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Mould/mildew on Exterior Paint

Hi, just after some advice on best way to deal with mould growing on this exterior paint.

I’d usually use Dulux Multisurface Fungicidal Wash, apply it and leave for 24 hours, then wash off and apply paint. But having read up a bit on the internet I’m now wondering if I need to take off the paint from affected areas completely?

I guess I’d need to find out if the paint is just growing on the mould or coming through it, by scraping a section off and seeing what’s underneath the paint?

If anyone has used the Dulux product, they may have noticed that it doesn’t actually get the stuff off, but just kills it (one hopes). This will sound a stupid question, but is it strictly necessary to scrub scrub scrub a surface like this until there’s nothing left?

Any advice gratefully received.

Anyone want to put me straight? I do honestly love free advice!

Hi David,

Looking at your picture thats not mould its Algae formation from the plants around the trellis work. Try washing down with some diluted household bleach (careful of the plants) then use a pliolite based masonry paint as opposed to a water based one. Thin the first coat by 15/20% and spot primed effected areas followed by two full coats.


Hi Russ,

Firstly, thanks for your reply and apologies for the extreme tardiness of mine.

I will take your advice re: a bleach washdown, but I’ve not heard of pliolite. What is it, and how would it help on this job? I’ve googled it, there isn’t much info available and I think only Glidden make one. I’m interested, though.


Hi David,

Sound advice from Russ, I like to pressure wash off the bleach after 24hrs as it helps to see if it needs another application. But after washing off, the masonry will need to dry out for at least another day (maybe more depending on weather conditions).

Pliolite is an oil based masonry paint most manufacturers supply one, Johnstone, Crown, Dulux, Leyland, Sandtex etc but it might be labelled up as All Seasons, 365 All Weather, your local merchants should be able to tell you what they stock.

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Ah, if Dulux sell it as “All Seasons” that would explain why they don’t sell a Pliolite paint.

Is Pliolite just better all round as exterior paint? What brand do people tend to use?

evening david

the advice from russ and the welsh decorating decorator are i have come across this problem,which will always occur where trees,scrubs,plants are present,its a weather thing. wet,moisture ect. but i use a fungicidal wash, pressure wash off.then to be sure of no bleed through use zinseer bin as a primer.then 2/3 coats of pliolite masonry finish. the best brand in my opinon is the sandtex 365 .by the way pliolite means plasticised/resin- a dry acrylic copolymer binder…i would wait till the weather changes for best results april/may or if yuou cant wait use the oil based alternative…but you will have to throw away your roller,brushes after use.or spend days cleaning them out…mick MPD DECORATING

Hi David,

You obviously tried the fungicidal wash, that’s why I suggested bleach, it works great for this type of work and its cheap! Always rember to neutralise by washing down again after applying bleach.

I know mick mentioned priming with ZinBIN but with respect to him, I would be wary to use ZinBIN as an external primer (Spot priming only!) as its shellac based it can become quite brittle if applied to large areas. I personally would stick with the Pliolite masonry and 3 coats should more than suffice. Just make sure the substrate is completely dried out prior to application.

Dulux All Seasons, Johnstones or Sandtex would be my top 3 choices for that particular project!



hi russ

i have also used zinsser perma white water based to prevent further growth of mildrew as a primer under 2/3 coats of sandtex pliolite. regards mick


Zinsser Perma White is a great product in its own right for extending maintenance cycles for problamatic areas but again would not recommend as a primer for this type of application!

Perma White contains active mildewcides including Zinc Oxide, these prevent the spores from mildew and mould from reattaching themselves to the substrate. By over coating this product with other products, defeats the intention of what the product is originally designed for as the mould spores will reattach themselves to the over coated product.

Zinsser Perma White (Exterior) and Zinsser Watertite would be a good alternative spec for this substrate but not as a primer! Use them on their own!

I found a brilliant product to eliminate mould & alge its Dairy Farm Hypochlorite. dilute 50/50 with water spray on let it sit for 1 hour % rinse off. use it in your shower & on tiles it is fantastic

This is it. Not used it, how far do you dilute?

Hi I am starting a exterior off a park home on a riverside location,i have jet washed ,and used a fungerside,just on the front it has taken two attempts, using large brush ,was thinking off using bleach? As for the fungerside ordered five litres, thought what might help is to put it into a pressure spray at the moment just using small bottles with such a large area to cover.My question what’s the most effective fungerside on the market, any tips on anything that will help much appracited.