lime mortar for red sandstone house front

[foxyuk]

i have just purchased a house which im renovating to live in..... the pointing is poor as sand and cement has been used to patch up previous lime mortar,,,, im getting water penetration in certain area due to the heavy rain and where my house sits.

I contacted a stonemason from yellow pages he carried out a sample however after 2 weeks its still not dry i scored it all out with my house key so obviously his samle was not up to much. additionally it has stained the bricks below..... how do i get rid of the lim mortar from the sandstone .. ive tried water, soap someone said lime...

is there cement in lime mortar?
how do i get the lime mortar off the stonefront thats run


help appreciated??

 

[bobby spray]

lime mortar takes ages to harden. there was probably nothing wrong with the mix. mine took a couple of months to fully set.

no cement in lime mortar.

 

[ABCwarrior]

Do you know if the lime was NHL(Natural Hydraulic Lime)5 or (please don't say yes!) a NON Hydraulic Lime- commonly known as putty/slaked lime?

For where you are located and the heavy annual rainfall and presumably exposed location you should be using maybe a 2 1/2 to 3 parts sand to 1 part NHL5 Lime mortar for your mix. Is it the Locharbriggs red sandstone prevalent in much of Glasgow? If so try and find a sand/gravel quarry that can provide a reddish sand it will tone down any new pointing works significantly, white and red looks baaaaad!
I take it the area he tested isn't saturated and was adequately covered for rain/wind/frost protection until the mortar adequately set(carbonated).
If it was putty lime this is a dead loss at this time of year and anyway it's only suitable for internal works (This type of lime needs the H20 out and the CO2 back in to "go off").
Even saying that the NHL5 lime should only be used between 5c-30c, if it's below that it will fail, and it needs meticulous protection for weeks.

From what you say it sounds like it's not been covered properly, or water is somehow still running over/through it and what has happened is that the lime has leached out, run down the face, entered the pores(matrix) of the sandstone and being an exceptionally thin layer has carbonated on the surface. This, I'm afraid is a nightmare to remove. Usually mechanical means either abrasives or as a last resort we've used our scablers(masons tungsten chisels) to remove the first few mm off of the face.
Ask your mason if he/she's done the NPA level 6 in Masonry Conservation(they run it at the GCBP). And don't be tempted to resort to cement for the works, it's lethal for sandstone it accelerates erosion and forms water traps.
Hope that helps?!