Crack re appearing in breeze block exterior garden wall

miketurner · 26 Aug 2019

I had wall built and the outside face was then rendered (the inside is not seen and has bushes up against it, so that side was not rendered).

it’s breeze block exterior garden block wall around 4 feet high and around 30 feet long with expansion joints (please see photos) built around 2 years ago.

After about a year it seems to have developed a vertical stepped shaped crack on the outside of the wall.

I think it is breeze block (although not sure) and I dug out the crack and filled it with exterior filler. After 6 months the crack has re appeared so I started again and used Toupret exterior filler to repair the crack.

I also put some filler on the side of the wall which is not rendered, just in case there was a crack and water was getting in on the inside.

Now some 6 months later again the crack has re appeared. A friend said maybe when it was built one of the blocks may have cracked but the builder just rendered over the top of it, although I’m not sure if this is the case.

Can anyone suggest what I can do to stop repair the wall and stop this crack re appearing as this is my 3rd attempt to cure the problem ?

ILikeDIYS · 26 Aug 2019

Make the crack bigger then fill with exterior rated flexible tile adhesive (from powder). Paint over.

tony1851 · 27 Aug 2019

Free-standing walls should not be rendered; not only does it create an imbalance between faces, it traps ground moisture in which can cause problems.
The wall also looks to be single-block thickness (?). If so, it's very thin for its height.

miketurner · 27 Aug 2019

Hi
It has a post at each end and also curves at one end and has intermediate posts on the inside so I’m not worried about that issue. My other similar wall which is exactly the same has no problems.
Can anyone help further

H2Gizmo · 6 Sep 2019

Remove all the render, . obtain galvanised metal lath mesh sheet from wickes for example and fix it to blockwork with galv screws. Render back over. It's the same principle as using fibreglass scrim for internal plastering on joints.. It's not fool proof but the best outcome u will achieve as expanding tubes of this that and the other do not work. This is for vertical and horizontal cracks, where drying out shrinkage is occurring as externally the blocks and render soak up the moisture and dry out again in our weather. For angled cracks.. This is related to the foundations and movement... That's entirely a different subject .

miketurner · 6 Sep 2019

Thanks HZGizmo, I will give that a go.

tony1851 · 7 Sep 2019

I think galvanized mesh will soon rust through; over time, cement mortars and renders become slightly acidic, which attacks the zinc and exposes the steel to rust - that's why galvanized wall ties are now not used, but have been replaced by stainless steel ties instead.

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Crack re appearing in breeze block exterior garden wall

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