculating Mortar Volume

To estimate the volume of mortar required, use the following formula:

Mortar volume (m³) = Total wall volume (m³) − Volume of units (m³)

Example: For a 10 m × 3 m × 0.2 m wall made of concrete blocks:

Total volume = 10 × 3 × 0.2 = 6 m³

Volume of blocks (approximately 75% of total volume) = 4.5 m³

Mortar volume = 6 − 4.5 = 1.5 m³

Exam tip: As a general rule, mortar represents approximately 25 to 30% of the total volume of a masonry wall.

2. Structural Support Systems

2.1 Fundamental Concepts

A structural support system is the set of elements that transmit loads (dead, live, wind, seismic) from a structure to the ground. The main elements are:

Foundations (footings, raft foundations, piles)

Load-bearing walls (masonry, reinforced concrete)

Columns and posts

Beams and lintels

Floors and roofs

2.2 Loads and Basic Calculations

Dead load (D) is the self-weight of the structure and all fixed elements. Live load (L) includes occupants, furniture, equipment, and snow or wind loads.

Fundamental load combination (limit states method):

Load factor = 1.25 × D + 1.5 × L

Example: For a floor with D = 3.0 kN/m² and L = 2.4 kN/m²:

Design load = 1.25 × 3.0 + 1.5 × 2.4 = 3.75 + 3.6 = 7.35 kN/m²

2.3 Lintels and Precast Lintels

A lintel is a structural element placed above an opening (door, window) to support the load above. Lintels can be made of:

Reinforced concrete (cast-in-place or precast)

Steel (angles, joists)

Glulam timber

Minimum bearing rule: A lintel must bear on a support of at least 150 mm on each side of the opening, in accordance with the NBCC.

2.4 Anchors and Ties

Masonry walls must be anchored to the structural frame to resist lateral loads (wind, seismic). Typical anchors include:

Anchor rods (steel bars embedded in mortar)

Wall ties (Z-shaped or L-shaped metal ties)

Brackets and fixing plates

Maximum anchor spacing: According to the NBCC, anchors must be spaced no more than 900 mm horizontally and vertically, with an anchor within 300 mm of each opening.

3. Scaffolding and Work Platforms

3.1 Types of Scaffolding

Type	Maximum Height	Allowable Load	Use
Frame scaffolding (tube)	30 m (with engineer)	2.4 kN/m²	General masonry work
Rolling scaffolding	3 × minimum base	1.2 kN/m²	Interior work, maintenance
Suspended scaffolding	Variable	1.5 kN/m²	Facades, window cleaning
Aerial work platform	Variable	Variable	Occasional work at height

3.2 Essential Safety Rules

The maximum load of a scaffold must be clearly posted.

Scaffolds must be inspected before each use and after any modification.

Guardrails (top rail, intermediate rail, toe board) are mandatory above 1.2 m in height.

Access to the scaffold must be via integrated ladders or stairs, never by climbing the frames themselves.

Scaffolds must be tied to the building every 6 m horizontally and every 4 m vertically.

Common trap: Never overload a scaffold with stacked materials. Materials must be evenly distributed and walkways must remain clear.

3.3 Stability Calculation

The stability of a scaffold depends on the ratio between its height and the width of its base. The maximum ratio is 3:1 for a free-standing (untied) scaffold. Beyond that, the scaffold must be tied or stabilized.

Verification formula:

Height-to-width ratio = Total height ÷ Base width

Example: A 9 m high scaffold with a 2.5 m base:

Ratio = 9 ÷ 2.5 = 3.6 → Exceeded → Tying is mandatory.

4. Concrete and Formwork

4.1 Concrete Properties

Concrete is a mixture of cement, aggregates (sand and stone), water, and admixtures. Its strength is expressed in megapascals (MPa) at 28 days.

Concrete Class	28-Day Strength (MPa)	Typical Use
Lean concrete	10 – 15	Footings, base course
Regular concrete	20 – 25	Slabs, foundation walls
Structural concrete	30 – 35	Columns, beams, floors
High-performance concrete	40+	Special structures, bridges

4.2 Formwork: Principles and Calculations

Formwork is the temporary mold that gives shape to fresh concrete. It must be:

Watertight (to prevent loss of cement paste)

Rigid (to prevent deformation)

Removable (for stripping)

Fresh concrete pressure on formwork:

P = ρ × g × h

Where:

P = pressure (Pa)

ρ = density of concrete (≈ 2400 kg/m³)

g = gravitational acceleration (9.81 m/s²)

h = height of poured concrete (m)

Example: For a pour height of 1.5 m:

P = 2400 × 9.81 × 1.5 = 35,316 Pa ≈ 35.3 kPa

Exam tip: Concrete pressure increases linearly with pour height. To reduce pressure on the formwork, pour in successive layers.

