Making your own mortar
In a plastic trough, mix 10 parts fine sand for 3 parts lime and 2 parts white cement, or 3 parts fine sand and 1 part lime.
You can vary the proportion of lime, while respecting the final dosage. Make tests with small quantities to check the shade obtained.
Indeed, the color of the sand is essential if you want to get as close as possible to the shade of the stones…
It is not excluded to add a hint of natural pigment to tint your mortar, it's all a matter of taste.
To strengthen the qualities of the mortar, you can also add an additive:
- a fluidifier (or plasticizer) that facilitates machine application,
- a liquid hardener that will further limit dust,
- an expansion product that limits shrinkage.
Sand quality
Preferably use a quality river sand for coating with particle size 0 to 3mm max (quarry sands have grains with angular shapes that tend to create blockages).
Implementing a render
Render is the last layer before any painting of masonry. Its main functions are to protect walls from bad weather and ensure good insulation. Several application techniques are possible depending on the desired finish and performance.
Render is an integral part of house construction. Indeed, render is a finishing layer that protects walls from bad weather while allowing the house to breathe. Besides its wall protection function, render also plays an important role in thermal and sound insulation of the building. Its uniform, often light color provides pleasant aesthetics to the house while reflecting light.
The different techniques
Render application can be done using 4 techniques: sprayed, scraped, crushed, troweled. The chosen technique depends on the desired finish.
Sprayed render
This is the most commonly used technique for protecting large buildings as its cost is significantly lower than other techniques. It consists of spraying the material using a special machine. Implementation is particularly quick for a raw finish.
Scraped render
This technique follows the previous one but adds a second step: the concrete is sprayed then scraped either with a scraping rule or with a nail float. Implementation is logically longer than in the sprayed technique but the finish is more uniform. Scraping tools eliminate any excess material.
Crushed render
This technique like the previous one requires two steps. The first phase consists of spraying the mortar on the wall then while the material is still fresh, a smoothing tool is passed over the mortar to crush it. The effect obtained is quite aesthetic as the wall takes on an uneven moiré appearance.
Troweled render
This technique is most often used by traditional mason craftsmen. It consists of spraying the mortar on the wall then troweling it to obtain a smooth finish. The disadvantage of this technique is that it takes a lot of time to complete and therefore costs quite expensive. Walls made with this technique must be finished entirely in one go or risk seeing large shade differences once everything has dried.
Prerequisites before rendering
Whatever technique is chosen, rendering cannot be done immediately after work is completed. A one-month delay is recommended so that the masonry has had time to dry and stabilize. Walls must be perfectly clean: cracks filled, moss and mold treated. These precautions are all the more important when it comes to renovation.
Render application must be done in specific weather conditions. Temperature must not be above 35° or below 5°. The substrate must be moistened if temperature is too high to avoid cracks and render detachment.
Which compressor to choose for spraying?
Using the CCJ Sprayer or Projoint 2.0, in spray mode, uses little compressed air, as the worm screw does most of the work; Setting between 2 and 3 bars pressure, and about 80 liters of air delivered per minute.
All commercial compressors meet this specification, however, the larger the tank, the greater the air reserve, and therefore the less often the compressor will start.
Minimum 20 liter tank recommended.