What facade impregnation gives
An absorbing wall is the source of many problems. Moisture encourages algae and moss, worsens the insulation and accelerates the decay of the render, and in winter there is the risk of frost damage. A water repellent impregnation makes the water run off the surface instead of soaking in.
The effect is twofold. The wall gets dirty more slowly and turns green less often, and at the same time it copes better with rain and frost. This matters especially on facades exposed to driving rain and on the sides where the wall stays wet for a long time.
Why breathability matters
A good facade impregnation limits water getting in from outside but does not seal the wall tight. The render must still be able to release moisture that ends up in the structure. A product that forms an impermeable layer can trap moisture inside and harm rather than help.
Tip
When choosing a product, check in the description that it keeps the breathability. This feature distinguishes a facade impregnation from a sealed coating and has real meaning for the durability of the wall.
When to impregnate the facade
The product goes onto a clean and dry wall, above freezing and when no rain is forecast during the drying time. You will find the exact range of conditions on the product label. Avoid working in full sun and heat, because then the product evaporates before it can penetrate.
A good time is warm, stable weather in spring or autumn. Remember that after rain or washing the wall needs time to dry deep down, not only on the surface.
Preparing the wall
Impregnation only makes sense on a clean facade. Dirt, green deposits and streaks have to be removed first, because the product highlights and seals in everything that stays under it. How to clean the facade thoroughly we describe in the guide on cleaning a facade. The general rules of surface preparation we have gathered in the guide on preparing the surface.
After cleaning the wall must dry thoroughly. Only then is it worth moving on to impregnation.
Impregnating the facade step by step
- 1Clean the wall and let it dry. Remove deposits, streaks and dirt and let the facade dry thoroughly. This is the condition for effective impregnation.
- 2Protect the surroundings. Cover windows, sills, doors and plants by the wall from contact with the product.
- 3Do a test. Apply the product to an inconspicuous spot to judge absorbency and a possible change in look after drying.
- 4Apply the product evenly. Work so the product covers the whole surface without gaps and streaks. An absorbent render may need more product.
- 5Apply a second coat if needed. On very absorbent renders two coats are sometimes applied. The number of coats and the interval is on the label.
How much product you need
Consumption depends on the absorbency and texture of the render. A rough wall takes more than a smooth one. On the data sheet of each product we state the coverage in square metres, and the calculator converts the wall area into litres. If you plan two coats, take that into account when buying.
The most common mistakes in facade impregnation
- Impregnating a dirty or overgrown wall, which seals the problem in.
- Applying to a damp render, which leads to streaks.
- Choosing a sealed coating instead of a breathable impregnation.
- Working in full sun or just before rain.
- Skipping the test on difficult or coloured renders.
Frequently asked questions
Does the impregnation change the colour of the facade?
Water repellent impregnations usually do not visibly change the look, but on some renders they can slightly deepen the colour after wetting. It is best to judge this with a test in an inconspicuous spot.
Does an impregnated wall still breathe?
A good facade impregnation limits water getting in from outside and keeps the breathability, so the wall still releases moisture. This is important, so choose a product clearly intended for facades.
How often should I refresh the facade impregnation?
The signal is the return of water absorption, that is the moment water no longer runs off and soaks into the render. How quickly this happens depends on the exposure and the product, so you will find the durability on its data sheet.
Does impregnation replace insulation?
No. Impregnation protects against water getting in and makes care easier, but it is not thermal insulation. It does, however, help keep the structure in better condition.
