Before analyzing a recent concrete case, let’s look at the notion of technical volume. According to administrative jurisprudence(1), the technical volume is characterized by:
- the absence of any functional autonomy, even just potential;
- a relationship of necessary instrumentality with the use of the building as strictly necessary to contain, without possible alternatives and in any case for a completely limited volumetric consistency, the technological systems serving a main building for essential technical-functional needs of the same and which cannot be placed, for any reason, inside the same, such as, for example, those connected to the water, heating, elevator and similar pipes.
Further specifications
It was also specified that for the identification of the notion of “technical volume”, three orders of parameters take on value:
- the first, positive, of a functional type, relating to the relationship of necessary instrumentality of the artefact with the use of the construction to which it is connected;
- the second and third, negative, linked on the one hand to the impossibility of different design solutions, in the sense that such buildings must not be able to be located within the residential part, and on the other hand to a relationship of necessary proportionality between such volumes and the needs actually present (2).
The technical volumes, for the purposes of exclusion from the calculation of the allowable volume, are therefore exclusively the volumes strictly necessary to contain and allow access to those technical systems indispensable to ensure the living comfort of the buildings, which cannot, due to technical requirements of functionality of the systems, be incorporated within the body of the construction which can be built within the limits imposed by the urban planning regulations.
The technical volumes of buildings are excluded from the volume calculation provided that they do not take on the characteristics of a closed, usable and habitable space if they are of such a height and volume that they can be used as habitable rooms.
A recent concrete case
Applying the above principles, the TAR Marche, section. II, in the sentence. 7 November 2025, n. 902, stated that this can be considered a space of approximately 2.5 m2, intended to house a heat pump for the air conditioning system, a suction system for the centralized system and a water purifier; said space, in fact, could be considered:
- in relation to the necessary instrumentality with the use of the construction,
- proportional to the needs to be satisfied (placement of electrical, hydraulic, heating or elevator systems),
- of modest dimensions.
Case studies
Among the case law on the subject, we remind you that the following technical volumes have been considered:
- a structure with dimensions of approximately 6 m. x 6 m., height of 1.80 m., without windows, erected on the flat roof of a pre-existing building, having the function of protection, thermal insulation and energy containment as well as housing the technological systems serving the house below(3);
- an electrical substation(4);
- a room strictly functional to contain the staircase connecting the various levels of a building, having a serving and instrumental function for the use of the individual housing units and being equally insusceptible of use for different purposes (5);
On the contrary, they do not fall into the category:
- a room used as a storage/warehouse which is accessed by a glass and iron door and inside which some fridge furniture with display cabinets have been positioned “functional for outdoor grill-barbecue activities”, “located in an area at a considerable distance from the central body of the hotel’s catering services”(6);
- a masonry building consisting of two rooms (bedroom and toilet) under construction, finished internally and externally to the cottage where the preparation of the electrical and water systems is underway (7);
- an attic accessible via a trap door and practicable (as it is internally 1.55 m high), without technical systems (8);
- a habitable room, even if designated in the project as a technical volume (9).
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Notes
(1) TAR Tuscany, section. III, sentence. 7 June 2022, n. 761; Council of State, sec. IV, sentence. 23 July 2025, n. 6559; section II, sentence. November 29, 2024, n. 9581; section V, sent. 4 November 2024, n. 8720; section VI, sen. 24 January 2022, n. 467; TAR Campania, Naples, section. V, sent. 3 July 2024, n. 4099 and sec. III, sen. 6 May 2024, n. 2942.
(2) Cass. pen,, sec. III, sentence. 17 November 2010, n. 7217; sent. 27 May 2016, n. 22255; TAR Campania, Naples, section. IV, sentence. 3 January 2022, n. 35.
(3) TAR Campania, Salerno, sec. II, sentence. 9 December 2022, n. 3333.
(4) TAR Tuscany, section. III, sentence. 15 October 2021, n. 1321.
(5) TAR Puglia, Bari, section. III, sentence. February 24, 2021 n. 329.
(6) Council of State, sec. II, sentence. 10 February 2025, n. 1035, according to which, in the specific case, not only was the close technical-functional correlation of the artefact with the main construction lacking, but also the impossibility of its independent use.
(7) TAR Campania, Naples, sec. VI, sentence. 15 February 2022, n. 1010.
(8) TAR Calabria, Catanzaro, sec. II, sentence. 5 May 2020, n. 807.
(9) TAR Calabria, Catanzaro, sec. I, heard. March 26, 2020, n. 503.
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