4.3 Curing

Curing is the process of maintaining the moisture and temperature of concrete after pouring to allow complete cement hydration. It must begin as soon as the concrete surface is sufficiently hard and continue for at least 7 days for ordinary concrete.

Curing methods:

Continuous or periodic watering

Wet burlap

Curing membranes (chemical compounds)

Polyethylene sheets

5. Applicable Canadian Standards and Codes

5.1 National Building Code of Canada (NBCC)

The NBCC is the reference document for the design and construction of buildings in Canada. The relevant sections for masonry and structural supports include:

Part 4: Structural design (loads, resistance)

Part 5: Separation of elements (moisture protection)

Part 9: Small buildings (housing)

5.2 CSA A371 — Masonry

The CSA A371 standard "Masonry Construction" establishes requirements for material selection, execution, and quality control of masonry work.

Key points:

Dimensional tolerances: ± 3 mm for mortar joints

Minimum joint thickness: 10 mm (bed joints)

Reinforcement required in reinforced masonry walls

5.3 CSA A23.1/A23.2 — Concrete

The CSA A23.1 standard "Concrete: Constituents and Execution of Work" and CSA A23.2 "Test Methods for Concrete" are the references for all concrete work in Canada.

5.4 CSA S16 — Structural Steel

The CSA S16 standard "Design of Steel Structures" applies to steel elements used as structural supports.

5.5 Wood Products Regulations

For wood support elements, consult CSA O86 "Engineering Design in Wood."

6. Safe Work Procedures

6.1 Lifting and Handling Materials

Use safe lifting techniques: straight back, bent legs, load close to the body.

Concrete blocks must be transported using block tongs or handling gloves.

Never exceed the load capacity of lifting equipment (hoists, cranes).

6.2 Working at Heights

Wear a safety harness attached to a certified anchor point when working more than 3 m above grade (according to federal and provincial regulations).

Guardrails must be installed on all open edges of work platforms.

Establish a ground safety perimeter to prevent injuries from falling objects.

6.3 Respiratory Protection

When cutting bricks or blocks, wear a dust mask (N95 minimum).

Dry cutting of materials containing crystalline silica requires higher respiratory protection (P100 or supplied-air respirator).

7. Quality Control and Inspections

7.1 Material Inspection on Delivery

Check that bricks and blocks have no cracks, chips, or excessive efflorescence.

Check the manufacturing date of cement (do not use cement older than 6 months).

Cement bags must be stored protected from moisture, on a raised platform.

7.2 Checking Alignment and Plumb

Use a spirit level and plumb bob to check the verticality of walls.

Plumb tolerance: ± 6 mm over 3 m of height (according to CSA A371).

Horizontal alignment tolerance: ± 10 mm over 10 m of length.

7.3 Compression Tests

Concrete cylinders must be sampled according to CSA A23.2.

Mortar prisms must be made and tested according to CSA A179.

8. Practical Site Calculations

8.1 Number of Blocks per Square Metre

Formula:

Number of blocks/m² = 1 ÷ (block length × block height)

Example: 400 mm × 200 mm block (0.4 m × 0.2 m):

Area of one block = 0.4 × 0.2 = 0.08 m²

Number of blocks/m² = 1 ÷ 0.08 = 12.5 blocks

Exam tip: Add 5 to 10% for waste and breakage when ordering materials.

8.2 Number of Bricks per Square Metre

For a standard 190 mm × 57 mm brick with a 10 mm joint:

Effective dimensions: 200 mm × 67 mm (0.2 m × 0.067 m)

Area = 0.2 × 0.067 = 0.0134 m²

Number of bricks/m² = 1 ÷ 0.0134 ≈ 75 bricks

8.3 Concrete Volume for a Footing

Formula:

Volume (m³) = Length × Width × Height

Example: Footing of 12 m × 0.6 m × 0.3 m:

Volume = 12 × 0.6 × 0.3 = 2.16 m³

Add 5% for waste: 2.16 × 1.05 = 2.27 m³

9. Demolition and Masonry Repair

9.1 Demolition Techniques

Manual demolition: using sledgehammers, chisels, and pry bars. Suitable for small areas.

