Laitance
Laitance: weak surface layer of cement and fine particles on concrete or screed. Must be removed before tiling, adhesive fixing, or waterproofing membrane application.
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Laitance is a weak, chalky surface layer that forms on freshly placed concrete or cement screed as fine cement particles and water bleed to the surface during curing. It produces a friable, powdery finish with poor mechanical strength and poor adhesion.
Laitance must be removed before applying tile adhesives, waterproofing membranes, or any bonded finish. If left in place, the finish bonds only to the laitance layer rather than the substrate proper, and bond failure follows. Removal methods include mechanical grinding, scarifying, or shot-blasting; acid etching is used on smooth cast surfaces. Per AS 3958:2023, substrate surfaces must be clean and sound before tile adhesive is applied.
Also known as: surface laitance, cement laitance.
Category: Substrate preparation, tiling.
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Last updated: 2026-05-10. Verified: 2026-05-10. Quarterly review for currency.