Floating is the masonry and plastering action of pressing freshly applied mortar or plaster firmly into joints or against a substrate and finishing it flat with a tool. The aim is to obtain a dense, well-bonded layer free of voids, shrinkage cracks or poor adhesion.
How to float mortar
The technique varies by application:
- Pointing — the pointer presses pointing mortar firmly into the joint with a jointing tool, squeezing out air and forcing the mortar into intimate contact with the bricks
- Plastering — the plasterer ‘floats’ the skim coat with a float or felt pad, compacting and smoothing the surface
- Floor finishing — fresh concrete is floated with a power trowel (hand or ride-on) until the surface is smooth and closed
Why float?
- Denser structure — less porosity therefore less water penetration
- Better adhesion — mortar mechanically keys into the substrate
- Flat finish — no bumps or holes
- Stronger surface — a floated finish has more wear resistance
- Attractive appearance — fine, closed surface with no visible tool marks
Applications
Floating is used for:
- Pointing — facades, chimneys and historic masonry
- Plastering — smooth interior walls
- Concrete floors — industrial floors, parking garages and warehouses
- Cement screeds — to provide a flat substrate for tiling
- Restoration — bringing back historic lime and trass mortars
Tools for floating
| Application | Tool | Action |
|---|---|---|
| Joints | Jointing tool / pointing iron | Press firmly into the joint |
| Plaster | Float, felt pad | Circular motion to compact |
| Concrete floor | Power trowel (hand or machine) | Rotate flat across fresh concrete |
| Patching | Trowel, finishing tool | Press in mortar and strike off |
Points to watch
- Timing — the mortar must not yet have set but must already be stiffening; too early gives slurry, too late gives cracks
- Moisture — too dry a substrate sucks out water and prevents bond
- Don’t over-work — excessive floating brings water to the surface (bleeding) and weakens the finish
Related terms
- Pointing
- Plastering
- Mortar
- Trowel
- Power trowel
- Float
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