Stone wall topping

Nhl 5 and do 5 and 2 mix with Jews on sharp sand good big bits off aggert in it to bond together keep damping down

Firstly 3:1 is enough I take it you used sharp sand, you can use nhl5 outside and keep it damp until it goes off. I have done some test pieces outside it really doesn’t hold up well on horizontal surfaces! you can put goats hair in it to bind it, I know it defeats the object but I would consider using a small dash of white cement at a ratio of 7:1

why are you using N.H.L. and cement as one is breathable and the other is not one allows movement and the other does not, by putting N.H.L in cement it will achieve nothing other than expensive cement.

The reason it’s all cracked is because of shrinkage. As it’s only mortar with no stone pinnings through it, it has no structure, and when it’s dried it’s shrunk and cracked. It doesn’t matter what mix you’ve used as with no pinnings, it won’t stand a chance. Smash up lots of stone to the size of an egg, or tangerine if you’re a vegetarian:) These are your pinnings. Soak them in water and place them all through the structure your trying to form. ( if you use them dry they’ll draw the moisture out of your mortar and it will fail ) A minimum ratio of pinnings to mortar would be 60/40. If you look at concrete it’s full of aggregate, same reason. Keep your mortar covered and damp for a minimum of 72 hrs. One last bit of advice re which mix. I would advise either a 2:5 NHL5/Sharp Sand, or if you can get it St Astier make HL binders which are perfect for this purpose. They are predominantly NHL5 but contain 2% natural cement and a hydrophobe which helps expel water whilst retaining its breathability.