How to extend height of boundary wall?

Claire_Marie

There is this block wall (see photo) on the boundary, which is 21m long. We would like to increase the privacy by adding some height to it, but I imagine that adding 4 rows of blocks over 21m would be quite expensive.

Does anyone have an idea of how else we could extend the height of this wall (by approx. 1m) in a more affordable but attractive way? We could get someone to do it, it doesn't have to be DIY, but I'd need to give them an idea.

Many thanks
Colette

MitchellMc

Hi @Claire_Marie,

Raising the height of the existing block wall by another metre is certainly possible, but the cost does not usually come from the blocks themselves. For a wall of around 21 metres, the actual blocks might only cost in the range of a few hundred dollars, roughly around $500 if your photo shows the full length. The bigger issue is that the wall you have now was likely designed and engineered to be only that height. Lower retaining or boundary walls are often not core‑filled with concrete or reinforcing bars, and may not sit on a footing strong enough to safely support significant extra height. Once you need to retrofit reinforcement or upgrade the footing, the cost can increase very quickly and often becomes more expensive than building a separate structure.

A practical alternative is to keep the existing wall exactly as it is and extend the privacy height above it using a lighter material. One option is to attach vertical treated‑pine or steel posts along the wall and then clad over those with something like merbau screening or other timber battens. This approach avoids altering the structural role of the lower block wall while still giving you the extra metre of privacy you want. The material cost for timber screening is usually higher than concrete blocks, but it avoids the engineering complications and is typically far more straightforward for a contractor to install.

This kind of add‑on extension also allows for a softer and more decorative look, and it avoids the risk of overloading a wall that may not have been designed for additional weight. I’ve put together the rendering below to help illustrate the idea and how a timber screening extension would sit above your existing blocks. I've also produced an AI image of a more upmarket approach, thought the cost would be higher.

Please let me know if you have any questions.

Mitchell