How to Repair a Cracked Wall Using Helical Wire
Introduction to Crack Stitching
How to Repair a Cracked Wall Using Helical Wire Reinforcement System
Crack stitching can be successfully undertaken using SpiraCoil Crack Stitching Kit or individual products from the SkilledBuild range. SkilledBuild repair systems are of a premium professional quality but may also be successfully used by suitably competent DIYers.
SpiraCoil Crack Repair System uses specially developed cementitious masonry repair grout and stainless steel helical masonry repair bars and is ideally suited to vertical or diagonal cracks in masonry (brick), concrete block, stone walls, Nofines and Easiform concrete panels. Both internal and external cracks can be repaired using the samemethods.
The system is time proven and specified by surveyors, engineers/insurance companies and most conservation officers to provide practical long term repair. Like all the most successful systems, the product is simple to use. Cracks are stabilised and structural integrity reinstated by bonding bars into a cut channel with the aid of a special non-shrink masonry repair grout or optionally a 2-part epoxy resin. Repair channels (slots) can often be visually hidden by cutting along existing mortar joints and later re-pointed to match the surrounding masonry mortar. A near invisible repair is achievable.
SpiraCoil Helical Bars reconnect walls either side of a crack and reinstate structural integrity to the damaged wall. The masonry repair bars extend beyond the cracks, helping to stabilise the structure and provide some resistance against future cracking by diffusing stresses along a greater area of the wall.
SpiraGrout is a high performance, thixotropic cement based crack stitch grout. The masonry repair grout fills the repair channel adhering to the helix of the helical bar and achieves an excellent bond to the channel substrates. The masonry repair grout cures rapidly to hold the helical bar in position and develops considerable compressive strength and resists axial deflection of the rod under load conditions. In short the repair is tough but flexible enough to accept normal building movement and expansion/contraction forces.
Unlike standard masonry repair grouts, SpiraGrout is fully shrinkage compensated preventing contraction over the curing process and maintaining compressive strength and adhesion.
Good preparation is ‘key’ to success. SkilledBuild advocates that this preparation also includes assessment of Health & Safety risks before work starts. Persons should be suitably skilled in the use of power tools and all appropriate Personal Protection Equipment (PPE) be worn. Consider safe access to the work area and the stability of the structure to be worked on.
Cost effective and more stable than other repair systems.
Minimises the likelihood of further cracking, unlike injection methods).
A permanent none destructive repair.
No special skills required for installation.
Removes the need to rebuild walls.
Movement stresses diffused over the complete length of the repair bar.
No additional fixings, plates or screws required.
SpiraCoil is manufactured from durable (304 grade) austenitic stainless steel.
SpiraCoil have a superb combination of axial strength and flexibility.
Masonry remains flexible enough to accommodate natural building movement.
Directions for use:
1. Where the repair will be readily visible. Install into horizontal mortar joints in brick, blockwork and stone Installation can be in chases directly through brickwork, blockwork or stone. However, this will affect the final appearance unless later covered by plaster, render, panelling or paint finish.
NOTE: Do not cut into hollow blocks – for hollow block repairs use mortar joints only.
2. Rake out or cut slots into the horizontal mortar beds to the required depth (see fig 2) It is important to cut the slots to an even depth and as straight as possible with no steps or kinks. Repairs in random block stone walls often creates a problem to achieve long straight cuts in the mortar joints and sometimes requires creating a new joint line across a number of stones.
3. Repair channels/slots are best achieved using twin bladed diamond tipped wall chasing units, which are often available for hire. These chasers are generally considered to be far safer than hand held grinders and more accurate in use. They also possess the added advantage of being able to connect to a builders dust extraction vacuum, particularly important when working inside a property on internal cracks. Suitably skilled persons may be able to grind out the slot using a hand held 9” grinder fitted with a masonry grinding wheel but considerable care is required to ensure that the channel is of a uniform depth or weakness or excessive use of grout may occur.
Fig1 Creating the repair channels with chasing tool
Installation Tools Required
4. At this stage consideration should be given towards the need to repair the crack itself. If left, cracks create both failure in weather proofing quality and a weakness in the wall.Many cracks will follow the mortar lines in masonry and stonework. These are easily repaired by deep-bed re-pointing. At this stage any cracked mortar not already ground out by the repair channels/slots should be raked or ground out to at least 25mm depth
behind the brick face using a bolster chisel, or SkilledBuild Mortar Rake or a small grinder fitted with a mortar disc.
5. Cracks that have travelled through bricks and blocks may require additional attention. You can elect to leave bricks with very fine/tight cracks. An elegant option is to repair the brick/block/stone without the need for removal using a Skilled Build Fine Crack Epoxy Repair Kit. (available online soon). Significant cracks through bricks (like the ones in the image in fig 2) should be repaired. If appearance is not important then this can be wedged with slate and pointed with mortar.
