White fungus

Its not a fungus. Its efflorescence. Google it.

Inside or outside wall? Earth on one side? New or old bricks?

I doubt if repointing will make any difference, just remove it with a wire brush every time it gets annoying.

A wire brush can easily mark the brickwork. Diluted brick acid will dissolve it, but you don't want to do this too often as it will also damage the mortar eventually. Brick acid must be well rinsed off afterwards, and also beware of any fancy surface along the base of the wall in case it is damaged by the brick acid.

Even rain will eventually dissolve it, but only very slowly.

or pressure wash it a few times

Thanks for replies and I should have said it's an outside wall around a patio laid with Indian sandstone? so didn't fancy the idea of spraying acid around. I have a small pressure washer so I'll use that every couple of months or so and see how we go. At least your advice saved me the wasting my time and trouble repointing..

Thanks

Jb>

Well its all the strands of the growth that go in deep into the structure. Not sure its going to be an easy fix. The thing must be using something there to feed on. Brian

A neighbour recently had their roof re-slated, and the ridge tiles were mortared into place. Within a couple of weeks, the roof looked very unsightly, with white deposits streaking down from the ridge. Six months later they had all dissolved away. I remember many years ago my school chemistry master saying that mortar efflorescence was a sign of good quality cement.