Necessity and types of shoring

Shoring is the temporary support given to an unsafe wall, building or structure to prevent it from collapsing, using inclined, horizontal or vertical timber or steel members, until permanent repair or reconstruction is done.

Necessity (conditions for shoring)

• A wall is bulging, leaning or cracked and may collapse.
• An adjacent building is being demolished, or an excavation is made nearby.
• The foundation of the building is weakened (settlement, flood, underpinning work).
• Alterations: removing a wall, opening or pier that carries load from above.
• Damage from an earthquake, fire or vehicle impact.

Types of shoring

1. Raking shore:

Raking (inclined) shore: inclined members (rakers) support a wall from the outside. Rakers are at 60-70 degrees to the ground. At the top they bear on needles fixed through a wall plate that is secured to the wall, and at the bottom they rest on a sole plate on a firm base. Cleats and braces hold the members together.

        wall plate
   wall |==|\ needle
   |    |  | \ raker
   |    |  |  \ cleat
   |    |  |   \
   |    |  |    \
 --+----+--+-----\--- ground
                sole plate

Parts: wall plate, needles, rakers, cleats, braces, sole plate and wedges. Types: simple (single raker), compound/double (two or more rakers meeting the wall at different levels), and multiple raking shores for high walls (up to three storeys).

2. Flying shore:

Flying (horizontal) shore: used when two parallel walls with a narrow gap (3-9 m) between them are to be supported, e.g. when the building between them is demolished. A horizontal shore is fixed between wall plates on the two walls, supported on needles, with inclined struts from lower needles up to straining pieces on the horizontal shore. No part touches the ground, hence "flying".

  wall                                      wall
  |  ||==N====== horizontal shore ======N==||  |
  |  ||     [sp]                  [sp]     ||  |
  |  ||      /                      \      ||  |
  |  ||    /   strut          strut   \    ||  |
  |  ||  /                              \  ||  |
  |  ||N/                                \N||  |
  |  ||                                    ||  |
  || = wall plate, N = needle, [sp] = straining piece

A single flying shore is used for gaps up to about 9 m; a double (compound) flying shore is used for wider gaps. The system is cheaper than raking shores and keeps the ground clear for work.

3. Dead shore:

Dead (vertical) shore: used to support the floors and roofs above when a wall is removed, an opening is made in a lower storey, or the lower wall is repaired. It transfers the vertical load to the ground.

It consists of vertical posts (dead shores) on a sole plate at the bottom, a needle (horizontal beam) passing through the wall at the top, and braces, cleats and wedges to take up the weight.

        floor above
   ____|==needle==|____
   wall| |      | |wall
   wall| | post | |
   wall| | post | |
       |_|______|_|
       sole plate