Temporary construction, types and requirements

Temporary construction is any support, framework or structure that is put up for a limited period to help the construction, repair or alteration of a permanent building, and is removed when its purpose is served.

Types

1. Scaffolding

Scaffolding is a temporary framework of timber, bamboo or steel erected beside a building so that workers and materials can be placed at height while the structure is built, repaired or cleaned.

• Single (brick layer's) scaffold: one row of standards joined by ledgers, with putlogs resting on the wall.
• Double (mason's) scaffold: two rows of standards, used for stone masonry where holes in the wall are not allowed.
• Cantilever scaffold: needles projecting from the wall support the platform where ground support is not possible.

  single           double          cantilever
  wall|--ledger    wall| |--|      wall|=needle=>
      |putlog          |putlog          |  platform
      |standard      2 standards      struts /

2. Formwork: moulds of timber, plywood or steel that give shape to concrete.

3. Shoring: raking, flying and dead shores that support unsafe walls.

        wall plate
   wall |\ raker
   wall | \
   wall |  \
   _____|___\__ sole plate

4. Underpinning: strengthening a foundation by deeper or wider construction.

5. Timbering of trenches: poling boards, struts and walings that hold the trench sides.

Requirements of temporary construction

• Strength and stability: must carry all dead, live and impact loads, with a factor of safety (generally 4).
• Rigidity: minimal deflection and no sway.
• Safe and sound materials: good timber without defects, steel free from rust.
• Easy erection and dismantling: quick work and re-use.
• Economy: low cost, light weight and possible re-use.
• Safety: guard rails, toe boards, ladders, access and inspection.
• Correct alignment and tight joints (formwork must be leakproof).
• Foundation: firm, level sole plates.