Air pollution, rain or even just the soccer-loving kids – a house facade has to cope with a lot. Every now and then, however, the exterior walls need a fresh coat of paint. No problem for a skilled do-it-yourselfer.
The facade is, to put it poetically, the face of a house or, more profanely, the outer skin of a building. It inevitably ages, as it has to withstand wind and weather for years. And that’s why a facade coating has to be renewed at some point – after 10, 20 or 30 years.
Repainting the facade: Failure analysis
The occasions to repaint a facade range from harmless to serious. Blemishes do not affect the building itself, but only its appearance: Dirt particles, dirt splashes, fading, drip noses at the drainage points of window sills or the colonization of areas with green algae. If, however, these visual defects are joined by minor cracks, flaking paint or even holes, then the answer is: first renovate the facade, then paint it.
Color selection for the new coating
Choosing means deciding:
- Should the house have just one color?
- Or would you prefer two shades, so that, for example, the flaps, i.e. the edges of the windows and doors, can be set off against each other in color?
Before starting work, do-it-yourselfers should be sure to check whether there are any municipal or state regulations governing the design of the facade. According to the Building Code (BauGB), an owner must always and literally have the townscape in mind. For example, if a coastal town is dominated by white houses, another color may be considered out of place. If pastel tones predominate in the town, neon green or navy blue might be out of line and potentially prohibited.
In addition to the hue, homeowners also need to choose the color type. These include:
Silicate paints
Their main ingredient is potassium silicate, commonly called water glass. The binder bonds with the substrate by silicification and reacts alkaline, which especially prevents the formation of algae on the facade. The paints are breathable and very weather-resistant. They are particularly suitable for mineral substrates such as lime plaster, fiber cement or concrete – in particular porous substrates. Only dispersion silicate paints, which additionally contain a synthetic resin dispersion and are thus suitable for heavily attacked substrates, provide even higher quality.
Polymer resin paints
They do not contain water as a solvent, so they differ from water-thinnable emulsion paints. The binder is usually a mixture of various synthetic resins. The paints form a film that looks matte when dry, which also gave it the name “facade matte paint.” Advantage: the paint can be applied even in cold weather, because it does not contain freezing water. However, the paint is not suitable for insulating plasters with polystyrene components because of the organic solvents.
Dispersion paints
They are the most widely used today because they are easy to handle: water-thinnable, easy to spread, enormous variety of colors, inexpensive. Their components are not dissolved in water, but only very finely dispersed – which is called dispersion. The disadvantageous effect: after a long storage time, these microscopic particles settle on the bottom. Therefore, before painting dispersion paint must be vigorously stirred until it is homogeneous again.
Lime paints
They are rarely used today, for example in stables and on facades made of lime plaster. They can be painted directly onto the still fresh plaster. In addition, this paint is extremely inexpensive because it consists only of lime and water; sometimes it also contains glue, chalk or gypsum. However, it may wash out in driving rain.
Casein paint
Basically, it contains only water, coloring pigments and casein as a binder, which we know from low-fat curd cheese. Chalk or various rock flours are often added to thicken it. Enthusiasts can buy all the ingredients and make the paint themselves. You will hardly find the product in hardware stores, but you will find it at ecologically oriented specialty suppliers.
Lotus paints
This name can be given to almost all paints that have a special property: the so-called beading effect, which is copied from the lotus flower. Special additives make the surface of the facade highly water-repellent; rain runs off in rivulets. This washes away small particles of dirt, which is why such coatings are said to have a self-cleaning effect.
Have tools and materials ready for the new facade coating.
Some people swear by the classic paint brush, also known as a tassel, while others prefer to use a roller or paint roller. No matter which tool the do-it-yourselfer ultimately chooses – the quality is crucial. Otherwise, you will have to constantly pick individual bristles off the facade. In the case of very heavy coats of paint, the brush can also clump. A solid lambskin roller is always recommended, while plastic rollers are usually only suitable for thin-bodied paints.
Other indispensable tools include a medium-sized flat brush for the edges and, of course, tape plus a tarpaulin to mask off adjacent components. In addition, a bucket with a scraper grid, garden hose or high-pressure cleaner.
If the facade is in need of repair, additional tools are needed for the renovation: putty knife, wire brush, repair putty for exterior use, small chisel if necessary, hammer and smoothing trowel.
Mastering the height: ladder, scaffolding or flying armor
In principle, there are the following ways to get to the upper part of the facade:
The traditional tubular scaffold. It is supplied by specialized scaffolding companies and erected and dismantled in a customized manner over the entire facade. Often roofers can also help out. You then usually pay a flat rate or the rental days are calculated. In some cases, scaffolding can only be rented on a weekly or even monthly basis. The costs are in the thousands, but for that you don’t have to worry about anything and can work safely and comfortably.
