If you've ever built a random stone retaining wall you've probable constructed an internal skin in either hollow concrete block or a single skin of engineering type brick.
Construction is relatively easy using this method. Build up the block work or brickwork, leave to go off and then use this rigid structure to retain the mortar as the stone face is built up in front of it.
Using a string line's an easy way to build a face that is true maintaining a consistent width and as long as you don't work too fast.
What if you have to build both the back and front face in stone?
First of all, depending on the porosity of the stone you are working with you cannot bump up too high in one go as the mortar may slump and push out the face of the wall.
If you have a long wall to build then it's easy to spread the build giving each section a sensible amount of time to allow the mortar to go off before bumping up the height further.
There is also the need to construct both faces fairly simultaneously so when you fill the void in the centre (I always use rubble or old tile rather than just cement - the mortar cannot be allowed to slump and push the faces of the wall out).
Random stone comes in many shapes and sizes (hence the name;) Sometimes there is not a discernible face so using a string line, but also standing back and taking a view is essential. Sometimes you may have to compromise on precision to attain the look you require.
Random walls also have no horizontal courses.
To maintain the right width as I bump up my wall I use a simple wooden profile at each end of the wall with a notch, cut into each side of the profile, at the required width of the wall. This way I only have to concentrate on setting up one face (usually the one most visible) and the other one is then automatically parallel.
String lines are tensioned between the two wooden profiles and raised up with the wall. In this example I am using stone corners to create a rigid end but this method is also effective if the ends are random stone too.
The stone wall below will only actually have one visible face but because I have an awful lot of old tile, concrete and stone I cannot use for facing I'm building the whole wall using this method.
fig 1. A notched wooden profile is used the gauge the faces of the wall at 40cm wide. Align the string line with the face and the rear string line will automatically be spaced.

Fig 2. Make a corresponding mark on the profile and the stone so you can realign if you need to take down your string line. Repeat this process every time you bump up an end or corner.

Figure 3. Note how the rear string profile. It's impossible to get the width wrong using this method.

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Here's this section of wall completed. Note most joints have no mortar. Mortar is only really used in the centre or if used as a joint then it's not allowed to squeeze through and become visible. I do this to keep the building method as authentic as possible.
My farmhouse was built by peasants: probably even by the farmer himself, together with his family. Joints are mud and the stone quarried on site and hauled no more than 200 metres from the house. The house itself is built directly onto the bed rock and therefore doesn't have a footing. You can just see in the the photo below how part of my garden wall is built directly onto rock.
I may at some stage crépie (joint) the stone face but I really like the texture and shadow this method creates.
I like this post, someone has been listening and thank you.
Thats a nice looking wall, looks good.
This is something i am working on at the moment, 35 meters curved stone facing wall.
I just wish the rain would stop so i can carry on.
I know what you mean Phil about compromising on precision.
Thanks Tim:)
Busy Bee Garden Services Limited said:
Look forward to seeing the finished wall Dan.
A D Landscapes said:
Is that part of the bedrock in the centre of your wall Jez?
Jez Young said:
Phil Voice said:
As one who usually leans the faces of his walls inwards ( deliberately I might add for dry stone walls) I find it very difficult to build a wall with a true vertical face. Your idea Phil is brilliantly simple and so much easire than trying to keep pins and end frame true. Next mortar job I get will give this a go.
Thanks also for nudging me back from my slumbers - with the all business forums I felt it better to keep quiet!