Natural stone is an exemplary material when applied outdoors on building façades. It characterizes the architectures conferring an evident aesthetic value, improves thermal insulation, preserves the walls insulation and finishing layers reducing the need to carry out maintenance interventions over time.
The merit of this is in the excellent properties of stone in response to mechanical stresses and chemical aggressions produced by rain, wind, frost and other atmospheric agents; in the low thermal transmittance values; in the guarantee of inalterable colour even when exposed to solar radiation.
The application of natural stone on walls requires professional installation together with a careful preliminary design in consideration of the burdensome loads and the stratification of the walls, with particular regard to the support layer on which the stone will rest.
A substantial difference between STONE COVERINGS that are supported by another load-bearing structure (for example a brick-cement wall or reinforced concrete wall) and the self-supporting STONE WALLS must be taken into consideration.
The merit of this is in the excellent properties of stone in response to mechanical stresses and chemical aggressions produced by rain, wind, frost and other atmospheric agents; in the low thermal transmittance values; in the guarantee of inalterable colour even when exposed to solar radiation.
The application of natural stone on walls requires professional installation together with a careful preliminary design in consideration of the burdensome loads and the stratification of the walls, with particular regard to the support layer on which the stone will rest.
A substantial difference between STONE COVERINGS that are supported by another load-bearing structure (for example a brick-cement wall or reinforced concrete wall) and the self-supporting STONE WALLS must be taken into consideration.
SURFACE-MOUNTED STONE COVERING
The STONE COVERING is the exposed stone which is the finishing layer of any wall or structure that guarantees a load-bearing and supporting function, as well as the relative bedding layer that allows its adhesion.
The covering is therefore of the supported type being constituted by low thickness stone ashlars, usually having sawn back, applied by means of a suitable adhesive directly to the surface of the wall or to a reinforced plaster i.e. a special support layer made of adhesive and a reinforcement, mechanically anchored to the load-bearing layer and which will support the entire "weight" of the stone covering, by the cutting action
EXPOSED STONE WALLS
A STONE WALL is a masonry of self-supporting type , isolated or erected leaning on any other masonry or structure, made of stone and whose "weight" is borne vertically by the foundation placed at the bottom of the masonry.
Walls with a single surface(or head or face) made of exposed stone, consist of solid ashlars placed one above the other, bedded with cement mortar in support of any other masonry or structure that usually has a supporting role for the mechanical anti-tipping clamps.
Stone walls with a single face can be built even in the absence of retaining wall when the ashlars are positioned directly against a rocky or soil slope, for example for the construction of terraces or cliffs(stone retaining walls with dry installation) or by interposing a reinforced concrete bedding layer between stone and slope (stone retaining walls with cast-in-place); they are usually made with a typical shoe profile using larger stones on the bottom and gradually smaller stones as they go up in altitude.
Insulated self-supporting stone walls consist of two surfaces (or heads or faces) made of exposed stone spaced apart from each other and erected by stacking solid ashlars that act as a formwork for containing a cement concrete casting. Also known as rubble masonry these are often used for the construction of boundary walls, whether they are low with fences installed on them or high to obstruct the view.
CORRECT APPLICATION
For the correct application of the above mentioned installation systems it is of fundamental importance to rely on professionals in the stone sector who are able to assess the specificity of individual cases, relating in time with the designated designers in order to find the best solutions and apply the necessary technical expedients.Some of the many technical expedients to be adopted for the correct execution of a work in natural stone are listed below:
- For self-supporting STONE WALLS it is absolutely necessary to use clamping devices at most every 3 meters of height at the slabs level as well as in the presence of specific architectural elements such as windows architraves or beams of horizontal spans especially if they are large (garage doors, overhanging volumes, etc.). The next operation consists in fixing some clamps in the load-bearing layer. The clamps are made of threaded rods or iron rods, suitably shaped in order to allow the direct coupling to other iron rods that act as connectors for more pieces of iron rods previously grafted and blocked by means of a chemical binder to each stone piece. This clamping structure will be drowned in the bedding behind the stone surface remaining hidden and invisible. It is advisable to fasten a reinforcement (for example an electro-welded iron mesh 10x10 cm) to the clamps fixed to the load-bearing structure and drowned in the cement mortar of the stone bedding layer
- For STONE WALLS with cement mortar bedding placed on houses or confined living spaces, it will be appropriate to set up a vapour barrier spread over the entire support wall and located upon a bituminous sheath positioned at the base of the masonry, the latter must start horizontally from the foundation of the paving and bound back for a height of at least one metre.
- For all COVERINGS and STONE WALLS it is always preferable to have the covering upon the paving and not vice versa, with the aid of support curbs or other devices it will be possible to achieve this even if it is required to first create the vertical covering and then the paving.
USEFUL INSTALLATION THICKNESS
For the construction of a stone wall or covering it is necessary to provide an adequate thickness useful for the installation of the Natural Stone and its bedding:STONE WALLS of supported type made of low-thickness stone blocks bond to the supporting masonry, require an ordinary installation thickness ofapprox. 5 cm.
STONE WALLS with exposed stone of self-supporting type made of solid stone ashlars placed adjacent to a masonry, require an ordinary installation thickness of approx. 15 cm (minimum 12 and maximum 25 cm).
Self-supporting insulated STONE WALLS with two exposed faces made of solid stone ashlars and a central binding layer in cement concrete, require an ordinary installation thickness of 35 cm (minimum 30 maximum 50 cm or more depending on the reference height and the size of the ashlars).