Prefabricated formwork systems on construction projects

This resource does not replace the Occupational Health and Safety Act (OHSA) and its regulations and should not be used as or considered legal advice. Health and safety inspectors apply these laws based on the facts they find in the workplace.

Overview

Inspectors of the Ministry of Labour, Immigration, Training and Skills Development have investigated multiple failures involving slab formwork in the high-rise and mid-rise building construction sector. The formwork system used in all these incidents was made of prefabricated metal components (aluminum, steel, or a combination of both). In all investigated cases workers were working on the deck to install or strip the formwork panels. In most of the cases the main longitudinal beam got dislodged causing the panels to drop and ultimately the workers fell off the deck. Deviations from the manufacturer’s instructions were made and were not reviewed and approved by an engineer. This guidance is mainly for the employer most responsible for the formwork system on project (“formwork employer”). It does not limit the responsibility of other workplace parties on the project under the OHSA and its regulations.

Highlights of some regulatory requirements

Section 87 of O. Reg. 213/91 outlines the design and the set-up requirements for formwork, falsework, and reshoring and includes the following key requirements:

“Formwork, falsework and re-shoring shall be designed, constructed, supported and braced so that they are capable of withstanding all loads and forces likely to be applied to them, without exceeding the allowable working loads established for any component of the structure; and without causing uplift, sliding, overturning or lateral displacement of the system.”

The regulation also outlines that, “no formwork, falsework or re-shoring shall be loaded in excess of the load that it is designed and constructed to bear.”

It also requires that the allowable working load of the formwork, falsework or re-shoring be established by an engineer in accordance with good engineering practice, or by testing the principal components in a specified manner. In the latter case, the testing results must be verified and certified by an engineer and made available to an inspector upon request.

Section 92 of O. Reg. 213/91 outlines specific details to be identified in the design drawings by an engineer for the formwork, falsework, or re-shoring, for both manufactured and non-manufactured systems:

• Whether the system is manufactured or non-manufactured, the drawings must:
  • Show the design loads for the structure and detail the bracing and external ties required to adequately support the design loads.
  • If the structure is a unitized modular formwork or falsework structure intended to be lifted or moved as a unit, show the attachment points for rigging and hoisting.
  • Set out the erection instructions that are specified by the manufacturer or by the engineer.
• If a manufactured system is used, the design drawings must identify its components.
• If non-manufactured system components are used, the design drawings must show the size, grade, and specifications of the non-manufactured system components.

Design, construction and bracing of the formwork

Following the design drawings of the engineer who designed the system is instrumental to comply with the requirements of sections 87 and 92 of O. Reg. 213/91, and to ensure a safe work environment for the workers installing the system or working in its vicinity.

It is to be emphasized that the “notes” on the design drawings are an integral part of the drawing:

• when a procedure is set out in the “notes”, it must be followed
• when the “notes” indicate that a detail must be “designed by others,” the design drawings of that detail must be available on the project and followed when the system is built

Prefabricated formwork systems: one prefabricated system or mixed systems

In prefabricated formwork systems, manufacturer instructions are as important as design engineer’s drawings. When using only one system, manufacturers instructions must be followed.

Where there is any deviation in the use of the system from the manufacturer’s instructions, the use should be designed and approved by an engineer.

When prefabricated formwork systems are used and mixed components from different manufacturers observed, this should be shown on the design drawings of the engineer.

Should the employer choose to use more than one manufacturer for prefabricated components, the overall system is to be approved by an engineer.

When prefabricated components are sourced by more than one manufacturer, subject to the manufacturers’ instructions not prohibiting such usage, an engineer must review the overall design and approve of it in writing, along with outlining the methodology for its set up, including the revised bracing as needed and dictated by the site conditions.

Inspection of formwork and falsework before placement of concrete

Section 89 of O. Reg. 213/91 requires that before the placement of concrete, certain formwork and falsework be inspected by an engineer or by a competent worker designated in writing by the engineer. It also requires the person carrying out the inspection to state in writing whether the formwork and falsework is installed or erected in accordance with the design drawings for it.

The constructor is required to keep the design drawings and the inspection written statements on the project while the formwork or the falsework is in use.

Competency, training, and identification of system components

The following are essential to achieving a safe work environment when installing or dismantling formwork, falsework, and reshoring:

• adequate training for workers involved
• proper identification of the sources of equipment being used
• use of the equipment in accordance with its manufacturer’s instructions
• clear distribution of roles and responsibilities

Supervision and training

It is imperative to know who oversees the formwork, falsework, and re-shoring on the project. This person is often referred to as the formwork supervisor or foreman.

The supervisor or foreman of the formwork employer must always be a competent person. A “competent person” is defined in the Occupational Health and Safety Act to mean a person who:

• is qualified because of knowledge, training and experience to organize the work and its performance
• is familiar with this act and the regulations that apply to the work
• has knowledge of any potential or actual danger to health or safety in the workplace

A formwork supervisor or foreman should, be, at a minimum:

• adequately trained in reading and understanding the design drawings and manufacturers’ instructions for the equipment and materials in use
• capable of explaining to the workers engaged in the operation what needs to be done and procedure to be followed in setting up or dismantling the formwork, falsework, or reshoring
• familiar with the Occupational Health and Safety Act and the regulations that apply to the work
• has knowledge of any potential or actual danger to health or safety in the workplace

Inspection

It is important to clearly identify the person who will carry out the inspection prior to pouring the concrete – this will either be an engineer, or a competent worker designated in writing by the engineer.

Identifying and using components

The formwork employer or their representative must be capable of identifying the source of the formwork and falsework components — whether they were supplied by one manufacturer, or more than one manufacturer.

As part of the formwork employer’s obligations under Sections 25(1)(c) and 25(2)(a) of OHSA, the formwork employer or their representative must ensure that:

• the manufacturers’ instructions are on the project, available to the formwork workers —this applies also to the formwork, falsework, and re-shoring engineer’s drawings
• any alteration or deviation from the engineer’s drawings to the formwork, falsework or re-shoring components is accompanied by written approval from an engineer that is kept available on the project
• any modification to the prefabricated components has been inspected and approved in writing by the manufacturer (or by an engineer) when all the components are issued by the same manufacturer
• in instances of hybrid systems (in other words, when the components are issued by different manufacturers), modifications to the prefabricated components are inspected and approved by the engineer who designed the system the components’ labels reflect the real manufacturer of the components
• the source of the equipment is traceable so that maintenance is verifiable
• before the placement of concrete, formwork and falsework are inspected by an engineer or by a competent worker designated in writing by an engineer

The formwork employer must ensure all records are on the project and are provided to the constructor. The formwork employer must be able to identify the source of the formwork, falsework, and re-shoring components whether they are using: one supplier, more than one supplier, purchased components, etc.

Constructor, employer, and supplier duties under OHSA

Sections 23, 25 and subsection 31(1) of the Occupational Health and Safety Act. R.S.O. 1990, c. 0.1 (OHSA) outline the respective duties of constructors, employers, and suppliers to comply with health and safety requirements.