Under concrete floors, how many inches of grillage must be on the top, bottom, and sides of the pipe?

Under concrete floors, how many inches of grillage must be on the top, bottom, and sides of the pipe?

• A. 4 inches
• B. 6 inches
• C. 2 inches
• D. 3 inches

Answer: (A)

When a pipe runs under a concrete floor, it needs a protective encasement to resist the weight of the slab and any ground movement. That encasement is called grillage, and the standard minimum is four inches of concrete cover on all sides of the pipe—top, bottom, and both sides. This uniform 4-inch surround distributes loads evenly and helps prevent the pipe from being crushed or damaged over time, while still allowing the slab to bear normally. So four inches on every side is the correct requirement, ensuring adequate protection without adding unnecessary extra thickness. Options with less than four inches wouldn’t meet the protection standard, while more than four inches isn’t required by typical practice.

When a pipe runs under a concrete floor, it needs a protective encasement to resist the weight of the slab and any ground movement. That encasement is called grillage, and the standard minimum is four inches of concrete cover on all sides of the pipe—top, bottom, and both sides. This uniform 4-inch surround distributes loads evenly and helps prevent the pipe from being crushed or damaged over time, while still allowing the slab to bear normally.

So four inches on every side is the correct requirement, ensuring adequate protection without adding unnecessary extra thickness. Options with less than four inches wouldn’t meet the protection standard, while more than four inches isn’t required by typical practice.