Pure Pro Advice

Both methods remove dirt and organic growth, but they work in quite different ways — and not every surface is suitable for high-pressure cleaning.

What looks like simple dirt is often a mixture of algae, moss and other organic growth. Here is what causes it and why it tends to come back.

Pressure washing is extremely useful, but more pressure doesn't automatically mean better cleaning. Used incorrectly, it can damage perfectly sound surfaces.

If your driveway looks clean after washing but turns green again a few months later, you're not alone. Moisture and shade play a big part.

Render staining isn't always green. Green, black, red, pink and brown discolouration can all occur, and different types of staining can have different causes.

There isn't a single answer. It depends on the property, the surrounding trees and how much debris reaches the roof.

Decking can quickly develop green staining when exposed to moisture and shade. Timber is also softer than most hard surfaces, so it needs a gentler approach.

Moss on a roof is often treated as purely cosmetic. A little moss isn't a sign of failure, but heavy growth is worth paying attention to.

It's easy to assume exterior cleaning is just pointing a powerful pressure washer at the dirt. In reality, the machine is only one part of the job.

Many companies offer similar services, and it isn't always obvious what separates a good job from a poor one. Price matters, but so do several other things.