Plastering practice: The process of filling hollow spaces, voids, or deep depressions in masonry walls before applying the plaster coat is called

Introduction / Context:
Before plaster is applied, uneven masonry often contains hollows, wide joints, or recesses that would otherwise lead to variable plaster thickness. The preparatory operation to make the surface reasonably true and to control plaster thickness is essential for durability and a smooth finish.

Given Data / Assumptions:

• Masonry wall background with localized hollows, chases, or depressions.
• Objective: prepare a true surface so the plaster coat has uniform thickness.
• Terminology being tested: hacking, dubbing out, blistering, peeling.

Concept / Approach:
“Dubbing out” refers to filling hollows and deep depressions with compatible mortar before the main plastering operation. This creates a uniform substrate and avoids overly thick patches that are prone to cracking or falling. “Hacking” is different: it is roughening/indenting the background (often with a hacking tool) to improve mechanical key for mortar. “Blistering” and “peeling” are defects observed after finishing and are not preparatory operations.

Step-by-Step Solution:
Identify the task: fill hollows before applying the main plaster.Match the operation to standard terminology → “dubbing out.”Differentiate from “hacking” (roughening), “blistering” (bulging defect), and “peeling” (loss of adhesion).Conclude that the correct term is “dubbing out.”

Verification / Alternative check:
Site specifications often require dubbing out in two or more passes for deep hollows, allowing partial set between passes to limit shrinkage, followed by a scratch coat and finishing coat.

Why Other Options Are Wrong:
Hacking: surface preparation by roughening, not filling hollows.Blistering: a defect after finishing; not a preparation step.Peeling: detachment of paint/plaster layers; not a preparation step.All of the above: incorrect because only “dubbing out” matches the definition.

Common Pitfalls:
Skipping dubbing and applying a thick single coat; failing to allow intermediate set; using too rich a mix that shrinks and cracks.

Final Answer:
Dubbing out (filling hollows before plastering).