A carpenter is preparing to set up the formwork for a building's strip footings. The site has been excavated, and a layer of granular fill has been placed and compacted. What is the main reason for placing a 'mud slab' or 'working slab' (if required by design) directly on the granular fill before setting footing forms?

Question: A carpenter is preparing to set up the formwork for a building's strip footings. The site has been excavated, and a layer of granular fill has been placed and compacted. What is the main reason for placing a 'mud slab' or 'working slab' (if required by design) directly on the granular fill before setting footing forms?

Answer options:

• To serve as a permanent waterproofing layer ✅ To provide a clean, level, and stable surface for rebar placement and formwork setup
• To increase the overall bearing capacity of the soil
• To insulate the footings from frost penetration

Correct answer: To provide a clean, level, and stable surface for rebar placement and formwork setup

Explanation: A mud slab (or working slab) provides a clean, level, and stable surface, which simplifies the accurate placement of rebar and the construction of footing formwork on uneven or soft subgrade conditions. It is not its primary role to waterproof, increase bearing capacity, or insulate, though it can offer minor incidental benefits.