Home Renovation

Tiling Over Cracked Concrete

An interesting question was posed today and I think we have an answer….

When tiling over an existing, cracked concrete slab you run the risk of cracks appearing in the tiles above the crack in the concrete.

Repair Options

We’d normally isolate the tiles from the existing cracked concrete with an unbonded (full strength) overlay or topping slab. An even better, although more expensive, option is to demolish the slab and pour a new structural slab.

Butterfly Stitches

However if there aren’t many cracks in the concrete slab and head height is limited, then you might be able to hold the cracks closed with butterfly stitches.

Butterfly strips on chin
Image courtesy of

Not these kind, but the idea is the same. Steel reinforcement cut into the slab to tie and hold the crack closed.

Repair Cracked Brickwork

The same idea is being used already by RemedialCS to repair cracked brickwork. Deformed bar is bonded into a rebate cut in a horizontal mortar bed across the crack line.

Repair Cracked Slab

In the case of a cracked slab, I recommend either stainless steel deformed bar from Valbruna or an epoxy coated bar because the reinforcement won’t have much cover and we don’t want the reinforcement to rust.

Butterfly stitch across slab crack

Depending on the application, grind 10mm x 50mm deep x 300mm long trenches perpendicular to the crack at 600mm to 1000mm centres. Place a bed of epoxy mortar in the trench, insert the stainless steel deformed bar in the trench and then fill the rest of the trench with epoxy grout.

Repairing cracked concrete
New crack stitches being installed

Once the tiles are placed over the repaired area, you’ll never know the butterfly stitches are in.

Cracks in Precast Concrete

We’ve specified a similar treatment for a precast panel that had cracked when it was lifted from the precast bed. The crack closed back up when the panel was in position so construction progressed, but the principal rejected the panel with the crack. The principal accepted butterfly stitches across the crack as a repair methdology and the work was completed on the vertical wall panel without removing it from service.

What Else Can We Fix

So there you have it. Butterfly stitches aren’t just for medical emergencies. You can also use them to help hold closed cracks in concrete and brickwork.

If you have a cracked slab, precast panel or brickwork wall, maybe butterfly stitches will help you. Call Cornell Engineers for an assessment and advice on how best to repair your cracked concrete or masonry surface.