Question 1

What wall thickness should I choose?

Accepted Answer

200 mm for internal partitions. 300 mm for external walls in a temperate climate with added insulation. 400 mm for external walls without insulation in a mild climate. In cold regions, use 400–500 mm, or 300 mm plus an insulation layer.

Question 2

Aerated concrete or foam concrete?

Accepted Answer

Autoclaved aerated concrete has a uniform structure, precise dimensions, better thermal insulation and higher strength. Foam concrete is cheaper but has poorer geometry and a lower grade. For load-bearing walls, aerated concrete is the clear choice.

Question 3

Do I need a reinforced bond beam?

Accepted Answer

Yes — under floor slabs, under the roof wall plate, and at every storey level once the house exceeds 6 m in height. Aerated concrete performs poorly in bending, so a reinforced-concrete bond beam spreads the loads.

Question 4

How do I account for door and window openings?

Accepted Answer

Subtract the area of windows and doors from the total wall area before you calculate. A standard window of 1.2 × 1.4 m = 1.68 m²; a doorway of 0.9 × 2.1 m = 1.89 m². Don't forget the lintels above the openings.

Question 5

Why a 5% waste margin and not 10%?

Accepted Answer

Aerated blocks are large and cut cleanly with an angle grinder or saw, so cutting losses are minimal and broken blocks are rare. Brick uses a higher margin (10–15%) because the small format produces far more offcuts.

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