Demolition, Removal, and Salvage Operations

Demolition, Removal, and Salvage Operations

Chapter Introduction

Demolition, removal, and salvage constitute a critical phase in the life cycle of a construction project. For the Construction Craft Worker, this stage requires a thorough understanding of structural principles, risks associated with existing materials, and sorting and recovery procedures. This chapter covers all the knowledge required for the Red Seal exam, including demolition methods, volume and load calculations, hazardous materials management, and applicable Canadian standards.

Demolition is not just about "tearing everything down." It involves a logical sequence, pre-work verifications, and precise knowledge of loads, support points, and fall paths. A calculation error or an omission in utility verification can result in serious injuries, property damage, or legal action.

Planning and Preparation of the Demolition Site

Preliminary Building Assessment

Before any demolition activity, a complete structural assessment must be carried out. This assessment determines the type of construction (wood frame, reinforced concrete, steel, masonry), the condition of load-bearing elements, and the presence of hazardous materials.

Essential documents to consult include:

The Canadian Electrical Code, Part I (C22.1-21) requires that all electrical installations be de-energized and locked out before demolition work begins. The lockout/tagout procedure must comply with CSA Z460-13 (R2022) "Control of Hazardous Energy - Lockout and Other Methods."

Demolition Sequence: Top-Down

The fundamental rule of manual or mechanical demolition is to proceed from the top down. This sequence prevents premature collapse of load-bearing walls and allows for progressive control of debris.

Typical order of intervention:

Each floor must be completely cleared before moving to the floor below. Debris must never accumulate on a floor beyond the calculated allowable load.

Calculating Allowable Floor Load

You must be able to estimate the load that an existing floor can support. The allowable load (in kN/m²) is calculated from the resistance of beams and joists, taking into account the safety factor.

Basic formula for a simply supported beam:

Allowable load (w) = (8 × M_r) / L²

Where:

Calculation example:

A 200 mm × 300 mm wood beam with an M_r of 45 kN·m and a span of 4.5 m:

w = (8 × 45) / (4.5)² = 360 / 20.25 = 17.78 kN/m

If the spacing between beams is 0.6 m, the allowable floor load is:

17.78 / 0.6 = 29.6 kN/m²

Reference table — Approximate linear loads of construction materials:

Exam trap: Do not confuse density (kg/m³) with load (kN/m³). Multiply the density by gravitational acceleration (9.81 m/s²) to obtain the load in kN/m³.

Demolition Methods

Manual Demolition

Manual demolition uses portable tools (jackhammers, sledgehammers, pry bars, chisels). It is preferred for:

Safety requirements:

Mechanical Demolition

Mechanical equipment includes:

Equipment selection depends on building height, required reach, and the load-bearing capacity of the supporting ground. A 30-tonne excavator with a 15 m boom can demolish a 3-storey building without climbing onto the debris.

Comparison table — Demolition methods:

Demolition by Implosion

Implosion is a specialized technique that uses strategically placed explosives to cause the building to collapse onto itself. This method is governed by the Explosives Regulations (SOR/2013-211) of Natural Resources Canada.

Key requirements:

The Construction Craft Worker is generally not responsible for designing the implosion, but you must understand the basic principles to coordinate the site and ensure perimeter safety.

Hazardous Materials Management

Asbestos

Asbestos is the most frequently encountered hazardous material during demolitions. It was used extensively in Canada until the late 1980s in:

The Canada Occupational Health and Safety Regulations under Part II of the Canada Labour Code requires an exposure assessment before work begins. CSA Z94.4-18 "Selection, Use, and Care of Respirators" specifies requirements for respirators.

Mandatory procedures for asbestos removal:

Occupational Exposure Limit (OEL): 0.1 fibres/cm³ over 8 hours (according to the Canada Occupational Health and Safety Regulations).

Other Hazardous Materials

Exam trap: Crystalline silica is not a "hazardous waste" in the regulatory sense, but it presents a major occupational exposure risk. Dust control measures (source capture, water spray) are mandatory when cutting concrete or masonry.

Material Salvage and Sorting

Salvage Principles

Salvage involves carefully removing reusable materials before demolition. This practice reduces disposal costs and generates revenue. Commonly salvaged materials include:

Traceability requirement: Recovered structural elements (beams, columns) must be certified by an engineer before reuse in a new project. CSA S16-19 "Design of Steel Structures" specifies evaluation criteria for used steel elements.

