garden wall

Last summer we built a 60cm high garden wall. For this, we dug a small foundation and filled 2.5 of the total 3 rows of hollow concrete blocks with concrete. Additionally, we hammered in a reinforcement bar every meter, which is supposed to provide extra stability for the wall. The top row of the wall we finally filled with potting soil and planted accordingly.

It looked so good until this winter when the middle row completely, stone by stone, got frost damaged. I suspect it was due to the cold and the moisture in the concrete. What did we do wrong? The concrete was not mixed by hand, but thoroughly mixed using a rented concrete mixer, and we always paid attention to the mixing ratio. For mixing in, we used sand/water and ordinary construction cement.

I thank you in advance for your suggestions.

Hello grisu77,

From a distance, it is not really possible to assess this properly. Technically speaking, the time from summer to winter was sufficient for the concrete to cure. Since the top row of stones served as a flower trough, watering was also done - water was added. This water probably found its way into the lower row; for example, through fine cracks in the concrete. The water freezes, expands, and the stones burst. If you rebuild the wall, place a layer of bitumen membrane between the "flower stones" and the row below so that no water can penetrate anymore. So, in reverse order, you renew the damaged row, lay a strip of bitumen membrane on it, and then build the stones for the flowers.

I don't know how much space you have, but here I simply built a slightly thicker wall and then directly "masoned" terracotta bowls onto it (yes, I know, not professional language). It actually works quite well and hasn't caused any problems so far.