Another cracked wall question

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Chris Hogg 5 years ago

I have a low garden wall retaining a raised bed. It's been there since

1960. The lower bed was heavily overgrown when I inherited it and I've only recently cleared back the shrubs and exposed it. It has a substantial crack running from top to bottom. One side of the wall is moving outwards. I don't know how long it has been going on, nor whether it has stopped. Pictures here:

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and

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My first job is to see if it's still moving, using the 'microscope slide' method. I don't have any microscope slides, but I do have a narrow strip of glass recovered from a Dutch Light greenhouse pane. At

2.9mm thick, it's probably thicker than a microscope slide; at 3.5cm, it's also a bit wider. Length can be whatever's needed. Would this be an OK substitute? If so, how do I fix it in place. I don't have any mortar. Would Araldite be OK or would it 'give' too much? What else?

If it is still moving, what's the best way of stopping it? If I clean out the gap, would a crack repair grout such as Harry suggested in the previous thread kit be suitable?

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I have thought of tackling it from both sides, by digging down through the upper bed to expose the crack on that side.

Any other suggestions welcome.

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Chris Hogg 5 years ago

Looks like it, but I've no idea as to the history.

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Andrew 5 years ago

You could 'acquire' a 3 foot length of scaffolding and hammer it into the ground behind the section that is cracking, then dig away some of the soil that the wall is holding back and tip a couple of buckets of concrete mix in so that the scaff pole is surrounded and the concrete manages to attach to the two bits of wall.

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Vir Campestris 5 years ago

Araldite will be perfect. Once set it's completely inflexible.

That wall though... I wonder if it was once dry stone? That's some of the worst pointing I've ever seen!

Andy

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Brian Gaff (Sofa) 5 years ago

Any tree roots around and about that area? Is the underlying soil clay based in the he main perhaps? Brian

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Martin Brown 5 years ago

Looks to me like that wall is less than 18" high.

I wouldn't be too concerned about its risk of falling down. Cosmetic repair I'd be inclined to remove any loose stones and repoint with a lime rich mortar that will be more tolerant of slight movement.

When you get to 2' or more the risk of a wall collapsing becomes much more serious since it can do real damage to anything it falls on.

Araldite is probably good enough but you can get nicer two part tell tales made of perspex and attach one to either side. One is a bulls eye with a dot in the middle and the other a vertical and horizontal grid. Allows you to track movement or not in a quantitative way longer term.

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A DIY one using a school geometry set should be easy enough. They work best on nice smooth brick so could be a challenge on rough stone!

At that height and in that position I wouldn't be worried. YMMV

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Chris Hogg 5 years ago

No, it's ~2'9". I should have put a rule against it when I took the photo.

Ah! That's useful. Thanks. Another one I found says it can be fixed in place with Araldite, so I imagine this one can as well.

Perhaps I can butcher an old Perspex ruler and overlap the mm scale, back to back.

Especially as the displacement is outwards rather than sideways, IYSWIM. I can see a generous application of Araldite being necessary!

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Andrew 5 years ago

If it is decent stone then proper lime mortar should have been used which would have accomodated some movement.

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