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How to build a block wall?

Hi all 😀

so I'm building a block wall, first time!; got some question

beside the sub-flooring compacting..

wall will be 1m in height with 2.4m intervals with pillers at 2m height upto 40m long; how deep the trench should be? and how high should concrete be filled with L rebar ?

and

Brighton Masonry 390 x 190 x 190mm Full Besser Block or Hebel PowerBlock 600 x 200 x 100mm - 100/PLT ?

Thanks

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Comments

MitchellMc

Hi @mitc69,

If this wall is going at the front of your property, it’s worth checking in with your local council first to make sure it complies with any local height, boundary, or aesthetic regulations and to also determine is a wall of this size needs approval and engineer documentation provided for it. It would also be a good idea to have a chat with a qualified builder—even just to talk through your plans. Pillars up to two metres tall can pose a real safety risk if they’re not properly designed and built.

Hebel PowerBlocks are lightweight aerated concrete blocks, so they’re easier to lift and work with than traditional concrete blocks. They offer good thermal and acoustic insulation, but they’re not as strong when it comes to load-bearing or retaining. Hebel walls should be laid on a flat, reinforced concrete footing, typically around 300mm wide and at least 150mm deep, though you’ll want to check Hebel’s installation guide for your specific application. The blocks are bonded with Hebel Adhesive, and steel reinforcement rods are often run vertically through core holes for stability, especially if the wall is over a certain height or exposed to wind.

Besser blocks are more traditional and structurally robust, especially for structural or retaining walls. These should be laid on a properly compacted sub-base with a reinforced concrete footing—often around 400mm wide and 200–300mm deep depending on soil type, wall height, and whether it's freestanding or retaining. L-bars (L-shaped steel rebar) are typically set into the footing at your pillar locations and at regular intervals (often matching your core fill pattern) to tie into vertical reinforcement within the block cores. These cores are then filled with concrete for strength. Here's the Technical Guide for Besser blocks.

For a 1m high wall with 2.4m spans between 2m high pillars, it sounds like you'll need reinforcement in both the wall sections and the pillars. Depending on your soil and wind conditions, a trench depth of around 400mm might be appropriate, filled to at least 300mm with reinforced concrete, but you should consider getting some engineering advice for a wall of this scale—especially to work out your reinforcement spacing and footing depth properly.

Please let me know if you have any questions.

Mitchell

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