Pinning masonry arches

Pinning masonry arches with helical reinforcement rods is a highly effective way of repairing and strengthening old brick or stone arched structures. Installation of the heavy-duty helical ties maintains arching-action, restrains thrust and prevents failing arches from collapsing.

A masonry arch transfers vertical loadings via its base to abutments that restrain the resulting thrust, help maintain arching action and prevent the arch from collapsing. Old arches may fail due to tension developing in the arch, causing separation of arch layers or movement of the keystones.   Early signs of failure become apparent when an arch sags or cracks. This cracking and displacement failure is potentially dangerous and may lead to instability.

The introduction of external bracing can provide additional resistance. If tension develops in the masonry, adding reinforcing ties increase resistance to tension forces and reconnect separated arch-layers or keystones. Pinning masonry arches to the brickwork or stonework above can increase the arch’s effective depth and load capacity.

Thor Helical have two systems for reinforcing failed masonry arches.

Chemical Fix Grout Tie for strengthening brick & stone arches

Helical bars, fully grouted into deep bores drilled into the masonry, can restore the strength of brick arches. Holes are typically 14-18mm in diameter. The process involves injecting a cement-based grout into the holes and inserting a helical tie bar into the unset grout. The continuous deep trough of the helix provides an excellent key for locking the tie bar in place once the grout cures and sets.

Mechanical Fix Strap Tie for pinning masonry arches

Where material compatibility, temperature extremes, speed and cleanliness is an issue, one should consider reinforcing masonry arches with a heavy-duty self-tapping helical tie rod driven deep into the masonry. A small pilot hole, typically 8mm in diameter, is drilled into the masonry, and a 12mm heavy duty tie rod is hammer-driven into the pilot hole. The helical strapping ties corkscrew into brick and stone, cutting twin-start self-tapping threads to provide a high strength mechanical connection.

What makes the Thor Helical 12mm tie a cut above the rest?

  • Ties require no bonding agents.
  • Suitable for use in situations where cement grouts cause material compatibility issues
  • Suitable for use in freezing temperatures
  • Suitable for pinning masonry arches at high speed, typical installation rates are 10 times faster than chemical fix tie bars.
  • Small entry hole for minimal disfigurement of masonry
  • Patented precise pitch engineering delivers product consistency with unrivalled performance.
  • Patented pinning system with unique tie-driving shank
  • Safe, reliable, easy-to-use, and low-cost SDS setting tool (patented).
  • Ties conform to conditions for CE marking according to BS EN 845-1 2013, meeting the performance requirements for a tensile load capacity of at least 8kN.