Exterior prep

[Dee]

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

[nod]

Wash down with Alga-cide 

[Dee]

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

[Redbeard]

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

What does it do?

 

 

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

[Dee]

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

[G and J]

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

[Redbeard]

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.

[Dee]

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

[ProDave]

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.