Caring for Purbeck Stone: A Property Owner's Guide

Two Methods, Very Different Results

When people talk about exterior property cleaning, pressure washing is often used as a catch-all term. But there are actually two distinct methods — soft washing and pressure washing — and choosing the wrong one for your surface can cause serious, costly damage.

At PowerWash Bros, based in Swanage, we use both methods — but we are very deliberate about which we apply to each surface. Here is everything you need to know.

What is Pressure Washing?

Pressure washing (also called jet washing) uses high-pressure water to physically blast dirt, moss, algae, and staining from surfaces. The mechanical force of the water does the cleaning work.

Best Suited For

• Concrete driveways and paths
• Block paving
• Tarmac surfaces
• Hard stone patios
• Certain commercial surfaces

Key Characteristics

• Fast and visually dramatic results
• Works well on robust, hard surfaces
• Can strip away organic growth quickly
• Does not kill organic growth at the root — regrowth returns within months without biocide treatment

What is Soft Washing?

Soft washing uses low pressure combined with specialist cleaning solutions — typically biodegradable biocides — to clean and sanitise surfaces. The chemistry does the work, not the water pressure.

Best Suited For

• Roof tiles (all types, including Purbeck stone)
• Rendered walls and painted surfaces
• UPVC fascias, soffits, and gutters
• Timber cladding and decking
• Older and more delicate surfaces

Key Characteristics

• Safe for delicate and porous surfaces
• Biocide treatment kills organic growth at the cellular level
• Results last significantly longer — often 2–3 years before retreatment is needed
• No risk of damage from excessive water pressure

Why the Distinction Matters for Purbeck Properties

Purbeck has a high proportion of older and traditional properties — stone buildings, lime-mortared walls, heritage tiles, and rendered cottages. Many of these surfaces simply cannot withstand high-pressure washing.

Using the wrong method causes real damage:

• High pressure on render can crack and detach it from walls
• Pressure washing Purbeck stone can erode the surface and strip protective patina
• Jet washing roof tiles can dislodge them and damage pointing
• High pressure on timber can raise the grain and cause premature deterioration

We see the aftermath of DIY jet washing mistakes regularly across Purbeck — and the repairs are always more expensive than proper cleaning would have been.

Our PowerUps Approach

At PowerWash Bros we use our proprietary PowerUps Bio-Clean system across all soft wash applications. This combines BAC50 biocide (effective against moss, algae, lichen, and mildew), purpose-formulated surfactants for cleaning without abrasion, and low-pressure application equipment that protects all surface types.

For hard surface cleaning we use calibrated pressure washing at the correct PSI for each surface type, combined with biocide post-treatment to extend the life of results.

Quick Reference: Which Method for Which Surface?

• Roof tiles — Soft wash only
• Rendered walls — Soft wash only
• UPVC and fascias — Soft wash only
• Purbeck stone — Soft wash only
• Concrete driveways — Pressure wash + biocide
• Block paving — Pressure wash + biocide + re-sanding
• Patios — Pressure wash or soft wash depending on material
• Timber decking — Soft wash preferred

Get the Right Treatment for Your Property

If you are unsure which method is right for your surfaces, we offer free, no-obligation assessments across Purbeck and Dorset. We will inspect your property, tell you exactly what is needed, and provide a clear, honest quote. Get in touch via WhatsApp — we are based in Swanage and cover all of Purbeck and beyond.