Mechanical demolition: using jackhammers, hydraulic breakers. Suitable for large areas.

Diamond cutting: for precise cuts in walls.

Safety: Always check for the presence of electrical conduits, gas, or water lines before starting demolition. Use a metal detector and consult the plans.

9.2 Mortar Joint Repair (Repointing)

Repointing involves replacing deteriorated mortar in the joints of a masonry wall.

Procedure:

168.Remove deteriorated mortar to a depth of 15 to 20 mm.

169.Clean the joint using a wire brush and water.

170.Dampen the joint before applying new mortar.

171.Apply mortar in successive layers of 10 mm maximum.

172.Smooth the joint with an appropriate tool (jointing iron).

10. Pitfalls to Avoid

175.Confusing mortar types: Type M is the strongest, but Type S is the most versatile. Do not choose a stronger mortar than necessary — this can cause cracking in the bricks.

176.Neglecting lintel bearing: Insufficient bearing (less than 150 mm) can lead to structural failure.

177.Forgetting anchors: Unanchored masonry walls are extremely vulnerable to lateral loads.

178.Overloading scaffolding: The posted maximum load is an absolute limit, not a suggestion.

179.Ignoring concrete curing: Un-cured concrete can lose up to 50% of its potential strength.

180.Using damaged materials: Cracked or chipped blocks compromise the integrity of the wall.

181.Incorrectly calculating quantities: Forgetting the waste factor (5–10%) can lead to costly delays.

182.Confusing units: Dimensions in millimetres and metres must be converted correctly in calculations.

183.Working without respiratory protection: Silica dust is a real and regulated hazard.

184.Not checking plans and specifications: Each project has specific requirements that take precedence over general practices.

11. Exam Tips

Memorize the mortar types (M, S, N, O, K) and their uses.

Master volume calculations (concrete, mortar, number of units).

Know the tolerances: plumb (± 6 mm/3 m), alignment (± 10 mm/10 m).

Remember the key standards: CSA A371 (masonry), CSA A23.1 (concrete), CSA S16 (steel).

Practice load combinations: 1.25 × D + 1.5 × L.

Understand fresh concrete pressure: P = ρ × g × h.

Pay attention to safety details: guardrails, harnesses, anchors.

Summary

Masonry involves assembling bricks, blocks, and stones with mortar. The five mortar types (M, S, N, O, K) have specific strengths and uses.

Structural support systems transmit loads to the ground. Load combinations use factors of 1.25 (dead) and 1.5 (live).

Lintels must have a minimum bearing of 150 mm on each side.

Scaffolding must respect a maximum height-to-width ratio of 3:1 without ties, and be inspected regularly.

Fresh concrete pressure on formwork is calculated with P = ρ × g × h (≈ 35 kPa for 1.5 m height).

Concrete curing must last at least 7 days to ensure 28-day strength.

The reference Canadian standards are the NBCC, CSA A371, CSA A23.1/A23.2, and CSA S16.

Construction tolerances are strict: ± 6 mm plumb over 3 m, ± 10 mm alignment over 10 m.

Quantity calculations must include a waste factor of 5 to 10%.

Safety is paramount: respiratory protection, harnesses, anchors, and equipment inspection.

Pitfalls to Avoid

Pitfall	Consequence	Prevention
Confusing mortar types	Cracks, structural failure	Memorize the table of types and uses
Insufficient lintel bearing	Collapse of the opening	Verify minimum 150 mm bearing
Forgetting wall anchors	Instability under lateral load	Respect maximum 900 mm spacing
Scaffold overload	Collapse, serious injuries	Respect posted load, distribute materials
Neglecting curing	Loss of concrete strength	Maintain moisture for 7 days minimum
Quantity calculations without waste	Material shortage, delays	Add 5–10% for waste
Ignoring tolerances	Non-compliance, inspection rejection	Check with level and plumb bob
Working without respiratory protection	Silicosis, lung disease	Wear N95 or P100 mask depending on task
Not checking plans	Costly errors	Always consult plans and specifications before starting
Confusing units of measurement	Calculation errors	Systematically convert to metres for volumes

This chapter provides you with the essential knowledge to succeed in the "Masonry and Structural Support Systems" section of the Red Seal exam. Review regularly, practice the calculations, and familiarize yourself with Canadian standards. Good luck with your preparation!

Masonry and Structural Support Systems