Finishing, Curing, and Quality Control
This domain tests surface preparation, plastering or rendering, pointing, curing, and inspection of masonry finishes. The exam expects control of thickness, flatness, plumb, joint finish, and curing time, plus recognition of defects before they are covered up.
Core rules
- Prepare the surface: remove loose mortar, dust, and oil, and dampen absorbent masonry before plastering.
- Apply plaster or render in the specified thickness and number of coats; do not build too thick in one pass.
- Cure cement-based finishes by keeping them moist for the specified period, commonly about seven days, and protect them from direct sun and wind.
- Check finished work for plumb, level, flatness, joint thickness, and honeycombing.
- Repair defective areas with compatible mortar after cutting back to sound material.
- Record inspection results and do not paint or seal before the masonry is dry.
Worked example
A 15 mm plaster coat is specified. The wall is dampened, a scratch coat is applied and cured, then the finish coat is brought to the required thickness using guides. For seven days the plaster is misted or covered to keep it moist. The reasoning is that cement needs moisture to gain strength; rapid drying causes shrinkage cracks and a weak surface, even if the plaster looks dry and hard.
Traps
- Adding water to a plaster mix to make it easier to spread after it stiffens.
- Applying a thick coat in one pass to save time.
- Skipping curing because the surface looks dry.
- Painting over damp masonry or efflorescence.
Key points
- Prepare and dampen the surface before plastering.
- Apply the specified thickness and number of coats.
- Cure cement finishes with moisture for the specified period.
- Check plumb, flatness, and joint finish.
- Do not paint over damp masonry.