In building measurement, damp-proof course (D.P.C.) installed in walls is measured for payment under which unit of measurement?

Introduction / Context:
Damp-proof course is a thin barrier layer (e.g., polymer-modified bituminous membrane, rich cement mortar with additives) laid horizontally in masonry to block capillary rise of moisture. Correct unit selection in measurement ensures alignment with standard rates and avoids ambiguity in tendering and billing.

Given Data / Assumptions:

• D.P.C. is a thin layer of nearly uniform thickness under wall lengths.
• Thickness is specified, but the payable quantity primarily depends on covered area.
• Standard schedules treat such items similarly to floor or surface treatments.

Concept / Approach:
Because D.P.C. is not a volume-intensive item like concrete nor a simple linear accessory like a beading, its measurement is generally on an area basis. The unit therefore is square metre (Sq m), with the thickness and composition defined in the item description (e.g., 25 mm thick 1:2 mortar with waterproofing compound or a membrane specification).

Step-by-Step Solution:
1) Identify that D.P.C. covers a plan area under walls.2) Record length × width (or wall thickness) to compute area.3) Apply the specified thickness and material in the item description; unit for payment remains Sq m.4) Note any laps, overlaps, and turn-ups as per specification—often included in the area measurement.

Verification / Alternative check:
Schedules of rates list D.P.C. with rate per Sq m, reinforcing the area-based measurement convention.

Why Other Options Are Wrong:

• Cub.m: Used for volumetric items (concrete, earthwork), not thin layers.
• Metres: Suits linear items (beading, expansion joints), not area spreads.
• None of these: Incorrect because Sq m is standard.

Common Pitfalls:

• Measuring D.P.C. by wall centre-line length only, forgetting to multiply by thickness for area.
• Ignoring overlaps/returns required by specification.

Final Answer:
Sq m.