What is the best way to clean this exterior brick wall?

[Else]

This section of brick wall that doesn't get much direct sunlight. There's also been a fair bit of moisture underneath the building (now addressed) & some of the grouting needs repair. 

What is the best way to clean the brick, without damaging the grouting & what is the likely cause of the discolouration?  

[Else]

This section of brick wall that doesn't get much direct sunlight. There's also been a fair bit of moisture underneath the building (now addressed) & some of the grouting needs repair. 

What is the best way to clean the brick, without damaging the grouting & what is the likely cause of the discolouration?  

[JacobZ]

Hi @Else,

I'd say it is moisture-related, possibly algal growth that has occurred because the lack of sunlight doesn't dry the bricks out quickly when they become wet. It doesn't look like anything to worry about too much.

If there was no issues with the grout, then I would suggest using a pressure cleaner, however as this is a factor, I'd suggest you use a brick cleaner like this Chemtech Brick Tile And Paver Cleaner and give the wall a good scrub with a scrubbing brush like this Oates Long Handle Deck Scrub Brush or this Sabco Bamboo All Purpose Heavy Duty Scrub.

After cleaning, flush the wall with clean water to remove any remaining grime or residual cleaner.

Let me know what you think, and if you have further questions, please don't hesitate to ask.

Jacob

[Else]

Thanks Jacob : ) 

What happens to the brick & mortar over time, when algal growth isn't removed? 

And if I'm pressing cleaning an area of brick where the grout is ok, what PSI & brush type are best? 

[JacobZ]

Hi @Else,

Algae won't directly damage the brick or mortar, but it will hold moisture against the wall surface, keeping the brick and joints damp for extended periods. Because brick and mortar are porous, this moisture is drawn into the wall rather than evaporating, especially in shaded areas. Constant moisture will degrade mortar over time and brick over a much longer time. 

I don't think you need to worry too much about the algae; it is not going to cause problems if it is cleaned off regularly, but it is an indicator that moisture is present, so you should keep an eye on this area if you have had issues with moisture.

For pressure cleaning brick walls like this, it's not so much about the pressure and more about how far you hold the wand from the wall. A standard home pressure cleaner between 1000-2000 PSI will be fine as long as you hold it back from the wall around 300-400mm and use a wide, brush style spray setting as opposed to a focused jet.

Let me know what you think and if you have further questions, please don't hesitate to ask.

Jacob

[Else]

Thanks Jacob. Again, that's really helpful : )