Exterior white plaster algae

Hi,
We have white coloured render on the exterior of our house for 9yrs. In recent months we have noticed pink ish colour coming thro on the chimney stack mostly on the side receiving less sunlight..possibly an algae of some discription. Any idea what causes this and possible treatments to reduce it?

It is a fungal growth. There are plenty of companies out there how will treat it. however, it you tackle it before it spreads to far you can treat it yourself.

Bleach will kill it. I normally buy 5l of sodium hypochlorite. put it in a small garden sprayer and dilute according to the instructions. Pick a day with no wind and wear old clothes along with protective gloves, googles and mask.

For a light growth, the results can be seen in a few minutes.

Thank you Gareth1214, great advice. Very high chimney so will prob have to get a cherrypicker or scaffoldling, or alternatively someone who is used to working on heights. Algae only on one side of the chimney at the moment, but I can see it sneaking around the corners so prob better to nip the algae in the bud. Thank you for suggestion & great health/safety recommendations also.

I did nt know where to purchase sodium hypochlorite in the end so I used a fleetwood fungicidal wash and it has worked brilliantly.A guy fitting a chimney cowl came to my assistance with the application.