Category Archives: Code of Practice for Demolition of Buildings

Code of Practice for Demolition of Buildings – Steel Catchfan

Leave a reply
  • Steel Catchfan

The steel catchfans are considered as temporary cantilevered structures with steel framing extended from the building. The use of expansive anchor bolts in erecting the catchfan shall be avoided as far as practicable since the anchor bolt may be loosened by vibration generated during the demolition process. In the case when anchors are used, they shall be applied cautiously with extreme care; and not as a primary support. Extreme care shall be exercised in erecting and dismantling the catchfan to avoid the structural components from accidentally falling off. All the components of the steel catchfan shall be supported, and securely fastened to the lifting appliances or supporting structural element until the installation is completed. Catchfan may be constructed with components of prefabricated steel/metal scaffold. Such use is particularly compatible with metal scaffolds. The design and installation of catchfan using prefabricated metal scaffold components shall be in accordance with the manufacturer’s recommended criteria. As far as practicable, the components of the catchfan shall be prefabricated and fastened by bolt to minimise welding.

Code of Practice for Demolition of Buildings – Bamboo Catchfan

Leave a reply
  • Bamboo Catchfan

Typical Detail of Bamboo Catchfan is illustrated in Figure 3.3.

  • Framing

A bamboo catchfan shall be constructed with bamboo framing tied to the building and the scaffold. The supporting bamboo member shall be tied to the standards of both the outer and inner scaffolding layers at the desirable inclined angle extended into the building. The catchfan supports shall be anchored to the

building wall or other structural elements. The spacing between the supporting bamboo members shall be not less than the distance between the standards of the scaffold or not more than

1.3 m whichever is less. The supporting bamboo framing shall be anchored to the building wall or other structural elements with anchor bolts and steel wire ties of adequate strength. The spacing between the anchor shall be not more than 3 m. The supporting bamboo shall have an effective diameter of not less than 40 mm.

  • Decking

The Bamboo members which are tied to the supporting members to form the deck of the fan shall have diameter of not less than 40 mm. Bamboo shall be placed across the supporting members at not more than 200 mm centres. Tarpaulin, net and metal sheet or corrugated metal sheet shall be placed on the top of the fan to retain debris. The thickness of the metal sheet shall be 0.5 mm. The tarpaulin, net, and metal sheets shall be securely fastened to the bamboo.

Code of Practice for Demolition of Buildings – Catchfan

Leave a reply
  1. Catchfan
  • 3.4.1         Requirements

The design intention of the catchfans is to catch small pieces of building debris that passes through the protective screen and net, and the catchfans are not designed to collect large pieces of building debris which should have been collected by the protective screen or net. A small piece of debris could be disastrous after gaining enough kinetic energy through falling great heights. Thus, a catchfan shall be installed at a vertical distance of not more than 10 m below the working floor. A catchfan shall have a horizontal extension of 1.5 m from the exterior face of the scaffolding. The typical angle of inclination shall be 20o to 45o from the horizontal plane. Catchfans shall be used only as precautionary measures and shall not be used as temporary support for any anticipated loads.

Both bamboo catchfans and metal catchfans are acceptable provided that they are properly installed. Under the present craftsman’s techniques, bamboo catchfans can be applied to either bamboo scaffolds or metal scaffolds, but metal catchfans are allowed to be mounted on metal scaffolds only.

Code of Practice for Demolition of Buildings – Screen Covers

Leave a reply
  • Screen Covers
  • Requirements

Two layers of protective screen shall be placed over the scaffolds to completely enclose the building structure for retaining dust and small debris. Tarpaulin and heavy duty nets shall be used to cover the exterior face of the scaffold. Tarpaulin shall be placed over the net. The screen system shall satisfy the requirements under the Air Pollution Control (Construction Dust) Regulation administered by the Environmental Protection Department, where applicable.

  • Ties

The protective screens shall be secured to the scaffoldings at not more than 2 m intervals at both horizontal and vertical directions or the width of the net, whichever is less. The screens shall have a minimum overlapping width of 300 mm.