If you want to get up high more often, you can buy a so-called ladder scaffold at the nearest hardware store. It usually consists of a basic module that can be upgraded in the sense of the word, i.e. widened or raised with additional parts. Basic models cost between 300 and 400 euros. With them, you can only paint in sections, so you have to move up each time. On the other hand, most DIY scaffolds have rollers on one side to make this easier.
Experienced do-it-yourselfers can build a flying scaffold. For this purpose, usually the reveals and parapets of the upper windows or supporting beams on the roof overhang are used. Ropes or metal brackets are anchored there. The running or working boards are then placed on the brackets or hung from ropes. Such constructions were once in use as a substitute for scaffolding, but are not recommended for inexperienced amateurs.
Painting the facade with a simple stepladder is conceivable, but it is neither practical nor convenient, and it is also dangerous. You should at least support the ladder on both sides and secure yourself with body harnesses. Such fall protection devices can be borrowed from roofers. In any case, the disadvantage is the inconvenient work and the small reachable area. A telescopic extension for the paint roller can help. In addition, the upper edge of the ladder should be padded to prevent damage to the facade when leaning against it.
Prepare the facade
Before painting can begin, the substrate must be tested. Some hardware stores offer so-called facade test kits for this purpose. The price is around 15 euros. With new plaster, however, there is nothing to check; it only needs to be cured or dried. With old plaster, on the other hand, the following things need to be checked in detail:
Have dirt, algae, or specks of grime accumulated?
In the simplest case, hosing down the facade with a garden hose is sufficient. In the case of stubborn dirt, a high-pressure cleaner must be used. The sharp water jet often causes loose paint or even loose plaster to fly off. That’s why you need to be very careful not to cause any new damage.
Is the old paint peeling – even if only in a few small spots?
If so, the old paint must be sanded off generously by hand or orbital sander.
Can sanding be observed?
When wiping with a firm cloth or scraping with a hard brush, you can see whether the surface is still firm. If sand trickles off, the substrate must be treated with facade primer.
Have holes, depressions or cracks formed anywhere?
Fill them with exterior repair filler and apply a good coat of paint. Smaller cracks can also be filled, but should first be widened and generously but thinly covered with surface filler. After that, it is best to apply reinforcing fabric and fill everything over again. If a smooth surface cannot be achieved, the surface must be sanded flat after curing so that the repair is not visible later.
Is the plaster still tight?
This can be determined by tapping the surface lightly with a fist. If it sounds hollow, the plaster is no longer adhering. This may still be possible for a single spot the size of a plate, but for larger stains, the loose substrate must be knocked off. After that, new plastering is required. If necessary, small hollow spots can be covered with reinforcing fabric and filled.
Painting the facade without streaks and color marks
Once the facade is prepared, the first coat of paint is applied. Do-it-yourselfers should follow these tips:
Wait for the right weather
A warm and sunny day invites you to perform work on the exterior facade. But that’s exactly what can backfire: If painting is done when the weather is too hot, fresh plasters on repair areas and water-based paints can literally burn. They are too quickly deprived of the moisture needed for curing. The material then does not hold properly or is completely gone.
Problems can also occur in damp or even wet weather. If you choose a rainy, cool day to paint the facade, the moisture can cause minor cracks. The situation is similar with dew or fog. It is therefore important to avoid particularly warm, cold or damp climatic conditions. Cloudy days with temperatures between 10 and 25 degrees are ideal.
Paint wet on wet
To avoid unsightly streaks or color marks later on, contiguous areas should be renovated in a continuous process, i.e. wet-on-wet. Another principle is that the second coat should not be applied until the first has dried completely.
Painting several times
In order to paint the facade without any gaps, it is often necessary to apply several coats of paint. This is another source of error. If the first coat is not completely dry, this can quickly lead to the dreaded wrinkling.
Some manufacturers of facade paint advertise that only one coat of paint is necessary. However, this is often not the case with light tones on dark substrates. Some emulsion paints provide inadequate coverage. This means that the repaired areas on the facade often show through. A second coat is then unavoidable, even if it was not planned. For do-it-yourselfers, however, the principle applies anyway: it is better to paint twice thinly than to apply too thickly once.
Buy enough paint
The quantities per square meter indicated on the paint buckets usually only apply in the ideal case. You can therefore do no wrong if you buy 10 to 20 percent more paint – especially for rough or textured surfaces.
