I'm contemplating painting the exterior of our house but I'm unsure of the prep needed.

The brickwork has previously been painted with a white sandtex type paint. 

Due to the texture there's alot of grime and algy (tree spores)

Do I need to treat the walls with anything before painting?

What prep do I need to do?

Thanks

Wash down with Alga-cide 

It's a very big detached house! Wash with a brush or pressure washer? What does it do?

On 21/08/2025 at 22:02, Dee said:

What does it do?

 

 

Sorry, what is the 'it' in your Q ? The algaecide?

Sorry to be brief; What is the purpose of the algaecide ? Does it prevent growth? Help paint adhere? 

If it wasn't used would repainting fail?

Thanks

Come and look at our neighbours house.....yes the paint will peel off.

Strictly it does not help the paint adhere to the building; it (and a bit of scrubbing) takes off any algae to which the paint would otherwise adhere, rather than to the brick. If you paint over the algae - algae falls off; paint falls off. After application of the algaecide you once more have propitious conditions for the paint to stick to the wall.

Ah, OK. It's a huge house to scrub@ is there a spray option or paint product that has algaecide mixed in ?

Appreciate your advice alot

When I had a pebbledashed and painted house, before re painting, I just pressure washed the whole house and let it dry before re painting. That removed all algae and any loose paint.