Understanding House Washing: Removing Dirt, Stains, and Pollutants

house washing by pro waterblasting

Estimated reading time: 8 minutes

Maintaining the appearance and longevity of a house should be a priority for homeowners. Unfortunately, the cleanliness of house’s exterior surfaces often goes unnoticed. Over time, dirt, stains, and pollutants accumulate on all surfaces, leading to unsightly appearances and potential damage. This is where regular house washing plays a crucial role.

The impact of dirt, stains, and pollutants on home surfaces are vast. They not only detract from the visual appeal of a home but can also cause long-term damage and premature degradation. Exterior surfaces, such as weather boards, brick, and wood, are constantly exposed to the elements, making them vulnerable to dirt buildup, mould growth, oxidation, algae, rust, and other unsightly stains. By investing in a professional house washing service of Pro Waterblasting or adopting do-it-yourself cleaning practices, homeowners in New Zealand can maintain the cleanliness and attractiveness of their homes. 

How Dirt Adheres to Surfaces

Dirt particles may seem insignificant, but the compounding effect of their buildup lays the building blocks for other types of mould to take hold and eventually cause the premature breakdown of the surface. Understanding this process helps show why dirt accumulation occurs and why it can be challenging to remove.

The structure of dirt particles varies depending on their source and composition. Common dirt particles include dust, pollen, soil, soot, and other organic and inorganic matter. These particles are often tiny and can range from a few microns to larger particles visible to the naked eye.

Here are some of the factors that result in dirt accumulation – 

  • Static electricity – static charge attracts and holds onto dirt particles like a magnet, making them adhere to the surface
  • Moisture – When surfaces become damp or wet, dirt particles can mix with the moisture, forming a paste-like substance
  • Environmental factors –  Wind, for example, can carry dust and debris, depositing them onto various surfaces. This is particularly noticeable in urban environments; pollen, plant matter, and agricultural dust may be more prevalent in rural areas.

The combination of static electricity, moisture, and environmental factors creates an environment conducive to dirt accumulation. Over time, as dirt particles continue to adhere to surfaces, their presence becomes more visible and challenging to remove.

Types of Stains and Their Adhesion Mechanisms

Stains can significantly impact the appearance of surfaces, and understanding the mechanisms by which they adhere can help effectively remove them. Let’s explore some common stains and the specific adhesion mechanisms associated with each:

  • Mould and Mildew: Mould and mildew are common stains that thrive in moist environments. They are typically caused by fungal spores that land on surfaces and find favourable conditions for growth. These spores attach to the surface using tiny structures called hyphae, which penetrate the material. As they multiply, they produce enzymes that break down organic matter, further anchoring them to the surface. Moisture and organic materials sustain mould and mildew, allowing them to persist and spread.
  • Algae: Algae stains are another organic growth commonly found on outdoor surfaces. Algae spores are dispersed through the air or carried by water and can settle on surfaces. They adhere using structures like rhizoids or holdfasts, which anchor them to the material. Algae stains often appear as green or brown patches and can be challenging to remove due to their tenacious adhesion.
  • Rust: Rust stains occur when metals, such as iron or steel, oxidise due to exposure to moisture and oxygen. Oxidation causes a chemical reaction that forms iron oxide, commonly known as rust. The rust particles bond with the material through iron bonding, making them easier to remove with appropriate cleaning techniques and products.
  • Oil: Oil stains, including vehicle leaks or cooking spills, can be stubborn and visually unappealing. Oil adheres to surfaces through hydrocarbon bonding. The porous nature of some materials, like concrete or brick, can absorb oil, making it more challenging to remove without specialised cleaning agents.

Each stain type has unique adhesion mechanisms, making it essential to employ specific cleaning methods tailored to the stain. Understanding these mechanisms helps select the appropriate cleaning agents and techniques to remove the stains effectively.

When dealing with stains, it is crucial to consider the surface and the underlying cause. Identifying and addressing the source of the stain, such as a leak or excess moisture, is essential to prevent future occurrences.

Professional house washing services like Pro Waterblasting often employ specialised cleaning solutions and techniques to effectively target and remove specific stains. By understanding the adhesion mechanisms of different stains, homeowners and professionals can choose the most appropriate methods for achieving a clean and stain-free surface.

