Building services — recommended outward slope for verandah floors (drainage fall) For proper drainage away from the building, what outward slope is commonly recommended for verandah floors?

Introduction / Context:
Horizontal exterior surfaces adjacent to buildings must be detailed with a slight fall to shed rainwater quickly and prevent water ingress. Verandahs, being semi-external, need a clear outward slope for drainage and slip safety.

Given Data / Assumptions:

• Standard ceramic/stone/trowelled finishes on verandah floors.
• Moderate rainfall conditions.
• Conventional practice without special drainage channels.

Concept / Approach:

A fall of about 1 in 40 is widely used for verandahs and balconies—steep enough to move water off the surface rapidly, yet gentle enough for comfortable walking and furniture placement. Flatter slopes like 1 in 60 or 1 in 100 may leave lingering puddles; steeper slopes can be noticeable underfoot and complicate thresholds.

Step-by-Step Solution:

Verification / Alternative check:

Manufacturer guidance for exterior tiles and balcony standards commonly recommend falls in the 1:40–1:60 range; 1:40 is a robust choice for verandahs.

Why Other Options Are Wrong:

• Flatter slopes (1:50 to 1:100) risk ponding depending on finish tolerance.
• Steeper slopes than 1:40 are uncommon for general verandahs unless required by site conditions.

Common Pitfalls:

• Laying finishes without check screeds—actual slope may end up flatter than intended.

Final Answer:

1 in 40.