Question 1

What are the coverage rates for different exterior surface types?

Accepted Answer

Coverage rates vary significantly by surface texture. Smooth wood covers the most area at 9 m²/L. Rendered surfaces are next at 8 m²/L. Rough stucco reduces coverage to 7 m²/L due to the textured surface absorbing more paint. Brick and masonry require the most paint at only 5 m²/L — their porous, uneven surface soaks up considerably more paint than smooth surfaces.

Question 2

How many coats of paint do exterior surfaces need?

Accepted Answer

Two coats are strongly recommended for exterior surfaces. The first coat seals the surface and provides adhesion, while the second coat delivers full colour and weather protection. A single coat leaves surfaces vulnerable to UV damage, moisture, and cracking — which can lead to costly repaints within 2–3 years. On bare or heavily weathered surfaces, a primer coat before painting may also be needed.

Question 3

How do I measure the total exterior wall area?

Accepted Answer

For a simple rectangular building, multiply the perimeter by the wall height: perimeter = 2 × (length + width). For example, a 10m × 8m building with 3m walls has a perimeter of 36m and wall area of 108 m². Subtract door and window areas if you want a more precise estimate — typically 2 m² per standard window and 2 m² per door. This calculator uses the total area you provide, so you control how much you subtract.

Question 4

What waste factor should I use for exterior painting?

Accepted Answer

A 10% waste factor is standard for most exterior projects. For rough, textured surfaces like stucco or render, consider increasing to 15% as the coverage rate is already reduced and spray or roller absorption can vary. For very large or complex facades with multiple angles, 15–20% provides a safe buffer. It's generally better to have extra paint for touch-ups than to run short.

Question 5

Should I use a different calculator for interior walls?

Accepted Answer

Yes — this calculator is designed for exterior surfaces (Brick, Wood, Stucco, Render). For interior rooms, use the Room Paint Calculator which computes wall area automatically from room dimensions, or the Paint Coverage Calculator for full control including ceiling, doors, and windows with interior paint types.

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