Colne Valley Preservations Ltd
Remedial Treatment Specialists
Wall Tie Replacements
Wall ties are an essential element for the stability of a cavity wall structure, tying its weather protecting brick facade to the main body of a building.An effective brick tie system transfers static and live loads across the cavity, enabling load sharing by both inner and outer walls. Typically cavity wall ties are bedded in a mortar bed joint as a building is constructed.
Cavity wall tie failure can be a consequnce of a construction defect; for example where the original 'built in' cavity wall ties have been omitted, incorrectly fixed or fitted with brick tiesthat are to short. Alternatively failure may be a result of a buildings aging process, whereby wall tie corrosion may have compromised the walls load sharing capabilities.
Over time motar joints, which host the wall ties, undergo a chemical change through carbonation. The Motar becomes aggressive to the steel base and its protective coatings, reducing the life expectancy of the cavity tie systems to a little as 26 years. the design life of the building is typically much longer than this period and it therefore follows that at some point a remedial retrofit replacement of the brick ties may be necessary if the stability and load sharing capacity of the wall is to be maintained.
As wall tie corrosion sets in, the mild steel brick ties generate a build up of iron oxide layers which occupy a greater volume than that of non-corroded steel. In most cases, particularly when wire wall ties have been used, the increase in the volume is accommodated in the motar bed as the cavity ties corrode. In such cases there may be little sign that the outer facade is free standing and the walls not supported, some of the wall may appear bulged.
In other case, particularly when sheet steel or vertical twist ties have been used in less forgiving motars, the iron oxide build up may have the effect of lifting the masonry above a line of insitu brick ties . If expansion is widespread and present along several rows of corroding cavity wall ties , a tel-tale patters of horizontal cracks may be produced along each wall tie course.
Lateral Restraints
Lateral restraints are wall ties used for restraining bulging walls.
Lateral restraints are fitted from outside the property with the minimum of disturbance - in most cases just lift a few floor boards to determine the position of the joist and to ensure wires or pipes that may be hiden are avoided during tie installation.
Each of our lateral restraints wall ties have a drill like leading end for cutting into softwood. Using a drill, simply wind the lateral restraint ties into the timbers and resin fix the masonry end.
Crack Repair
Crack Stitching bars are heavy duty helical bars (8kN+) and are ideal for the masonry repair of wall cracks where shear strength is an issue. This 6mm diameter wall crack stitching reinforcement offers extra performance to other helical bar type products by significantly increasing the shear, tensile and flexural strength of cracked masonry walls.
The hi - fin design on our crack stitching also makes the Thor Helical Remedial Crack Stitching products ideal for grouting into motar beds to retrospectively reinforce distressed masonry and to control cracking by distributing forces back into the structure. The various Thor Helical Remedial sections are directly proportionate to one another, providing opportunity for cross correlation of performance characteristics to be used in specification design.
