BRE - Retro-installation of bed joint reinforcement in masonry
|Publication Date:||11 October 2004|
Bed joint reinforcement, added during construction, is an accepted technique for making masonry (brick, block and stonework walls tougher, stronger in flexure and tension, and less likely to crack. It is also used with the masonry to generate lintels (beams) within walls. In its traditional form of either 'hoop iron' or mild steel with only limited corrosion protection (galvanising or bitumen) it has a finite life and is expensive to treat or remove. However, austenitic stainless steel (ASS) versions are very durable and are now used widely, particularly for crack control.
For about a decade, the industry has been developing methods for installing bed joint reinforcement into existing walls, ie 'retro reinforcement'. This allows the product to be used for crack repair (stitching), repairing sagging lintels and flat arches, developing arches or cantilevers within a wall to span over patches of subsidence, increasing the flexural strength (out of plane) and shear resistance of walls to combat wind and seismic loading, and reconnecting cracked or parted buttresses. Repair techniques for brickwork and blockwork are explained.
This guide includes tables that list the cross-sectional area and tensile strength of some typical bars, and the published properties of different types of grout. Performance figures for steel and epoxy glass fibre reinforcements are given. Where subsidence of foundations causes cracking of masonry, remedial reinforcement, combined in most cases with new piles, can provide a cheaper and less invasive solution than massive strip underpinning works. Illustrations show typical problems and solutions. 8 pages.