  • Nets
  • Materials and Installation

Heavy duty nets shall be relatively light weight and have good retaining capability for small debris. The material shall resist ultra-violet light deterioration. The nets shall be secured to the scaffold and at the catchfan so that debris can be retained and not deflected onto the ground.

The net shall meet the minimum requirements as listed in Table 3.3 or approved equivalent.

Table 3.3 Minimum Specification for Polyethylene Net

CriteriaMinimum Requirement
materialpolyethylene
string diameter1 mm
plys16
mesh grid opening20 mm
weight130 g/m2


  • Tarpaulin

Tarpaulin shall be light weight and constructed of fire retardant materials.

The fire retardant characteristic of the tarpaulin shall meet either one of the following requirements:

  • Class B material as specified in British Standard 5867;
    • Flame retardant test for certain items, light weight cloths methods, provided by the Fire Retardant Regulations for Protective Canvas for Construction, Japan Ministerial Ordinance of the Ministry of Home Affair; or
      • Any equivalent standard criteria or testing.

Code of Practice for Demolition of Buildings – Dismantling scaffolds

Leave a reply
  • Dismantling

Dismantling of the scaffolds shall coincide with the demolition progress. When the wall ties are disconnected due to the demolition of the building structure, the unsecured section of the scaffolds shall be removed accordingly. The unbraced sections shall not be higher than 2m from the nearest anchor.

Code of Practice for Demolition of Buildings – Metal Scaffold

Leave a reply
  • Metal Scaffold

The requirements of the Code of Practice for Metal Scaffolding Safety and the recommendations from manufacturer shall be followed.

Furthermore, as a minimum, the scaffold shall be able to support the live load imposed on three consecutive layers of work platform plus its own weight. Additional loading conditions, if any, shall be included in determining the allowable height for the scaffoldings. Tie to existing structure shall be in accordance with manufacturer’s recommendations.

Code of Practice for Demolition of Buildings – Bamboo Scaffold

Leave a reply
  • Bamboo Scaffold

The requirements of the Code of Practice for Bamboo Scaffolding Safety have to be complied with.

In addition, structural ties to the building structure shall be provided in accordance with manufacturer’s recommendations. Bamboo scaffold shall be tied to sound anchors at intervals of not more than 4m in both horizontal and vertical directions.

If the scaffold is higher than 15m, steel brackets anchored to the existing building structure or other support system shall be provided at interval of not more than 15m to support the scaffold.

Code of Practice for Demolition of Buildings – Scaffolding Construction and Work Platform Requirements

Leave a reply
  • Scaffolding Construction and Work Platform Requirements

The erection, dismantling and safety requirements of the work platforms and scaffold shall be in accordance with the Construction Sites (Safety) Regulations and the relevant codes of practice on scaffolding safety issued by the Labour Department. The works shall be carried out by trained workmen under the immediate supervision of a competent person.

Supports for the scaffolds should be of adequate strength to hold the vertical and lateral loads imposed on the scaffolds including the catchfans, work platforms, etc. In case when elevated supports are required to receive the weights of the scaffolds, be they the steel brackets and anchors fixed to the existing building or other kinds of supporting system, they shall be designed by a Registered Structural Engineer. Where working platforms are required to facilitate working at height, they shall be properly constructed and provided on the three consecutive lifts directly below the floor being demolished with toe boards provided at the outer edge. Periodic maintenance shall be performed to remove any debris accidentally falling out of the building and accumulated on the platforms.

Code of Practice for Demolition of Buildings – Scaffoldings

Leave a reply
  • Scaffoldings

Bamboo scaffolds or metal scaffolds shall be used for top down demolition projects. Both bamboo scaffolds and metal scaffolds are considered acceptable provided that they are erected according to the Construction Sites (Safety) Regulations and the codes of practices on scaffolding safety.

Code of Practice for Demolition of Buildings – Lighting

Leave a reply
  • Lighting

A system of temporary lighting shall be provided for the covered walkway and shall be maintained in good order. The average illuminance on the floor level of the covered walkway shall be within the range of 35 lux to 50 lux. The lighting shall be weather-proofed. A recommended lighting layout for typical covered walkway is the installation of luminaries complete with 18 W or 20 W 600 mm long tubular florescent lamps at 3 m spacing.