the old stone firms mix which i was taught in the early 1970s was 7 parts stone dust /sand 5parts hydrated lime 2 parts white cement.use to be like spreading butter.
Use PHL 3.5 lime with 3 sand for historic buildings. PHL will set. Not NHL. Lime mortar is vapor permeable. Cement based mortar is not and will cause efflorescence in the stone/brick. PHL (pozzolain hydraulic lime [used by Romans for 2,000 years]) will set just like Portland cement mortar. In addition, this guy has the thermal issues resolved but NOT the vapor permeability. His 7-2-2-1 cement based mortar will expand and contract with the old stone, but will force water through the stone causing a leaching of minerals to the surface (efflorescence).
What mix would you use for ridge tiles fixing and pointing on a front door porch? Is that mix strong enough to stop them flying off in a British gale??
I got an old farm limestone/sand stone out building thats is crumbling in the lower two or three layers of stone. I need to strengthen the wall not make it look pretty. What mix should i use? I live in hot dry climate. I dont know if that makes any difference
It's not a bad mix though. 9 sand is being very generous and sensible. It's been found that buildings with sand ratios of between 9 and 13 sand to 1 cement have done really well. The addition of the lime hydrate will mainly act as a plasticiser and there's no difference between white and grey cement but... at least it's not a 1:1:4 or 5 mix.
