- Necessary material
- A "breathable" coating
- A building site with three
- Preparation of the support
- The interest of the "ready to ruin"
- Projection of gobetis and plaster body
- Realization of finishes
- Lime: a powder to do everything
With a machine to project, this coating is worked with a scraper, a trowel or with the sponge. While respecting his style, he protects and embellishes the facade for several decades.
Necessary material200 bags of mortar formulated (here "Restorative plaster" ParexLanko Light Parexal and Parexal)
Over the years, the coatings are less adherent, reveal cracks, crevices or desquamations.
It is then time to bare the walls to apply a new coating.
Why not take advantage of the building site to improve the insulation of the house?
Especially since 25 \% of thermal losses of a house concern the facades.
This choice was made by the owner of this 1930s pavilion.
Without encroaching on the living space, the insulation hemp block insulation (Chanvribloc) has removed the sensation of cold wall in winter and overheating in summer.
In addition, the implementation of this insulation could give rise to a tax credit if it was implemented by a company.
A "breathable" coating
Side facelift, the coating is classic.
The bonding layer, called gobetis (6 mm thick), forms a part of the hemp blocks.
It consists of aerial lime (65%) and hydraulic lime, fine sands and mineral additives (ParexLanko, Weber...).
After two days, a second layer (plaster body) is applied (10 mm thick).
It removes surface unevenness and ensures the flatness of the coating.
After 24 hours, the top coat brings the final appearance and color.
These two passes consist of natural hydraulic lime, sands, mineral additives and mineral pigments (here ParexLanko's "Parexal").
A building site with three
Thus formulated, these renovation coatings do not require any preparation (collection of ingredients, dosing and dry mixing).
Simply pour the bag into the blender and let a certain amount of water run (depending on the type of layer and consistency). The towable unit consists of a 120 liter tank, a compressor and an air flow.
Three people ensure his full performance.
A "spoiler" feeds the mixer by emptying the bags of binder while an operator moves on the scaffolding with the lance to project the coating.
Another erects the layer deposited as and when.
As for consumption, it takes on average 14 kg / m2 for 1 cm thick.
Preparation of the support
A hexagonal wire mesh is attached to the hemp blocks constituting the outer insulation.
It favors the grip of the first layer of plaster.
The blocks are slightly moistened, shortly before application of gobetis.
The projection lance must be held horizontally and with both hands.
The bags of mortar are torn on the protective grid of the mixer and poured into the tank of the projecteuse.
Depending on the porosity of the substrate and the ambient temperature, the water dosage can range from 5.5 to 6.5 liters for a 30 kg bag,
The interest of the "ready to ruin"
The formulated mortar contains in the same bag the binder and the aggregate.
Dosing, calibrated and mixed in the factory, it combines lime, plaster, sand, mineral fillers, additives and pigments. It only remains to add water!
More cost-effective than a standard basic binder, it offers undeniable advantages: simplified preparation (no more dry mixing in the concrete mixer), regular dyeing and dosing, specific composition and granulometry designed for application to the spraying machine (between 8 and 30° C).
Projection of gobetis and plaster body
The fairly fluid paste is projected from top to bottom in horizontal or vertical passes, depending on the recoil available on the scaffolding.
A nozzle allows the flow rate to be adjusted and stopped if necessary.
The angles are treated by vertical passes.
The mortar beads should overlap to avoid any mortar.
The facade and the sides of the central dormer are coated following the same method (with some contortions!).
Spread with a small board, the mortar is tightened with the back of the trowel or a smooth stainless steel.
The second tinted layer forms the thickness of the coating.
As before, it is applied by spraying (10 mm thick) taking care to cover the surface of the gobetis uniformly.
The mortar is leveled with the board and then with a notched ruler.
If the binder sinks in places, it must be tightened upwards.
Semicircle movements with a trowel make it possible to obtain a plane wall.
The hollows are filled with mortar pads.
The roofing of the skylight requires the presence of two people, secured by a harness and positioned on both sides: one projects the plaster, the other tightens it and equalizes it with a trowel.
Realization of finishes
After 24 hours, the plaster is scraped by making circular movements.
The minimum thickness should be anywhere from 8 mm after scraping.
The surrounds of windows and doors are treated with a comb gratton that allows scraping the less accessible areas.
Slightly tilted, this tool also helps to finalize the fittings.
The tables of the bays are belted with cleats to guide the plumb.
After removal, the edges are trowelled.
After 24 hours, the third layer is projected on 8 mm thick, then equalized with the smoothing.
Just after the start of the setting, the surface is smoothed with a wet sponge float, touching without pressing.
The smoothing with the trowel foam is carried out from top to bottom by using as visual references the banks of the roof and the intersections of the walls.
The trowel is regularly dipped in a bucket of water to keep it clean.
Lime: a powder to do everything
A universal binder, lime has been used since ancient times. Real natural mineral glue, it is obtained by baking limestone rocks.
Its characteristics are therefore very close to those of stone.
Microporous, it is, with plaster, the only binder compatible with traditional masonry, whose hygrometric balance it respects.
Melted with sand, lime forms soft, creamy and very adherent coatings.
There are airless lime (CL) and natural hydraulic lime (NHL).
Produced with very pure limestones (containing less than 5% of clay), the first hardens only in contact with air.
This hydrophobic nature is not very compatible with the weather.
It is often used for whitewashes and plaster finishes.
The second is obtained with "clay" limestones (10 to 15%), which give it its hydraulic properties.
Its grip is quite fast even in the presence of moisture. Except in special cases, it should not be associated with cement since it already contains!