Re-Pointing : How much to charge?

You need to do a proper job to protect yourself from appearing in a post here, as one of the bad guys, one day!!!! Check out your local Further Ed college, they may have a short course on repointing as its a more complex issue than a one-size fits all answer. It depends on what the previous pointing was done with, and its condition, the age, and type, of the house etc. etc.

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In my opinion its not a good idea to repoint some joints and not others as you will more than likely end up with different colour mortars . Pointing to a high standard is not as simple as it may seem ,if you have not had any past experience repointing, i would suggest that all joints are raked out and you use one of the epoxy based mortars which are available in most builders merchants and diy stores .This product is simple to use as it is vacuum packed ,simply cut the bag open turn the mortar over with a trowel and brush into the joints and its available in different colours and wont stain the slabs .The materials may cost more but the man hours should be at most a third .