I'm about to start on some stone walling in my garden. I read an article which said that mortar used with stone should use lime in order to ensure that subsequent (inevitable) movement is absorbed by the mortar rather than the stone. The arguement being that stone is less strong than brick/block (?) and you don't want the stone to break when the movement occurs, i.e. the mortar needs to be the weakest link! The stone I am using is a grit stone. The walls will be less than 1m tall and will be retaining flower beds. As I need to blend in with other existing walls that are constructed dry it has been suggested that I mortar the rear half or third of the stone and cover the whole of the back, like a rough render I suppose, to hold them all together. As this is my first go at "bricklaying" do we have any other opinions out there from experts? What mix would you recommend? If I used lime would I also add a plasticiser/waterproofer/frostproofer?
I use 1 cement : 1 hydrated lime : 5 sand for limestone and gritstone, and 1 cement : 1 hydrated lime : 6 sand for sandstone. The lime is a plasticiser so you don't need to add any. If it's cold use a frost proofer like Feb Wintamix and cover your work with hessian. I use exactly the method you propose for facing retaining walls with stone and making them look like dry stone walls. Also you have the advantage that there is no pointing and you can build in damp conditions without the risk of mortar smearing the face of the stone. Retaining walls should be a minimum of quarter of the height thick at the base (unless reinforced).
Thanks Limestone, nice to hear it confirmed independantly, just hope it warms up a bit for the weekend now!
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