Once cleaning strips away the grime that was disguising it, failed pointing on a patio becomes obvious — crumbling mortar, gaps between flags, sand washing out in the rain. The question that follows is whether to patch the failed sections or re-joint the whole patio from scratch, and the answer depends heavily on how widespread the failure actually is.
It's worth resisting the instinct to assume the worst just because the visible joints look bad — cleaning often makes existing joint problems more visible than they were before, without meaning they've all failed equally.
When targeted pointing repair is the sensible route
- Failure is concentrated in specific areas — often edges, high-traffic paths or joints near downpipes and drainage.
- Most of the patio's jointing is still sound, with only isolated gaps or crumbling patches.
- You want to keep costs and disruption down while addressing the areas actually causing problems, such as weed growth or trip risk.
When full re-jointing makes more sense
- Mortar failure is spread evenly across most of the patio rather than isolated in a few spots.
- The original jointing material was poorly mixed or applied and is failing prematurely across the board.
- You're planning other work on the patio at the same time and want a consistent finish throughout rather than a patchwork of old and new pointing.
Why matching old and new mortar matters
Patch repairs sit right next to decades-old original pointing, so colour and texture matching matters more here than in a full re-joint, where everything is new and consistent together. A repair that stands out as an obvious grey patch against aged mortar undoes some of the benefit of doing the work at all.
What cleaning has to do with the decision
A wash and biocide treatment doesn't cause joint failure, but it removes the dirt and moss that were physically holding failing mortar together, which is exactly why pointing problems often only become visible once a patio has been properly cleaned. That's a useful moment to assess jointing honestly rather than a sign anything's gone wrong.