Introduction

The advantages of using Masonry Reinforcement have been known to engineers for many years, but it was not until the early 1990s that corrosion resistant stainless steels were used on a large scale to repair and strengthen damaged masonry structures.

Masonry has excellent compessive qualities and the majority of buildings constructed using this material last for many years with little maintenance. However, masonry has no significant tensile strength and differential movement caused by substrata changes, moisture or thermal effects usually causes cracking followed by general deterioration of the structure.

The Principle

Prior to the introduction of masonry reinforcement partial underpinning was often used, but this can result in further damage caused by differential movement between the original foundation and the underpinned section.

The introduction of stainless steel to reinforce a masonry panel provides it with the ability to resist tensile forces however generated. The Bersche-Rolt system of reinforcement is widely used throughout the UK and it is based on the principle of reinforcing the walls from the outside to form composite masonry beams, which spread the imposed loads evenly throughout the structure, which then behaves as a single unit. Masonry reinforcement costs less than underpinning, it is less disruptive and shows considerable cost savings when compared with pile and raft schemes.

The Design

The design is prepared after the cause of the defects has been established, and any remedial works to drains, trees, etc. has been carried out. A peiod of monitoring is often neccessary in order to establish the cause of the differntial movement and resultant damage.

High tensile stainless steel reinforcing bars are bonded centrally into holes or grooves cut horizontally or vertically in the walls. The reinforcing bars vary in diameter and length but all have a solid cross section with a ribbed surface and spacers in order to give superior bond and tensile performance.

The design may allow for forming masonry beams for the full perimeter of the building or alternatively for local stiffening and restraint of damaged areas.

Advantages of Masonry Reinforcement

Reinforcement may be installed quickly from outside the building, with little tenant disruption
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Masonry reinforcement is usually cheaper than underpinning.
Partial underpinning creates hard spots which often causes problems, while masonry reinforcement does not interfere with the normal movement of the building in response to climatic changes which affect the substrata.
Fixed price contracts, insured guarantees.
The cost of Underpinning depends on the condition of the substrata and often goes over budget, there should be no hidde