Laitance
The weak, fine layer of cement and fines that rises to the surface of concrete as it cures and bleed water evaporates. It looks like sound concrete and has almost none of its strength.
On an actual building
Anything bonded to laitance is bonded to a layer that will itself detach. Removing it mechanically is the first step of nearly every waterproofing job, and skipping it is the most common cause of a system debonding within a year or two.
What we most often have to correct
That washing the slab is enough. Laitance is removed mechanically — by grinding, scabbling or blasting — not by hosing it down.
Terms that come up alongside this one
- Bond Coat
A slurry, usually waterproofed cement, brushed hard into a prepared substrate so that the layer above bonds to it monolithically rather than sitting on it..
- Curing
Keeping cementitious material adequately moist and at a suitable temperature while it hydrates and develops strength and impermeability..
- Primer
A preparatory coat applied to a substrate to seal it, improve adhesion and provide a compatible surface for the system that follows..
Laitance — questions we get asked
What does laitance mean in waterproofing?
The weak, fine layer of cement and fines that rises to the surface of concrete as it cures and bleed water evaporates. It looks like sound concrete and has almost none of its strength.
Why does laitance matter on a real project?
Anything bonded to laitance is bonded to a layer that will itself detach. Removing it mechanically is the first step of nearly every waterproofing job, and skipping it is the most common cause of a system debonding within a year or two.
What do people commonly get wrong about laitance?
That washing the slab is enough. Laitance is removed mechanically — by grinding, scabbling or blasting — not by hosing it down.
Have a building showing this?
If a term on this page describes something you are looking at, a site inspection will tell you how far it has gone and what it needs. It costs nothing.
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