Shoring is the construction of a temporary support structure designed to stabilize an unsafe or weakened structure during repair or alteration work. It is primarily used to provide lateral support to walls or vertical support to floors and roofs when their stability is compromised. Shoring is commonly employed in situations such as bulging walls, cracks caused by unequal settlement of foundations, demolition of adjacent buildings, or when new openings are to be created or enlarged in existing walls.

Types of Shoring

Shoring can be broadly categorized into three types:

1. Raking Shoring
2. Flying Shoring
3. Dead Shoring

Each type has a specific purpose and structural arrangement depending on the requirements of the project.

Raking Shoring

Raking shoring uses inclined members called rakers to provide lateral support to walls. This method is often adopted when a wall is bulging outwards and requires temporary reinforcement.

Components of Raking Shoring

• Rakers (Inclined Members): The primary supports inclined against the wall.
• Wall Plate: Placed between the wall and the raker to distribute the load.
• Needles: Horizontal beams that support the wall and transfer load to the rakers.
• Cleats: Fasteners securing various members together.
• Bracing: Provides stability to the rakers by preventing sideways movement.
• Sole Plate: Base support embedded in the ground for the rakers.

Key Considerations

• Rakers are usually inclined at an angle of 45° to 75°, with 45° being ideal for stability.
• For taller buildings, a secondary “rider raker” may be used to reduce the length of the main raker.
• Proper bracing is essential at regular intervals to ensure stability.
• The size of the rakers must be selected based on the anticipated lateral thrust from the wall.
• The centerline of the raker should intersect the wall’s centerline at the floor level for optimal load transfer.
• Shoring should be spaced approximately 3 to 4.5 meters apart to cover longer stretches of wall.
• Sole plates must be firmly embedded and appropriately sized to distribute the load.
• Wedges should be avoided on sole plates to prevent slippage caused by vibrations.

This method is effective in stabilizing walls temporarily while repairs or alterations are carried out.

Flying Shoring

Flying shoring is used primarily when two adjacent buildings share a party wall and the building in between is being demolished or rebuilt. In this case, the party walls of the adjoining buildings require temporary support without direct ground contact.

Characteristics of Flying Shoring

• The shores do not rest on the ground but are instead supported by a system of horizontal and inclined struts.
• Wall Plates: Fixed against the walls to distribute the load.
• Needles and Cleats: These transfer load between the struts and wall plates.
• Horizontal Struts (Horizontal Shores): Span the gap between two walls to provide lateral support.
• Inclined Struts: Provide additional stability by resisting lateral forces.
• Straining Pieces (Straining Sills): Connected at the feet of inclined struts to hold them in place.

When the distance between walls is large, a simple horizontal shore may not be sufficient, and a trussed framework of members may be required for adequate support.

Flying shores are crucial in ensuring the safety of structures during demolition and reconstruction projects without compromising the integrity of the neighboring buildings.

Dead Shoring

Dead shoring provides vertical support to walls, roofs, and floors when the lower portion of a wall has been removed or is being rebuilt. This method transfers the load of the upper structure safely to the ground.

Components of Dead Shoring

• Needles: Horizontal beams inserted into holes cut in the wall to carry the weight of the structure above.
• Dead Shores: Vertical props placed under the needles to transfer the load to the foundation below.

Procedure for Installing Dead Shores

• Holes are cut into the wall at a height that allows the insertion of needles, spaced between 1.2 to 1.8 meters apart, depending on the masonry type.
• The needles, made of timber or steel, are inserted into these holes and extend beyond the wall on either side.
• Vertical dead shores are then placed beneath the ends of the needles to support the load.
• Props are positioned away from the wall to provide workspace and are tightened using folding wedges to ensure stability.
• The junction between the needle and prop is secured using dogs (metal fasteners).
• Doors, windows, and other openings are well-strutted before dismantling work begins to prevent structural failure.
• Floors and roofs are independently supported to relieve load from the walls during the process.
• Due to the risk of vibrations and shocks when cutting walls, additional raking shores may be installed as a safety precaution.

Dead shoring is essential when creating new openings or rebuilding load-bearing walls to maintain the structural integrity of the building during construction activities.

Conclusion

Shoring is a vital construction technique used to stabilize and support structures temporarily during repairs, demolition, or modifications. Understanding the different types—raking, flying, and dead shoring—and their appropriate applications ensures that buildings remain safe and secure throughout construction activities. Proper design, careful installation, and adherence to safety measures are crucial for effective shoring and the successful completion of structural work.