This crack stitching guide page is intended as an overview on crack stitching for beginners but assumes a working knowledge of construction techniques, materials and Health and Safety. We explain how to do crack stitching in straightforward terms.
This ‘how to’ crack stitch guide applies to carrying out basic crack stitching – if you’re not sure whether this is the appropriate method for your particular situation, please contact us for help or advice.
Anyone undertaking construction work should produce method statements and carry out risk assessments to ensure any measures are identified to protect the health and safety of operatives and third parties.
Tools and Materials
To carry out basic crack stitching you’ll need the following tools and materials. Where links are provided, you can buy items directly from our online shop.
- Cement-Based (cementitious) Grout (an alternative to this is resin but we’d always recommend using grout)
- Stainless Steel Helical Bar
- Slot Cutting Tool (with suitable extraction) – for cutting out slots in the masonry
- Vacuum – for clearing out debris from the slots
- Water spray bottle – for washing out slots
- Mixing paddle – for mixing the grout
- Grout gun – for pumping the grout into the slot
- Nozzle for grout gun – to enable grout to be pumped to the back of the slot
- Finger Trowel – for ironing in the grout and helical bar
Depending on the particular job, you may also need the following:
- Bolt cutters – for cutting the helical bar
The method for crack stitching is as follows:
- 1. Rake out or cut slots into horizontal mortar joint to specified depth and at required vertical spacing.
- 2. Vacuum out the slots and thoroughly flush with water.
- 3. Cut the helical bar to length and have it close to hand.
- 4. Mix the grout in the bucket as per the instructions (all of our tubs of grout come with an instruction leaflet or click here for a picture guide).
- 5. Load the grout into a grout gun and pump a bead of grout into the back of the slot.
- 6. Push the helical bar into the grout to obtain good coverage – use a finger trowel if necessary.
- 7. Pump a bead of grout over the exposed bar and iron into the slot using a finger trowel.
- 8. Re-Point or fill the slot and leave ready for decoration.
Guidance notes are as follows:
- Depth of slot to be 25 to 35 mm.
- Helical bar to extend a minimum of 500 mm each side of the crack. We sell 1m lengths of bar for single cracks and 10m lengths which can be continued across as wall where multiple cracks are present.
- Normal vertical spacing of crack stitches is 450 mm (6 brick courses).
- Where a crack is within 500 mm of the end of a wall (as in A above) the helical bar is to be continued for at least 100 mm around the corner and fixed into the adjoining wall.
- Where a crack is within 500 mm of an opening (as in B above) the helical bar is to be bent back and fixed into the reveal.
- Where can I read more? – We have a range of Standard Details which cover different types of masonry repair but if you need any further guidance please feel to contact us by email or phone.
- How much grout will I need? – As a general rule of thumb we allow a 3 litre tub of grout per 10 linear metres of slot (or a 6 litre tub for 20 metres). This assumes a 10mm width slot filled to 25mm depth so assumes final re-pointing with normal sand/cement mortar.
- What about using resin instead of grout? – Some installers prefer to use resin rather than grout but we would always recommend grout. If you’re doing very small quantities or an engineer has specified resin for a specific reason then you may wish to use resin which we also sell in our online shop.
- How do I cut the slots? – For small quantities of crack stitching you can use a mortar raking chisel in an SDS hammer drill or a rotary mortar rake in an angle grinder. For any larger quantity, we would recommend the use of a wall chaser such as the ‘Hilti DC-SE 20’ or double-bladed grinder such as the ‘Sparky FK652’. With any method you should make sure you have suitable dust extraction and carry out an assessment of the risks and implement measures to reduce risks where possible.