Why Is Regular Washing of Flat Roofs on Apartment Buildings Important?

Flat roofs are most commonly seen protecting apartment buildings. However, due to their shape, the surface tends to get dirty frequently. To keep the roof functional and avoid the need for repairs after just a few years, it is important to focus on regular washing and cleaning. This will extend its lifespan and also prevent water ingress and other complications.

How do you know when your roof needs washing, and why does it matter so much? The roof is certainly one of the most important forms of protection for the entire building. As soon as it is damaged in any way, the occupants feel it immediately. A simple trick for extending the lifespan of flat roofs is regular cleaning, which removes not only accumulated dirt but also moss, algae and lichen. In this article, we will walk you through everything you need to know about washing flat roofs.

What happens when you leave your roof uncleaned for a long time?

Just as with a facade, dirt and accumulated microorganisms are a problem not only aesthetically but above all functionally. Layers of dirt and deposits can significantly affect how well your roof performs. So what can happen if the roof does not receive the care it needs?

1. Accumulation of dirt and organic material — leaves, branches, dust and moss can gradually block drainage systems, leading to water pooling and ingress.
2. Growth of microorganisms and moss — mould and algae take hold in joints and damage the protective surface of the roof membrane.
3. Deterioration of thermal insulation properties — dirt affects the roof's ability to reflect heat, causing temperatures inside the building to rise (especially in summer).
4. Shortened waterproofing lifespan — dirt and biological deposits increase the risk of cracking, material degradation and subsequent water ingress.

Roofs and all the repairs associated with them are certainly not cheap. Prevention is always better than dealing with the damage afterwards.

How often does a roof need to be cleaned?

Every building, facade and roof is slightly different and is affected by different factors. Buildings in cities, near trees or busy streets will need washing more frequently.

The frequency of washing will also depend on the roofing material and the overall condition and age of the roof. As a general rule, however, it is recommended to wash the roof at least once every three years. Manufacturers of insulating roof membranes recommend washing roofs every three to eight years.

The flat roof washing process

Washing flat roofs on apartment buildings should always be carried out by a professional company. When choosing one, focus on the company's equipment and experience, as particular care is needed when it comes to roofs and washing roof coverings.

The standard washing procedure includes:

1. Removal of coarse debris — leaves, branches, plastic packaging.
2. Cleaning of drainage systems — downpipes, drains, gutters.
3. Application of cleaning agent — suitable for the roof type, usually gentle on waterproofing layers.
4. Pressure washing — using professional equipment that does not damage the surface.
5. Surface inspection — minor repairs, identification of cracks or suspected water leaks.

Who should carry out the washing?

As mentioned above, washing should be carried out by a professional company with experience. At Umyjem To, we wash roofs using high-pressure cleaners, ensuring that the roof is thoroughly yet gently washed.

An unprofessional intervention can damage your roof and end up costing you more than having it washed by an experienced company.

Benefits of regular cleaning

Prevention is the foundation, and regular washing — of both roofs and facades — can extend their lifespan and save you a great deal of money.

• Extending the roof's lifespan by several years
• Preventing costly repairs and water ingress
• Reducing the risk of mould developing in apartments
• Maintaining the building's aesthetic appearance
• Lower interior cooling costs in summer

Flat roof washing is often overlooked because it is not as visible as a dirty facade — yet it is extremely important for maintaining the roof's functionality and lifespan. Investing in regular maintenance pays off — it protects the property, the health of the occupants, and the HOA's budget.

Frequently asked questions

How do you clean moss off a roof?

First remove any larger debris from the roof, then apply a chemical moss treatment.

How long does a flat roof last?

A flat roof typically lasts 20–30 years, depending on the material and maintenance.

How do you get rid of lichen on a roof?

Use a specialist lichen removal product, leave it to work, then rinse off with water.