The first historical solutions against soil humidity
There is no longer any evidence of the original constructions on stilts from the Neolithic era, as they are easily deteriorated artefacts, such as the wood of the poles exposed to the elements. Of these ancient buildings there remain only a few testimonies on the rock engravings of the upper Val Camonica, in the province of Brescia, temporally dated between 5000 and 10000 BC
Of the foundations of the buildings built in stone, buildings from the Nuragic, Etruscan and medieval periods remain as evidence, up to the present day, in some buildings from the 19th century, before the advent of reinforced concrete.
In Roman times there is evidence of a sort of ventilated crawl space resolved in two solutions:
- moving the floor of the house away from the bare earth, with the positioning of terracotta amphorae in the layer under the walking surface, placed side by side, filling the spaces between them with gravel and stone, with a draining function;
- building an empty space, with the floor raised from the ground and supported by stone walls (suspensurae) or bricks, with the function of creating a horizontal heating system (hypocaust) in which the heat produced by the combustion of wood was distributed. This system was the progenitor of that construction solution which many centuries later would become the cat flap, but without the heating system.
From construction knowledge to the first building regulations
In more recent times, in some cases the detachment from the ground of the first or mezzanine floor is solved by adopting a draining crawl space, i.e. fillings of gravel and crushed stone under the floors. In other cases by adopting the cat flap, a modus aedificandi that takes us back to the Roman era as described above, but with some elements of codification dictated by the first construction regulations.
Of what we define as a ventilated crawl space, we still adopt today the first and only regulation that described the basic construction rudiments, with four simple articles. This is the Ministerial Institution of 20 June 1896, later updated with the Ministerial Decree of 5 July 1975 and which, with the original articles 56, 57, 60 and 61, dictates the first very simple rules for separating the ground floor from the ground, through the formation of an empty volume under the floor, no less than 40 centimeters high, duly ventilated and with the load-bearing structures waterproofed to the supports earth.
The technical evolution of the modern crawl space
Nowadays, although various advanced solutions now exist to solve the problem of humidity from the ground, the ventilated crawl space remains in Italy as “the solution”, referred to in most local and regional building regulations, but with different descriptive methods from place to place.
In the absence of a specific standard and a complete and exhaustive technical corollary that describes the construction technique, today’s ventilated crawl space is affected by the technical evolution of the early 90s of the last century, which saw the commercial introduction of the most widespread construction method today for creating a sanitary void, adopting special disposable formwork. This system, patented by the Daliform Group company in 1993, with the commercial name of “Iglù”, is composed of polypropylene plastic elements, partly recycled, of various shapes and heights which, placed side by side, constitute the base and support for creating the structure of a load-bearing floor.
The distribution along the side walls of special opposing openings therefore constitutes the necessary ventilation, which, if it guarantees correct convective ventilation, allows the maintenance of dry air under the floor, thanks to the air vacuum and the ventilation openings uneven between them, between the entrance and exit.
With the regulatory evolution of twenty years ago and the need to obtain particular thermal performance in the building, avoiding thermal bridges and dispersions from the casing, together with the detachment from the ground for hygrometric purposes, the application of an insulating system that falls within specific regulatory parameters, but above all that maintains an internal climate suitable for the habitat, is also required.
Alternative techniques between performance and legislation
As mentioned previously, the ventilated crawl space is not the only solution to the support of the construction on the ground for the thermo-hygrometric resolution. Current construction techniques and new materials produced from the early 1900s to today can guarantee equal and even improved, as well as economic, conditions compared to the ventilated crawl space solution, which however, as mentioned, is still referred to by building regulations as a proven solution.
It is obviously up to the technician’s decision to be able to choose which technique to refer to in order to solve this fundamental problem, even going against the indications of the law, provided that the validity of the alternative system adopted is demonstrated with a simple design description.
