Question

The different parts of a parapet wall and terrace section are labelled as P, Q, R, S, T. Which of the following is/are correct?

• A. P - Coping, R - Lime terracing, S - Rainwater pipe
• B. Q - Drip course, S - Rainwater pipe, T - Roof slab
• C. P - Vent pipe, Q - Drip course, R - Roof slab
• D. P - Vent pipe, R - Rainwater pipe, T - Roof slab

Hint:

Work top to bottom on the parapet section: P = coping, Q = drip course, then the terrace build-up (R = lime terracing over T = roof slab), and S = rainwater pipe at the outlet.

Answer 1

The Correct Option is A, B

This figure is a standard parapet-and-terrace detail, and the fastest way to solve it is to fix the top-most label first and work down, since P being wrongly called a vent pipe in two of the four options is the easiest trap to spot.

1. Option (A): P - Coping, R - Lime terracing, S - Rainwater pipe: P is the topmost, projecting, weather-throwing element of the parapet, which is exactly the coping. R points into the sloped, graded fill above the roof slab, which is the lime terracing that gives the roof its drainage fall. S sits at the pipe bend carrying water off the roof, the rainwater pipe. All three checks pass, so (A) is correct.
2. Option (B): Q - Drip course, S - Rainwater pipe, T - Roof slab: Q sits just under the coping on the wall face, which is where a drip course is built in to stop water tracking back along the underside of the coping. S is again the rainwater pipe, already confirmed. T points to the structural layer at the bottom of the terrace build-up, the reinforced concrete roof slab itself. All three checks pass, so (B) is also correct.
3. Option (C): P - Vent pipe, Q - Drip course, R - Roof slab: this option calls P a vent pipe, but P is at the very top of the wall on the coping, nowhere near a vent pipe, so this option is wrong regardless of its other claims.
4. Option (D): P - Vent pipe, R - Rainwater pipe, T - Roof slab: this again mislabels P as a vent pipe, and also swaps R, which is lime terracing and not the rainwater pipe, so this option is wrong on two counts.

Both options that respect the coping at the top of the parapet turn out to be fully correct, while both options that mislabel P as a vent pipe fail immediately.

Let's summarize:

• P is the Coping at the top of the parapet, Q is the Drip course just below it
• R is the Lime terracing over T, the Roof slab underneath
• S is the Rainwater pipe that carries water off the roof

So the correct options are (A) and (B).