### The mechanics of scaffolding

Mr Chan explained the mechanics of scaffolding with reference to trigonometry.

### The function of bamboo scaffolding

The purpose of bamboo scaffolding is to enable the construction and renovation projects to be completed in safe and efficient ways.

### Methods to build hanging scaffolds

The methods to build hanging scaffolds have changed nowadays. In the past, skilled workers used two long bamboos to be the foundation of a scaffold. The skilled workers would screw a hole on the exterior wall of a building and fix one bamboo against another forming a vertical triangular base. Nowadays, workers would use steel rods to build this base and nobody would use bamboo to build the base anymore.

### Scaffold Grids

The size of one grid of a bamboo scaffold is not fixed. A grid is 2 feet x 2.5 feet, which normally fits the body height of a Chinese workman from his shoulder to his bottom. Such size utilizes the elastic strength of a bamboo the best.

### Bamboo

Bamboos for scaffolding are usually imported from Guangxi. Normally each piece is roughly of 7 metres long, an ideal length for transportation by cargo truck and boat. The diameter is normally 40 mm. A worker may cut a bamboo short or extend the length by joining two bamboos together, according to his needs.

### Bamboo scaffolds and steel scaffolds

A bamboo scaffold and a steel scaffold each has its advantages and disadvantages. The former is more convenient to build and cheaper in price while the latter is stronger and requires less skill to build.

### Single scaffold and double scaffold

As local legislation prohibits workers from working on a single scaffold nowadays, most single scaffolds are made for protective uses only. For example, to demolish certain structures, a single scaffold plus a safety net are set up to prevent smaller pieces of debris from falling onto sidewalk. Two single scaffolds make a double-layered scaffold. Required by law, workers are only allowed to work on a work platform, which is composed of a layer of wooden planks laying at a mid-level of a double-layered scaffold.

### Double scaffold and work platform

The building of a scaffold starts from the corner. A long bamboo is set at an inclination of 45°.  These inclined/tilted bamboos are formed into scaffolds horizontally first, then extended upwards. When the outer layer of a double scaffold is built, a platform is formed by laying wooden planks on a particular level. In the past, workers used to paint walls on a single scaffold. As smoothening work requires more tools, workers now prefer to work on a platform.

### Single scaffold and double scaffold on the slope

In rainy seasons, there are more projects to maintain hill slopes. A single scaffold along a slope is used only for clearing grasses and conducting simple surveys. A double scaffold is needed for soil strengthening work. A slope scaffold is made with these steps: a bamboo is placed perpendicular to another bamboo; the third bamboo is placed at 45° against the vertical one to fix the structure. This bamboo at 45° is called “cheung” which is used to balance the bamboos and to fix the shape of a scaffold. The more “cheung” are used, the more stable the scaffold is.

### Work platform of slope scaffolds

A single scaffold along a slope is used only for detecting problems by eye sight. A double scaffold with a work platform is necessary when actual work is to be conducted. Usually a platform is laid with wooden planks. In this photo, bamboos were used instead because it was more convenient to use bamboos in this situation. The government has published a guideline colloquially called “blue-cover book”, which requires the area of a work platform for building construction and renovation to be 0.4 meters in breadth. There is no stipulation for other types of work platform. Mr Chan recalled that a work platform had to be 4 to 5 metres in breadth for holding a large construction machine.

### The mechanics of trigonometry

Mr Chan explained the mechanics of scaffolding from trigonometry.

### A simple scaffold for Chinese opera performance

A scaffold for Chinese opera is different from other types of scaffold. It is a house-like structure built on a large piece of open area according to a designated design. In the whole of Hong Kong, there are only 2-3 scaffolding companies specializing in this kind of scaffold as orders only come during peak seasons. A scaffold of this type is characterized by a wide front, with two bamboos setting on the left and the right each. One is called tiger door “cheung” and the other called wolf tooth “cheung”.