Concrete crack repairs Melbourne

Not every crack means the same thing, and the repair method depends entirely on which of these you are dealing with:

• Shrinkage cracking Fine, shallow, often map-like cracks that appear as concrete cures. Usually cosmetic, but they let water in.
• Settlement and ground movement Melbourne’s reactive clay soils swell and shrink through wet and dry seasons, which moves slabs and footings. These cracks typically widen over time and are often diagonal.
• Concrete cancer (spalling) Water reaches the steel reinforcement, the steel rusts, and rust expands. That expansion pushes the concrete off from the inside, so you see cracking, bubbling, then chunks falling away with rusted bar exposed underneath.
• Overloading or inadequate reinforcement Cracks that track along the line of the reinforcing steel or appear at points of stress.
• Thermal movement Expansion and contraction where no control joint was provided.

Concrete cancer is the one worth acting on early. Once reinforcement starts corroding, the process accelerates: the expanding rust opens more cracks, more cracks let in more water, and more water corrodes more steel. On balconies, carparks and older apartment blocks it can move from a hairline crack to a structural repair bill in a few seasons.

Signs to look for are rust staining on the concrete face, hollow or drummy sounding areas when tapped, bubbling or lifting paint, and pieces of concrete flaking off with rusted steel visible behind them.

We match the method to the diagnosis rather than applying one product to everything:

• Epoxy resin injection For structural cracks where the two faces need to be bonded back into a single element.
• Polyurethane injection Where the priority is stopping active water movement through the crack.
• Concrete cancer remediation Cutting back to sound concrete, exposing and cleaning the corroded reinforcement, treating it with an anti-corrosion primer, and reinstating with a polymer-modified repair mortar.
• HeliFix crack stitching Where cracking runs through masonry as well as concrete and the crack needs to be tied back together across its full length.
• Waterproofing and protective coatings So the repair is not undone by the same water that caused the problem.
• Joint installation Where movement needs somewhere to go rather than being resisted.

We look at the crack pattern, width and direction, check for drumminess and cover to the reinforcement, trace where water is entering, and look at the surrounding drainage and ground conditions. You get a written explanation of what is actually happening and a repair option costed against it — including, where it is honestly the case, being told that a crack is cosmetic and does not need structural work.

Book an inspection if you can see rust stains, if a crack is wider than about 2mm or has visibly grown, if there is drumminess or flaking, if water is coming through into the space below, or if cracking has appeared after nearby excavation or a change in drainage.

Concrete cancer remediation is the concrete repair we do most, and it has to be done fully or it comes back. The steps are the same whether it is a balcony edge, a carpark soffit or a slab edge on a house:

1. Map the extent — tapping the concrete to find every drummy area, not just the piece that has fallen off. The corroded steel always extends further than the visible damage.
2. Break out to sound concrete — removing all delaminated concrete and cutting back around the reinforcement so it can be cleaned on every side.
3. Clean and treat the steel — abrasive cleaning to bright metal, then an anti-corrosion primer. Where steel has lost significant section, additional bars are fixed alongside.
4. Reinstate — a polymer-modified, low-shrink repair mortar applied in layers and finished to match the original profile.
5. Protect — an anti-carbonation or waterproof coating over the repair and the surrounding concrete, so the same water cannot start the process again.

Skipping the last two steps is the most common reason a concrete cancer repair fails within a few years. Patching mortar over rusty steel simply hides the problem while it keeps growing.

• Balcony slabs and edges The most common site. Water through tiled balconies reaches the slab reinforcement. Often repaired together with balcony waterproofing.
• Carpark soffits and columns Basement and undercroft carparks in apartment buildings, where spalling concrete overhead is a safety issue as well as a structural one.
• Slab edges and footings Exposed slab edges on houses and units, and footings where the cover to the steel was inadequate from the start.
• Retaining and boundary walls Cracked and leaning concrete and concrete block walls, usually from water build-up behind them and ground movement.
• Concrete stairs, landings and walkways External common-property stairs and walkways on older blocks, where salts and weather have got to the steel.
• Rendered concrete facades Cracking through the render that originates in the concrete behind it, which needs the concrete repaired before the render repair will hold.

Not every crack in concrete needs structural repair, and it helps to know what you are looking at before you call anyone. Fine random cracking across a slab surface is usually shrinkage from curing and is cosmetic, though it should be sealed to keep water out. Straight cracks at regular spacing on a large slab are often just where control joints should have been cut. Cracks that are wider than about 2mm, that are wider at one end than the other, that have one side higher than the other, that run diagonally from corners of openings, or that are growing, point to movement or reinforcement corrosion and need a proper assessment.

Where cracking runs through both concrete and masonry, or a crack needs to be tied across its full length rather than just sealed, we use HeliFix crack stitching. We are one of only three certified HeliFix brick and concrete specialists in Melbourne, so the assessment and the stitching are done by the same people.

Concrete repair is priced on the area and depth of breakout, how much reinforcement has to be treated or supplemented, the access (a balcony soffit two floors up needs a scaffold or elevated work platform), whether waterproofing or a protective coating goes over the repair, and whether the concrete has to carry load during the work and needs temporary propping. Small slab-edge repairs on a house are at the low end; a staged carpark remediation programme is at the other.

The inspection and quote are free, and where a crack is cosmetic we say so. We would rather tell you a crack needs sealing than sell you a structural repair it does not need.

We work regularly with owners corporations, building managers and property managers on concrete remediation in apartment blocks, carparks and commercial buildings. That includes staged programmes where a whole elevation of balconies or a carpark is done in sections so residents keep access, and written condition assessments with photographs suitable for committee approval, engineer review and insurance. Where a structural engineer’s input is needed, we work with your engineer or can recommend one we have worked with.

• What is concrete cancer? Concrete cancer, or spalling, is what happens when water reaches the steel reinforcement inside concrete. The steel rusts, rust takes up more space than steel, and the expansion cracks the concrete and pushes it off from the inside. It gets worse on its own and should be repaired early.
• Can concrete cancer be repaired or does the concrete need replacing? In most cases it can be repaired. Damaged concrete is broken out to sound material, the steel is cleaned and treated, the concrete is reinstated with a repair mortar and the area is coated to keep water out. Replacement is only needed where the element has lost too much section to be repaired safely, which an assessment will show.
• How do you know how far the damage goes? By tapping the concrete: corroded areas sound hollow or drummy before they fall off. We map the full drummy area before breaking out, because the rusting steel always extends beyond the piece that has visibly failed.
• Is a crack in my concrete slab structural? Fine random surface cracking is usually shrinkage and cosmetic. Cracks over about 2mm, cracks that are growing, cracks with one side higher than the other, or cracks with rust staining need to be assessed. We tell you which type you have and only recommend structural repair where it is needed.
• How long does concrete cancer repair take? A small slab edge or a single balcony soffit is usually a few days including curing of the repair mortar and coating. Larger programmes on apartment buildings are staged over weeks so residents keep access.
• Will the repair be visible? The repair mortar is finished to match the original profile and the area is usually coated, so on a painted or coated surface it is not visible. On bare off-form concrete a repair can be seen up close, and we will tell you that before starting.
• Do you repair concrete in carparks and apartment buildings? Yes. Carpark soffits, columns, balcony slabs, stairs and walkways on apartment and commercial buildings are a large part of our concrete work, and we provide the written assessments owners corporations need.

Concrete cracking often appears alongside other problems. We also carry out render crack repairs, leaking balcony repairs and restoration, and cladding repairs and restoration.

• HeliFix crack stitching
• Leaking balcony repairs
• Render crack repairs
• Cladding repairs