Additional Read: How to Clean Your Wooden Deck [Step-By-Step Guide]

Understanding Pollutant Build up

Understanding how pollutants accumulate on exterior surfaces is crucial in recognising the need for regular house washing and maintaining a clean environment. Pollutants, ranging from air pollution to pollen and bird droppings, can accumulate on exterior surfaces due to various factors:

  • Air Pollution: Air pollution significantly contributes to the build-up of contaminants on exterior surfaces. Gases and particles released from industrial emissions, vehicle exhaust, and combustion processes can become suspended in the air. Air currents carry these pollutants and settle onto surfaces, including the exterior of buildings. Over time, accumulating these pollutants results in a visible layer of grime and discolouration.
  • Pollen: Pollen, a fine powder produced by plants, is another common outdoor pollutant. It is released during the reproductive process of plants and can become airborne. The accumulation of pollen can create an unsightly appearance and trigger allergies in sensitive individuals.
  • Bird Droppings: Bird droppings contain a mixture of waste products, including uric acid, undigested food, and water. Bird droppings not only detract from the aesthetic appeal of a property but can also damage surfaces over time. The acidity of bird droppings can lead to corrosion, staining, and degradation of materials such as paint, metal, and wood.
  • Environmental Dust: Environmental dust can come from construction sites, nearby roadways, or natural sources such as deserts or agricultural fields. The accumulation of dust can create a layer of grime and contribute to the deterioration of surfaces.


Cleaning Methods and Their Effectiveness

Cleaning methods are crucial in removing dirt, stains, and pollutants from exterior surfaces. Let’s explore some common house washing methods, including water blasting, soft washing, and eco-friendly alternatives, and understand how they work to target specific contaminants:

  • Water Blasting: water blasting utilises high-pressure water jets to dislodge and remove stubborn dirt, stains, and pollutants from surfaces. The principle behind water blasting is the forceful impact of the water, which helps break the adhesion between the contaminants and the surface. The high-pressure water effectively removes grime, mould, mildew, algae, and even tougher stains like oil or rust. Water blasting suits robust materials like concrete, brick, and metal. However, caution should be exercised on more delicate surfaces to prevent damage.
  • Soft Washing: Soft washing is a gentler alternative to water blasting, using low-pressure water combined with specialised cleaning solutions. The cleaning solutions are designed to effectively kill and remove algae, mould, mildew, and other organic contaminants. The low-pressure water application ensures that delicate surfaces, such as siding, stucco, or wood, are not damaged. Soft washing is particularly effective in removing stains caused by biological growth without the risk of surface erosion or damage.
  • Eco-Friendly Alternatives: Eco-friendly house washing methods focus on minimising environmental impact while effectively cleaning exterior surfaces. These alternatives often involve using biodegradable cleaning solutions that are safe for plants, animals, and water sources. 

It’s important to note that different surfaces and situations may require different cleaning methods. By selecting the right cleaning method, homeowners can achieve optimal results in removing dirt, stains, and pollutants while maintaining the integrity and longevity of their exterior surfaces.

Safety Considerations

While DIY house washing can be done safely, there are advantages to hiring professionals like Pro Waterblasting for this task:

  • Expertise and Experience: Professional house washing companies have the knowledge, experience, and equipment to handle various surfaces and stains effectively. They are trained in proper cleaning techniques and can ensure thorough cleaning without causing damage.
  • Time and Efficiency: Professionals can complete the job efficiently, saving time and effort. They have access to commercial-grade equipment, allowing them to clean larger areas more quickly and effectively.
  • Safety and Insurance: Professional house washing companies prioritise safety and carry liability insurance. They are well-versed in handling equipment, using appropriate cleaning agents, and adhering to safety protocols to minimise risks.
  • Customised Approach: Professionals can tailor their cleaning methods and solutions to specific surfaces and stains, ensuring optimal results without compromising the integrity of the materials.

Hiring Pro Waterblasting for house washing ensures a thorough and safe cleaning process and provides peace of mind knowing that your property is in capable hands.


Maintaining a clean and well-maintained home involves understanding the science behind house washing and choosing appropriate cleaning methods. While DIY house washing can be done safely with proper precautions, hiring Pro Waterblasting for house washing services, offer numerous benefits, including expertise, efficiency, safety, and a customised approach. By entrusting your house washing needs to professionals, you can enjoy optimal results, extend the lifespan of your home’s surfaces, and ensure a clean and visually appealing property for years.