Some advice with regards a retaining dry stone wall

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Will Hay

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Hi all,

new member here seeking advice from you more experienced guys.

In about 2006/ 2007 I had to get a retaining wall built at the back of my garden as the ditch was collapsing in sections into the garden especially during really wet weather. Eventually managed to find a person willing to tackle the job

First set of photos show the initial work digging out foundation and a picture show the finished article in 2006/2007 - The job was good even though at the time I did wonder would it not have been better to put a wall (block on flat) behind the dry stone wall but the guy didn't he just built the dry stone wall as you can see there.









IMG_3712.JPG
 
So presumably the wall is failing now, so basically yes the guy should have built some blockwork behind the stone on a suitable base, a rough rule of thumb for mass retaining walls is that the thickness at the base should be about 1/3 of the height.
 
So the guy who built the wall was quite elderly and probably shuffled off his moral coil

This is what I have left to deal with - there are some visible cracks in the wall you may see from the photos and also a section by the patio area is sagging


Do you guys think this wall needs to be fixed or will it stay up for next 10-15 years?




Trying to get the best and cheapest (!!) fix for this

Was thinking of a gabion structure in front of the existing wall but this would probably shift as the wall bulges further, right? or would that work?

Next someone mentioned buttress so some columns at right angles to the wall

Another possibly is wall anchors but I don't know if these would hold.

Someone else mentioned maybe leaving it collapse and banking up the area



I don't know the best option so looking for some guidance, any help is appreciated
 
The wall you have now is not a dry stone wall, it has mortar. Also it would have been a good idea to build it with a significant slope back from the base, currently it is sloping the wrong way. How deep (front to back) is the base?
This and others on the same site are dry-stone walls:

Altman Court Steps & Retaining Walls ⨳ Arabella Stone

Altman Court Case Study by Arabella Stone. We were contracted by MN Green to complete some specialty stonework for this new construction build. The expansive property showcases beautiful stone patios, drystone retaining walls and natural stone steps.
arabellastone.com arabellastone.com
 
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Mike13 said:
The wall you have now is not a dry stone wall, it has mortar. Also it would have been a good idea to build it with a significant slope back from the base, currently it is sloping the wrong way. How deep (front to back) is the base?
This and others on the same site are dry-stone walls:

Altman Court Steps & Retaining Walls ⨳ Arabella Stone

Altman Court Case Study by Arabella Stone. We were contracted by MN Green to complete some specialty stonework for this new construction build. The expansive property showcases beautiful stone patios, drystone retaining walls and natural stone steps.
arabellastone.com arabellastone.com
Click to expand...
Apologies for wrong description, there is no slope as you mentioned it is upright.

The base is about 18" I'd guess

Does this wall need to be addressed? From your opinion will it collapse at some time?
 
It will collapse some time, I have no idea if it will be this year or 10 years. Usually there will be warning, but there might not be, and that could injure people quite badly. a 10+ kilo stone falling from 2 metres onto you is going to give you a very bad day.
A 45cm base is ok for up to 1.5 metres if made well. It should have the top set back noticeably from the base, if it is 20cm at the top, then the top front should be at least 20 cm from the bottom front, if not 30cm or so slope. That way the wall tries to fall away from you and the earth behind cannot fall out onto you. If you trawl around that site above he discusses some of the mechanics of a dry stone wall that are also applicable to a mortar and stone wall.
It may be the angle you took it from, but it looks like the top is further over than the bottom, if you put a spirit level against the wall is it sloping away from you or towards you. Make a note of how much slope you have and recheck it every now and again, that will tell you if it is currently moving. You also need to consider the soil in your area that is behind it, check with neighbours about how sandly/clay filled etc, it makes a difference to how much it softens when really wet.
 
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Ok folks here is an update on this ….

Had a civil engineer who called today to view the wall and agreed that it will fall in 5 days , 5 months or 5 years hard to tell but he could see where it will break through

He came with two suggestions

Suggestion 1 - remove wall and dig a huge and wide foundation and a proper wide wall to the cost of about €20,000 and that should stay up for 300 years

Suggestion 2 - a gabion structure in front to prevent movement with a wide base as in two gabion cages wide - would be cheaper but price don’t know yet


What do you folks think ?

Would a gabion hold back the wall ??
 
For sure it will, a gabion will deform as the wall gradually continues to bow outwards but pretty unlikely to collapse in any catastrophic way.
 
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