Clay plaster on wood
Wood can never be plastered directly, it always needs a plaster base. The plaster base forms a non-slip surface on which the clay clings in a form-fitting manner. The direct contact between clay and wood is by no means harmful, because the moisture-regulating property of the clay also has an effect here: the wood is perfectly protected because the clay permanently removes moisture from it and thus keeps it dry.
All beams in the framework must also be provided with a plaster base for infilling. Long straw was used here in the past. It was worked into the compartments on the right and left and connected them to one another by spanning the beam crosswise and fixing it in the middle with one or two split hazelnut rods. Nowadays you don't work like that anymore, because the straw can become crumbly and brittle. As a result, these areas are not stable enough. Before plastering wooden beams, it is common today to staple a reed fabric as a plaster base.
to the plaster base for clay plaster
Reed can also be used as a plaster base on other wooden surfaces. Other plaster bases for plastering on wood are expanded metal, Rabbitz mesh, brick wire mesh or hemp fleece, the latter in combination with the matching clay adhesive plaster. Primers on wood are not a sufficient plaster base.
Fastening reeds or other rough plaster supports with a compressed air stapler and suitable clamps is quick and effective.
Cane is also used as permanent formwork to build interior insulation from light clay. Light clay is an optimal and sensible interior insulation for the half-timbered house.
Clay plaster on masonry
It is not very problematic to apply clay plaster to masonry. An important rule is already fulfilled here, namely that the surface is nice and rough. The rougher the subsurface for a clay plaster, the more firmly the clay can cling to it. This is particularly important with clay plasters because they do not form a chemical bond with the substrate, but adhere to the substrate purely mechanically. However, the different bricks are differently suitable as a substrate for a clay plaster. Clay bricks, clinkers, field fire bricks or hollow bricks do not require any further preparation or plaster base for the clay plaster. A clay undercoat plaster is applied directly here.
to the pre-sparay mortar
In the case of mixed masonry in old buildings, it is important to note how absorbent and how rough the subsurface is. In most cases it is possible to apply a sub-layer of clay directly. However, we strongly recommend using a fabric for non-homogeneous substrates. If the old wall is very holey, the recesses are first filled so that the fabric layer can then be embedded in a flat plaster in one operation.
Masonry can also be made of Earth bricks. Earth bricks work wonderfully and are an excellent plaster base.
Clay plaster on gypsum and old plaster
Remodeling or renovation always brings out different fillings or old plaster. Rough and absorbent old plasters such as lime plaster can be plastered with clay; moistening the substrate is sufficient here. A sandy lime plaster can be strengthened with sintered water, bio-fixative or casein. These building materials differ in their mode of action: casein strengthens the surface, sintered water has a weaker and deeper effect and bio-fixative is a classic deep primer with natural ingredients.
Gypsum substrates are always problematic for a subsequent plaster made of clay or lime. Gypsum is organic. Although it absorbs a lot of moisture, it is difficult to release it again. It swells up a lot and is a perfect breeding ground for mold growth. The first recommendation is therefore always to remove the old plaster substrate and make a new plaster build-up. Since this is not always possible, the gypsum must be pretreated with a primer in order to create a new substrate for the subsequent clay plaster. On the one hand, the primer largely blocks the gypsum from moisture, and on the other hand, the surface is rough enough so that the clay plaster can stick to it.
Every manufacturer's plastering system also includes a primer that harmonizes with the other products and should therefore also be used in conjunction with them. Please note, however, that not all primers are free from dispersions and that the use of primers reduces the absorbency and diffusivity of the wall.The granular primer from Hessler Kalkwerke works without dispersion, is reasonably priced and very well suited for these substrates.
*Wallpaper and old, chalky or peeling paint must always be removed despite the use of a primer!
The gypsum fiberboard or plasterboard panels often used in new buildings are cheap and quick to install, but they also have the less than optimal properties of gypsum. A primer must also be used here if a reasonable plaster made of clay or lime is to follow.
An adhesive plaster can be used very well for particularly inhomogeneous old plasters. Lime adhesive plasters, applied with a notched trowel, form the most stable substrate for a stable plaster build-up.
Clay boards as a substrate for a following clay plaster
The easy and quick processing of clay building boards, combined with the short drying time for the subsequent plaster, allows quick and targeted work and facilitates the completion of the building project. The panels can be easily cut to size with a tool such as a jigsaw or circular saw or a cutting disc. They can also be broken over an edge with a cutter after they have been cut. After attaching the clay boards, only a fine-finish plaster with a paint coat or a facing plaster plaster follows.
According to the dry construction method, lightweight clay panels are used for cladding sloping ceilings or ceiling surfaces. Another building element of the family is the heavy clay board, with which a lot of mass can be brought into the building in a simple way in timber frame construction. Storage mass, whether for warmth, coolness or moisture, is important for a healthy home. Here it has to be considered whether the complex pre-production is profitable in relation to the fast assembly.
The perfect multitasking building material is of course the clay building board with integrated wall heating. It combines either infrared radiant heat (in the electric version) or radiant warmth from the hot-water circuit (in the water version) with the structural and climatic advantages of clay and the fast construction method of drywall.
Insulation of the compartments made of hemp or wool: a holistic, healthy wall structure.
The indoor climate benefits of clay only come into play if the entire wall structure is made from ecological building materials. Cavity insulation made of stuffing hemp or sheep's wool harmonises perfectly with all other organic building materials and especially with clay.