Helical bars are stainless steel bed joint reinforcement rods used for strengthening and stabilising masonry walls. They can be used during construction but are most often used in remedial applications.
Thor Helical bars are bonded into slots cut into the wall to strap or stitch cracked brickwork. They can be used to create deep masonry beams that reinforce panels of masonry and transfer structural loads from weakened zones to areas having firm support. The bars are ideal for the structural repair and strengthening of sagging or cracked brickwork, such as may be typically caused by:
Lintel Deflection or Arch Failure
It is common to find a flat or shallow arch used for carrying brickwork above an opening. The original timber frame often acts as a fortuitous lintel that adds support the arch. Such arches are sensitive to cracking due to small movements of buttressing masonry. Additionally replacement of the window frame with a uPVC unit can undermine the support and provoke masonry arch failure.
Foundation Movement
It is not uncommon for a foundation pile to slip or a portion of a strip foundation to fail. This removes support part-way along the length of the wall with the result that a vertical crack is generated in the masonry wall over the subsided foundation.
Thermal or Moisture Variations
Cracks can appear when the differing moisture or thermal movements result in tensile stresses that exceed the tensile strength of the materials used to build the wall.
Thor Helical bars are manufactured from round stainless steel wire, which is passed through a series of profiled rolls to progressively alter its shape in cross-section. The shaped wire is then forced through a twisting die to deliver a patented precision-engineered helical reinforcement bar with unique torsional elastic yield characteristics and a tensile strength that is double that of standard stainless steel.
Retrofit bed joint reinforcement may be used for:
- Strapping fractured masonry, a series of helical bars can stitch the cracks to reinstate the structural integrity of the wall.
- Forming deep masonry beams to span openings, or areas of local subsidence, the bars are used in pairs, each pair forming the top or bottom chord of the beam.
The helical bars have a deep and continuous helix that provides an excellent key for chemical bonding agents. When used with WHO-60 polymer modified grout the bed joint reinforcement redistributes loads and enhances the tensile, shear and flexural capacity of the masonry panel. CE Mark testing and the BRE report on masonry beams formed with retrofitted Thor Helical bars bear testament to the effectiveness of this versatile masonry reinforcement system.
