Category: Finishes
Prepared by Eng. Ahmed Fathy, Projects Manager ·
Definition
Plaster is a layer of cement mortar applied to walls and ceilings to level, protect and prepare them for paint or cladding. It is usually applied in two coats: a spatterdash coat then a render coat.
Why it matters on a project
The straightness of the plaster sets the quality of everything after it; any lean or wave shows clearly under paint and lighting.
Measurement and pricing
Measured in square metres with large openings deducted; corner beads are sometimes measured in linear metres.
Worked example
A 4 × 5 m room 3 m high: perimeter 18 m × 3 = 54 m², less the openings the method of measurement says to deduct.
Common mistake
Plastering without mesh where blockwork meets concrete, so hairline cracks appear along the joint.
Frequently asked questions
How thick is internal plaster?
Usually 15 to 20 mm for both coats, more where it makes up for an uneven wall.
When can I paint after plastering?
Once it is fully dry; the time depends on thickness, weather and ventilation.
Related terms
- Putty (skim coat)A thin smooth layer over plaster preparing the surface for paint.
- Emulsion paintWater-based paint for internal walls and ceilings, in various sheen levels.
- Surface preparationCleaning a steel surface to a specified grade (e.g. SSPC-SP 10) before coating to ensure adhesion.
- Expansion jointA joint allowing the building to expand and contract thermally without cracking.
Read next
- Work out quantities with our free calculators: concrete, tiles, paint and plaster. Open the calculators
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