Damaged bricks can be carefully removed and suitable replacements inserted. If the matching of replacement materials is problematic then carefully remove the damaged bricks and bond the broken halves using a suitable epoxy resin. The repaired bricks can then be carefully refitted and fixed in place using cement mortar or preferably a SkilledBuild resin or SpiraGrout. Suitable brick bonding epoxy resins can be identified using the SkilledBuild Resin Selector on the website.
6. The installed masonry repair bars should extend at least 500mm either side of the vertical crack and to the correct depth dependent on the wall thickness. (See fig 2)
7. Normally vertical spacing of the masonry repair bars is every 3-6 brick courses (typically every 4th course) but check with a structural engineer if in doubt. Each channel should be cut slightly longer than the bar length to be installed to enable a full depth cut of the grinder disk to extend the full length of the helical masonry repair bar. This typically requires extending the grinder cut 75mm beyond the length of each helical repair bar. Experienced installers often mark up the channels to be cut using a chalk stick, thereby eliminating the possibility of cutting incorrect lengths or positions.
The more helical bars inserted the stronger the repair. NOTE: When repairing cracks in rendered or plastered walls inside properties the depth of the repair channel/slot is always measured from the brickface and does not include the thickness of render/plaster.
E.g. A wall with 20mm of plaster which requires a 35mm depth of slot, will need the slot cutting 55mm into the plastered finish to achieve the correct depth. In some instances it may be more practical to remove plaster from around the local area being repaired.
8. Ensure the repair channel is left clean and all old mortar is fully removed from the top and bottom faces using a scraper or bolster chisel, as necessary. The surfaces of the bricks should be clearly visible within the slot. This is essential to ensure the grout bonds fully.
9. Flush the channel thoroughly with water from a sprayer or hose to remove final traces of dust and to reduce the moisture suction of the brickwork on the grout. Ensure that the bricks are fully wetted but no standing water should be present when masonry repair grout is injected.
10. Now prepare the SpiraCoil Helical Bar. If necessary cut bars to the required length. 5 metre & 10 metre bars are supplied as coils and may require gentle bending tostraighten curves, ensuring that it will lay in the correct position in the channel without the need for wedging. Test the bar in the prepared slot. It is best to use continuous bars for the full length of each repair, but if your bars are not long enough allow a minimum of 250mm overlap of each bar.
If using 1 metre bars or 1.5 metre bars use the full length. If the crack is within 500mm of a corner then extend the channel around the corner and bend the bar at 90 degrees to follow the rule of a minimum of 500 mm past the crack.
Cutting the Helical Wire to length Mixing the non shrink grout Adding the grout to the gun
NOTE: Preparation to this stage is important as once mixed the grout has limited time of workability particularly in warm conditions.
11. Mix the SpiraGrout thoroughly (see correct product user guide for more information) using a paddle mixer and load into a pointing gun.
12. Then inject a bead of masonry repair grout to the back of the slot across the full length to approximately 10mm to 15mm depth.
13. Take the prepared masonry repair bar and insert into the repair channel – use a finger trowel to gently press bar into the face of the Grout.
Applying the non shrink grout Installing the helical bar Finger trowel the repair channel
14. Inject a second bead of grout over the bar and across the full length to approximately10mm to 15mm depth – now run a finger trowel along the grout to press firmly into the masonry repair slot.
15. If required, repoint the masonry repair channel and any ground out cracks with asuitable colour matched mortar. Repointing may be undertaken as soon as the grout has hardened. If the wall is to be re-rendered or plastered there is no necessity torepoint first.
16. Failure to follow this procedure will result in reduced effectiveness of the repair.
Note: It is good practice to photograph the repair channels in walls prior to re-pointing or plastering to enable the exact position of the repairs to be identified in the future. This will result in future building works of re-pointing bars being less likely to damage the crack-stitching bars. If the outside of the property is to be generally re-pointed after crack-stitching bars are inserted the positions of the bars should be identified and marked and under no circumstances should masonry repair grout be ground out or damage to the helical bar repair will result.
SkilledBuild is committed to development and supply of quality products and may substitute or change product branding or specification or technical data without notice. Always check for latest information.
All information provided is based on practical tests & published data and is intended to guide a competent DIY user or contractor in the typical use of products for minor works but is without guarantee. If a failure of the works will be costly to repair or hazardous then design & execution must be undertaken by competent persons. Further advice should be sort from a suitably qualified advisor. Skilled Build may be able to answer simple product enquiries.
Since application and working and user competence is beyond our control, no liability of the supplier can be derived from the contents of information sheets or other general information provided. Any statements made beyond the contents of SkilledBuild’s website or product labels must be confirmed in writing by the supplier.