Effective facades cleaning – from plaster to metal

Maintaining the exterior of a building helps retain or increase its value. Various methods are available to clear dirt from facades, but the surface should be taken into consideration when applying the respective technology. This is essential for avoiding damage.

Worker pressure washes the facade of a building

The standard: Cleaning with hot water and steam

Facades are the flagships of buildings. Often they are large, complicated surfaces made of different materials. Exposed to external environmental influences for years, dirt can settle and accelerate weathering in different ways.

Hot water pressure washers have proven to be effective, economical tools for facade cleaning due to their high cleaning performance by low water consumption. Pressure washer trailers make it easier for building exterior cleaning since they allow for flexibility when an electricity or water network is not within reach.

The advantages of hot water pressure washers compared to cold water pressure washers are based on two aspects:

Unlike cold water pressure washers, workers can, besides water volume and pressure, also use the temperature factor with hot water machines. If cleaning is done in a temperature range between 140 and 175 °F, this leads to a significantly faster breakup of encrusted dirt and deposits. Oil, grease and soot can be removed more easily. The depth penetration is also higher so that roots of moss and lichens are removed, thus preventing any regrowth.

Worker uses a hot water pressure washer with EASY!Force gun

A second advantage of using hot water pressure washers is the option for steam cleaning. Through this process, water volume is reduced by half, and up to 310 °C steam is discharged. This allows for very intensive cleaning which effectively tackles stubborn dirt such as paints or bituminous coatings. The low working also pressure protects sensitive surfaces.

Steam cleaning sensitive surfaces

A preliminary test is wise:

Choose the right technology, avoid damage.

No matter which facade material you are cleaning – in order to select the correct technology, a sample area should be tested extensively beforehand. Is the facade sensitive to acids? Does it absorb water? Which cleaning detergent achieves the desired effect in which concentration and time? Those who proceed carefully in advance achieve the desired result and avoid loss of substance or other permanent damage due to the incorrect cleaning detergent.

It's all about the material: Cleaning of different facade types

Enhanced effect due to cleaning detergents

cleaning detergent can further enhance the effect of a pressure washer if required. The so-called two-step method is recommended in the application. Here, the cleaning detergent is applied first, and then it is washed off at high pressure after the application time. However, when selecting the cleaning detergent, both the quality of the surface and the statutory provisions should be observed.

Natural and artificial stone exists in acid-sensitive variants (marble, dolomite, travertine, jura, Solnhofen slabs, calcareous natural stones, as well as cementitious artificial stones) and acid-resistant variants (granite, slate, bricks, tiles, clinker). Pressurized hot water or steam can generally also be used on artificial and natural stone. However, the cleaning detergent must be alkaline or neutral for surfaces that are sensitive to acids. Before starting the work, it should be noted whether the material is porous (i.e. absorbent). If this is the case, the surface should be watered down before the detergent is applied as it may penetrate the material and cause damage.

If the surface is very sensitive to water or the contamination is particularly severe (e.g. graffiti), dry ice is very effective in achieving the desired cleaning result in a fast and gentle manner.

Pressurized hot water, often in combination with the steam cleaning stage, is recommended for plaster facades. The method is gentle and achieves excellent cleaning power. However, too much time should not be spent working on one spot in order to avoid dissolving the paint. A flat jet nozzle has proved to be successful with the use of high pressure for protecting the surface as the selective pressure does not become too high at the correct working distance.

In each case, the user should clean from top to bottom so that drops of wastewater that end up in the cleaned area do not arise. The very short drying times of both methods mean that subsequent work can be carried out directly afterward. A neutral cleaning detergent can be used if required to remove soot and oils. It is possible to use a slightly alkaline detergent for finishing coats.

Wood is probably one of the longest used facade materials and is still very popular today. Untreated wood quickly shows weathering effects; treated wood is protected against weathering with additives such as nano particles. This coating must be renewed regularly in order to retain the uniform appearance.

Anyone who wants to restore a homogeneous look to untreated wooden facades can achieve excellent results with a hot water pressure washer. However, care must be taken to ensure that the facade is completely sealed or components that lie behind are not damaged by the water. A frost-free period should also be chosen for the work so that the wood can dry sufficiently after the cleaning. In the case of robust hardwood facades, a pressure of 1450 psi and a temperature between 140 and 175 °F have proven effective. For more sensitive timbers, such as larch or spruce, a pressure of 725 psi is recommended.

In order to improve the cleaning result a neutral cleaner can be used for wood.

Metal facades also require regular cleaning. Aluminium stands out with the formation of a natural oxide layer which protects against corrosion. For anodized aluminium, this oxide layer is created artificially whereby the material is particularly hard-wearing. However, the surface is vulnerable to chemicals, from both acids and lyes. In order to prevent damage, neutral cleaning detergents are recommended. In advance, a sample area should be created and reference measurement be realized before and after the cleaning.

In the case of coated or painted metal facades, it is necessary to remove the so-called chalking (white stains due to washed out pigments). In order to tackle this unpleasant appearance, cleaning detergents with grinding additives, as well as suitable facade pads, can be used. The work is carried out manually or with the support of electric, hand-operated polishing machines. Anyone who wants to use high-pressure technology for cleaning should use natural hair or polyamide brushes (fixed or rotating). Only low-pressure water flows out through the large opening at the brush. Thus, there is no risk that the high-pressure water penetrates the insulating layer behind the facade.

Requirements and regulations

Know what's right:

Requirements and regulations.

Facade cleaning always takes place in the public arena, meaning it is important to obtain information about the requirements and regulations which vary from place to place and from country to country. Wastewater discharge is subject to approval in each case. If it is only dirty water, the water can be discharged after filtration. The solid materials collected must be disposed of. If a cleaning detergent was used, the water must be collected, filtered and neutralized. Also, with regard to the use of spray detergents, the occurrence of dust, noise or exhaust gas, the corresponding regulations must be observed.

Hot water pressure washer

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