Not all cracks in buildings are structural. Fine hairline cracks in plaster are cosmetic. Wide diagonal cracks running through brickwork are structural. Knowing the difference between cracks that need urgent repair and cracks that can be monitored prevents both unnecessary expense and dangerous delays.
Structural crack repairs fix cracks that show that the structure is still moving or is weak and needs work.
Identifying Structural Versus Non-Structural Cracks
Structural cracks usually go through several layers of brickwork or concrete, are wider than 5mm, and are diagonal instead of vertical. They often show up near the corners of buildings, around windows and doors, or where different parts of the building meet.
Non-structural cracks are usually fine hairlines in plaster, vertical cracks at wall junctions, or settlement cracks that have stabilised. These can be filled and decorated over without structural repair.
The key question is whether the crack is active, continuing to widen, or dormant, stable and unchanged for months or years. Active cracks require structural repair. Dormant cracks may only need cosmetic treatment.
Monitoring Crack Movement
Before expensive structural repairs, monitoring establishes whether cracks are active. Glass tell-tales or graduated crack monitors are fixed across cracks. If the crack widens, the tell-tale breaks or the monitor shows increased gap width.
Monitoring periods typically run 6-12 months to capture seasonal movement. Some cracks widen in summer drought when clay soils shrink, then close partially in winter. This seasonal pattern indicates ongoing foundation movement requiring stabilisation.
Crack Stitching and Reinforcement
Structural crack repair often involves crack stitching using helical stainless steel bars bonded into slots cut in the mortar beds on either side of the crack. This provides tensile strength across the crack, preventing further opening whilst allowing the wall to function as a structural element.
The bars are bonded with high-strength resin or cementitious grout. Once set, the wall regains integrity. Surface cracks are filled and can be rendered or pointed to restore appearance.
Concrete Crack Injection
Using resin or polyurethane injection to fix cracks in concrete structures is common. The crack is cleaned and sealed at the top, and then injection ports are put in at regular intervals along the crack. Under pressure, low-viscosity resin is pumped into the crack, filling it completely from the bottom to the top.
This puts the separated concrete back together, makes it waterproof again, and stops it from getting worse. You can find it in concrete foundations, basement walls, and structural slabs.
When fixing cracks isn’t enough
Some cracks show that the damage is so bad that just fixing it isn’t enough. You may need to strengthen or rebuild the structure underneath. Structural engineers decide if fixing the cracks will make the structure strong enough again or if more work needs to be done.
Trying to fix cracks when the cause of the movement hasn’t been found just puts off the failure that will happen anyway. Before fixing cracks in walls caused by foundation subsidence, the foundation needs to be underpinned.
Stopping More Cracks
Fixing structural cracks is only half the battle; you also need to deal with the cause to stop it from happening again. This could mean fixing leaking services that are weakening the foundations, managing tree roots near the building, or improving drainage so that water doesn’t pool near the foundations.
Cracks that have been fixed often reopen because the underlying problem hasn’t been fixed.
Insurance Coverage
Structural crack repairs caused by insured risks like subsidence are usually covered, but there may be a policy excess. Most of the time, gradual deterioration from bad maintenance or age-related decay is not covered.
Insurance companies need proof from structural engineers that the cracks are new damage to the building and not something that was already there or just cosmetic.
What to Expect for Cost
Structural crack stitching for a single crack could cost between £1,000 and £3,000, depending on how long the crack is and how hard it is to get to. A wall with a lot of cracks could cost anywhere from £5,000 to £10,000. Concrete injection repair costs a lot of money, depending on how deep and wide the crack is. Most of the time, it costs between £500 and £1,000 per crack.
These costs are in addition to fixing the problems that caused the damage in the first place, like foundation problems, which make the repairs much more expensive.
In the UK, professional structural crack repair services can look at, keep an eye on, and fix buildings that have structural cracks.
