Mechanical Cleaning vs. High Water Pressure: Why Brick's Original Coating Requires Gentle Treatment

A tile roof is one of the most popular roofing materials in Finland, and for good reason: it is long-lasting, quiet, and looks valuable. For the tiles to retain their properties for decades, they require regular maintenance. One of the most common questions regarding maintenance is whether the roof should be washed with high pressure or cleaned mechanically. While pressure washing may seem like a quick and effective solution, it hides risks that can be fatal for the tiles.

In Finland, weather conditions place high demands on roofs and facades. Temperature fluctuations, snow, ice, and constant moisture stress the materials. In this article, we delve into why the original coating of brick is such a critical factor for the health of a building and why experts favor gentler methods, such as mechanical cleaning.

The fired surface of a brick is its most important protective layer

The brick manufacturing process is an invention thousands of years old, refined with modern technology. When clay is shaped into a brick and fired at high temperatures, a dense and hard layer forms on its surface. This is called the fired surface. It is the brick's primary line of defense against external stresses. The fired surface is not just an aesthetic feature, but a functional part of the brick: it prevents water absorption into the brick and protects it from the sun's UV radiation and air pollutants.

When a brick is new, it's smooth and naturally repels dirt and growth. Over the years, however, dust settling from the air and tree leaves provide a growing medium for moss and lichen. It's at this stage that many property owners make the mistake of choosing too harsh a cleaning method. If the burnt surface is damaged, the brick's porous structure is exposed. This makes the brick like a sponge, absorbing water with every rainfall.

Professional Roof tile maintenance is always based on preserving this original protective layer. If the surface has already become worn, it can be re-protected in certain cases, but the best result is always achieved with proactive and proper cleaning that does not unnecessarily wear down the surface.

Damage to a brick structure caused by high water pressure

Many consider a pressure washer the best tool for removing dirt, but the situation is different when it comes to brick. High-pressure washing, where water is sprayed at hundreds of bar pressure, is comparable to sandblasting. The water jet not only removes moss but also tears away pieces of the brick's surface. This phenomenon is often invisible to the naked eye immediately after washing, but the damage becomes apparent within a few years.

When water pressure is too high, it opens the microscopic pores within the bricks. As the pores open, they provide moss roots – that is, mycelium – with an even better grip. It is therefore common to notice that a pressure-washed roof re-mosses considerably faster and more vigorously than before. Furthermore, water can be forced with high pressure through the gaps between the bricks into the substructure, creating an immediate risk of moisture damage in the roof space.

Especially older bricks, which are already naturally somewhat weathered, cannot withstand heavy mechanical stress. Pressure washing can also damage the laps and joints of the bricks, weakening the roof's seal. Therefore, we always recommend considering alternatives where cleaning is done in a controlled manner and without force that would damage the brick surface.

Mechanical cleaning advantages compared to pressure washing

Mechanical cleaning means removing vegetation by hand or with specialized tools designed for the purpose, such as brushes and scrapers. This method is significantly gentler than pressure washing. When Moss removal it is performed mechanically, the worker can regulate the force used and consider the condition of the brick individually.

The key benefits of mechanical cleaning are:

• Surface retention: The firing surface of the brick remains intact, which keeps the water repellency of the brick as good as possible.
• Longer service interval Because the brick surface does not roughen, moss has worse conditions to reattach to it.
• Structural safety: No large amounts of water are used under pressure during cleaning, so the risk of water entering the insulation is negligible.
• Targeted work A professional sees the condition of each brick during cleaning and can report any broken bricks that need replacement.

After mechanical cleaning, the roof can be treated with an anti-moss agent, which destroys any remaining spores and root systems deep within the pores without needing to scrub the surface. This combination has been scientifically proven to be the most effective way to keep a tile roof clean and functional for a long time. At the same time, it makes sense to ensure that the rainwater system is in good order so that material washed off the roof does not clog the gutters.

How does excessive moisture strain damaged brick

If the surface of a brick has been damaged due to rough handling or neglect, moisture is its greatest enemy. Porous bricks absorb water like a sponge. In a Finnish winter, this is a critical problem. When the temperature drops below freezing, the water inside the brick freezes. As it freezes, the water expands by about 9 %, creating enormous pressure inside the brick.

This process is called frost weathering. Repeated freeze-thaw cycles break down the brick's structure from within. Initially, small pieces may break off the brick, but over time, the entire brick can crack or crumble into dust. When a brick loses its structural integrity, it no longer protects the building from water, and the risk of expensive roof repairs increases significantly.

Moss and lichen further worsen the situation. Moss keeps the roof surface constantly moist, as it binds many times its own weight in water. If moss is not removed and the gutters are blocked, water will stand on the roof and in the gutters, which further accelerates weathering. Therefore, regular gutter cleaning is an essential part of comprehensive property maintenance that supports the health of a tiled roof.

This is how you preserve the value of a facade with gentle methods

Maintaining the value of a property is long-term work. A tile roof and tile facade are visible parts of a building, and their condition directly affects the market value of the entire property. By choosing gentle and professional maintenance methods, you ensure that the building remains presentable and technically functional for decades to come.

Action Plan for Rational Maintenance

1. Regular inspection: Check the condition of the roof and gutters at least twice a year – in spring after the snow has melted and in autumn before winter arrives.
2. Mechanical cleaning: Remove visible moss and debris in time, before they can root deeply.
3. Maintenance of roof safety products: Ensure that the ladders and snow guards are securely fastened. Safe work on the roof is only possible when the equipment is in good condition.
4. Use by expert: If you're unsure about the condition of your tiles, have a professional come by to assess the situation. A professional can tell you when a simple cleaning is enough and when more extensive protective measures are needed.

We serve broadly across Finland, including in Uusimaa, Pirkanmaa, Southwest Finland, Kanta-Häme, and the areas of Oulu, Jyväskylä, and Kokkola. We offer comprehensive services, such as gutter cleaning, tile roof maintenance, and moss removal on a turnkey basis. Our work is eligible for household deduction, making the use of a professional even more profitable.

Remember that roof maintenance is an investment, not an expense. Maintenance performed with the right methods will postpone roof renovation by years and ensure peaceful nights, whether you know there's a meter of snow above your roof or a downpour. Choose a safe and durable way to maintain your home – choose mechanical cleaning and professional service.