I was walking around yesterday waiting for my car to be fixed and being in the ‘trade’ it just struck me how many stone walls in Cardiff have been re-pointed using cement. Almost every house (that wasn’t covered in cement render – don’t get me started!!) had cement in a similar condition to the photo. The hard cement has been placed over the old lime mortar and is now just falling away, looking awful, whilst still managing to increase the moisture content in the wall.
The whole process is ruinous in a number of ways:
1. Most importantly the mortar used should be a lime based mortar (ideally with a stone dust aggregate), the cement used just helps to trap moisture in the wall and this leads to a host a other damp problems internally
2. Any re-pointing should involve the removal of the old mortar. Just placing mortar over the top means that any loose mortar underneath just weakens the whole repair. It also means that that mortar doesn’t bind to the stone / brick properly, it then just falls off looking cheap and like you just don’t care about your property
3. The mortar here has been placed so that it juts out where it should be level to the stones / bricks. If it is protruding it is more likely to ‘catch’ rainwater and bring it into the walls again giving yourself damp problems
So, when you are paying a lot of money to have a whole wall re-pointed (most of the cost is in labour and scaffolding), why not get the materials right and save yourself the cost of a) having to have it done again within a couple of years, and b) having to deal with the subsequent damp that it is likely to attract into the house.