Hi all
I'm repointing a friends property in a couple of weeks, a 1960's semi detached bungalow, and this will be my 2nd time doing it, the first time was whilst I was an apprentice bricklayer a couple years back.... (I didn't finish the training so I am not a bricklayer currently!) so this is my first repointing job on my own. I have all the equipment, dust extraction, grinder with raking blade and raker bit etc. The mortar is failing as it's crumbling away. Looks like someone has not too long ago, repointed the back of the property and one side of it, in a bucket joint finish. It's not the neatest work and looks pretty rushed, I'm not convinced they have even raked out the crumbling existing mortar and just pointed sand and cement on top... however the areas that haven't been repointed need sorting. It is crumbling away with various holes and looks recessed as the top layer has just gone. So I took a sample and it fizzed away in white vinegar suggesting lime is present. I also added a sample into some water, shook it up and let it settle to see the different layers to establish ingredients that may have been used.
My initial thoughts were to do a mix of 6:1:1 - Sand, Hydrated Lime, Cement. I came across this after some basic research from someone online who said that would have been the likely mix back in the 1960's.
Given its a cavity walled property, I know it's not going to be Hydraulic Lime NHL 3.5. However, there seems to be some slightly more course aggregate in the mix upon visual inspection and the sample mixed in the water suggests that perhaps?
I have attached some photos to assist and would really appreciate someone's experienced suggestions on the correct mix. I would like to use hydrated lime if it was present before to be in keeping with what is there and to even assist somewhat in a colour match. What type of sand should I use?
Thanks everyone!
Image 1 - Existing mortar looking pretty recessed and failing!
Image 2 - Fizzing mortar in vinegar