Sorting Demolition Debris

Sorting can be done on-site (primary sorting) or at a processing facility. Standard sorting categories are:

Calculating debris volume:

The volume of debris after demolition is generally greater than the initial building volume due to bulking. The bulking factor varies by material:

Calculation example:

A 500 m³ building of reinforced concrete will produce:

500 m³ × 1.4 = 700 m³ of bulked debris

If a 12 m³ container is used, you will need:

700 / 12 = 58.3 → 59 containers (round up to the next whole number)

Exam trap: The bulking factor applies to initial volume, not mass. Mass remains constant (conservation of mass applies), only volume changes.

Safety and Protection of Adjacent Structures

Establishing the Safety Perimeter

The safety perimeter must be established at a minimum distance equal to the height of the building being demolished, plus 1.5 m. For a 10 m high building, the perimeter is 11.5 m.

Perimeter requirements:

Protection of Adjacent Structures

Before work begins, a photographic inspection of neighbouring buildings must be carried out to document their condition. This inspection serves as a reference in the event of a damage claim.

Typical protection measures include:

Dust Management

Demolition dust poses health risks to workers and occupants of adjacent buildings. Control measures include:

Regulatory requirement: Dust emissions must comply with provincial environmental regulations (although the Red Seal exam focuses on national standards, knowledge of control principles is essential).

Load and Volume Calculations for Removal

Calculating Debris Mass

The total mass of debris is calculated by multiplying the initial volume by the material density, then applying the bulking factor for transport volume.

Formula:

Mass (kg) = Initial volume (m³) × Density (kg/m³)

Example:

Demolition of a plain concrete wall 20 m long, 3 m high, and 0.3 m thick.

Volume = 20 × 3 × 0.3 = 18 m³

Mass = 18 m³ × 2,300 kg/m³ = 41,400 kg = 41.4 tonnes

If a dump truck has a capacity of 15 tonnes, you will need:

41.4 / 15 = 2.76 → 3 trucks (round up to the next whole number)

Calculating the Number of Containers

The number of containers required depends on the bulked volume and the container capacity.

Formula:

Number of containers = (Initial volume × Bulking factor) / Container capacity

Table of standard container capacities:

Exam trap: Never exceed the container's load capacity, even if the volume is not full. A 12 m³ container filled with concrete would weigh 12 × 1.4 × 2,300 = 38,640 kg, or nearly 39 tonnes — far above the 8-tonne capacity. The volume must be limited accordingly.

Applicable Standards and Regulations

National Standards of Canada

Federal Regulations

Key requirement of the Transportation of Dangerous Goods Regulations: Asbestos waste must be transported in sealed containers, identified with Class 9 (miscellaneous dangerous goods), and accompanied by a shipping document.

Utility Shut-Off Procedures

Shut-Off Sequence

Utility shut-off must be carried out in a specific order to avoid fire, explosion, or electrocution risks:

CSA B149.1 requirement (Article 4.16): Before demolishing a building, the gas supplier must be notified and the service line must be shut off and sealed at the main shut-off valve. It is prohibited to cut a gas line without written authorization from the supplier.

Verifying Absence of Voltage

After the electricity is shut off, a verification of absence of voltage must be performed using a calibrated voltage detector. This verification is mandatory before any work on electrical circuits.

Procedure:

Pitfalls to Avoid

Summary

Demolition, removal, and salvage are high-risk operations that require rigorous planning and methodical execution. Key points to remember for the Red Seal exam:

The Red Seal certified Construction Craft Worker must not only execute the work but also understand the underlying engineering principles, apply national standards, and ensure the safety of all personnel. Mastering this chapter prepares you to answer exam questions on the technical, regulatory, and practical aspects of demolition.

Self-Assessment Questions

a) 1.0 – 1.1

b) 1.3 – 1.5

c) 1.8 – 2.0

d) 2.5 – 3.0

a) 0.01 fibres/cm³

b) 0.1 fibres/cm³

c) 1.0 fibres/cm³

d) 10 fibres/cm³

a) 8 m

b) 9.5 m

c) 10 m

d) 12 m

a) CSA S850-12

b) CSA Z460-13

c) CSA Z94.4-18

d) CSA B167-16

a) 9.4 tonnes

b) 18.8 tonnes

c) 23.4 tonnes

d) 28.1 tonnes

Answers: 1-b, 2-b, 3-b (8 + 1.5 = 9.5 m), 4-b, 5-c (Volume = 15 × 2.5 × 0.25 = 9.375 m³; Mass = 9.375 × 2,500 = 23,437.5 kg ≈ 23.4 tonnes)