Mezzanine: the rules and necessary permits


Emma Potter

The mezzanine is one space-saving solution widely used, both in homes and in garages and cellars. It consists of a defined plan of servicewhich is obtained through the total or partial subdivision of rooms using a support structure which can be made of wood or steel.

Generally, this solution is opted for in the presence of a considerable heightbut this is a need in the domestic context, that is, when the mezzanine has the purpose of creating a room or in any case an additional space in the house.

In fact, everything depends on the intended use of such a structure, that is, whether it should be habitable or if intended to act as deposit for sports equipment, suitcases, Christmas decorations and so on.

The mezzanine can be built on-site or mounted if it is a prefabricated. Depending on the type of mezzanine, there are specific rules to observe.

Mezzanine inside a garage or cellar

The mezzanine that is built inside a garage or a cellar, therefore having a purely function of expanding the space to be used for storing objects, is naturally not subject to the architectural constraints that a mezzanine built inside a building must respect. home.

In fact, the need to respect the height-light-ventilation ratio of the room is eliminated.

Inserting a mezzanine in the garage or cellar is an excellent choice as this structure has a load capacity far superior to that of shelves, cabinets and various shelves.
Furthermore, it takes up less space, as the surface beneath it remains walkable, and contributes more to keeping it in place order the environment.

It can be made with wood, iron, steel and the metal structure is opted for when you need greater capacity to support the weight of the load.

Mezzanine to create an additional room in the home

The mezzanine is an elegant, practical and efficient architectural solution. In fact, the new area created vertically by exploiting the height within the walls of the house allows you to satisfy many different living needs: having an extra bathroom or bedroom, perhaps for guests, even equipping the kitchen here.

Or it can simply be an extension of the relaxation area, a corner where you can read a good book, watch a film and, why not, work in complete tranquility.

This last need has amplified greatly in recent years with the surge in smart working which, however, clashes with the domestic reality of spaces that are sometimes inadequate or overcrowded.
Each mezzanine is connected to the floor below via a staircase which contributes to enriching the interior design.

Clearly, this is the case where it is an absolute obligation to comply with minimum heights and the air-lighting ratio which we will read about later.

The rules to follow when creating a mezzanine

First of all, a necessary premise: there are different regulations that apply in this regard at national, regional and even municipal level.

We have three levels of regulation:

  • National (Presidential Decree 380/2001, Prime Ministerial Decree 20 October 2016);
  • Regional (these are provisions that integrate or modify the Consolidated Building Act);
  • Municipal (regulations that apply based on the specific peculiarities of the municipality, based on its master plan).

All three enjoy a certain autonomy.

We proceed like this:

The Municipal Building Regulations can establish more or less stringent values ​​(as in the example of the height of some mountain municipalities) in full autonomy, as long as they always comply with the parameters indicated by higher level legislation.

For example, if there is no confirmation for a certain value (this could be the case of the height of the mezzanine or the maximum achievable surface area) within the text of the Municipal Building Regulations, the corresponding value provided for in the regional level Regulations can be used. .

And even if the regional legislation does not provide the information sought, it goes back to the national laws.

The reference coordinates that almost all regulations for the design and construction of a mezzanine have in common are the indications contained in the Consolidated text of health laws (RD 27 July 1934 n. 1265 published in the Official Gazette n. 186 of 9-8-1934 and its subsequent amendments with the Ministerial Decree 5 July 1975 and the modification of the ministerial instructions of 20 June 1896 relating to the minimum height and hygiene requirements -main sanitary facilities of rooms used as dwellings, published in the Official Journal no. 190 of 18 July 1975).

If the mezzanine is built at home and therefore performs the function of additional living space, the first parameter to respect is the one relating to height. The minimum heights are the must have in this case, both for the upper and lower parts of the structure.

We must always keep in mind that the minimum useful internal height of the rooms intended for habitation is established at 2.70 metres. It is permitted to go down to 2.40 meters for corridors, hallways, bathrooms and closets.

In mountain municipalities located above 1000 meters above sea level, a reduction in the minimum height of habitable spaces from 2.70 to 2.55 meters may be permitted, by virtue of the specific climatic conditions of the area.

As for the mezzanine, almost all Municipalities have included in their Building Regulations the indication of minimum values ​​for heights. The limit to be respected applies both to the new space created above and to the surface located below the mezzanine.

Generally, these values ​​fluctuate between 2.20 and 2.40 metres.

However, if the Municipality “xy” did not mention the limits for the heights above-below the mezzanine in its regulation and there is no indication of this even in the regional legislation, the designers of this hypothetical mezzanine will have to take the content of the national legislation as a reference.

In the specific example, however, let us remember that the Ministerial Decree of 5 July 1975 establishes that habitable rooms must have a minimum height of 2.70 meters (with the permission to reduce the height to 2.40 meters only for bathrooms, hallways and corridors ). Therefore, in this case the possibility of creating such a mezzanine for residential use could no longer be possible.

Another fundamental parameter to respect is that which concerns the maximum surface area of ​​the mezzanine. This is the width of the mezzanine shelf: generally the regulations in force establish that the latter must not be greater than 1/3 of the total surface area of ​​the environment in which the mezzanine is inserted.

Therefore, the mezzanine must never exceed the habitable area underneath. Only in the presence of considerable heights, above average, can the mezzanine part cover 50% of the total surface.

This is necessary to maintain the adequate surface-natural light-ventilation ratio to guarantee the healthiness of the environment.

In fact, the regulations also provide that in the event that the openings (i.e. windows or skylights) are not sufficient to guarantee a air-lighting ratio greater than or equal to 1/8it will be necessary to create additional ones.
Depending on the specific situation, to replace or support further openings, ventilation systems may be set up to allow the air exchange.

The concept of air-lighting ratio is very important: it is the proportion between the floor surface and the window surface.

For each room intended for residential use, the width of the window(s) must be proportionate so as to ensure that daylight enters the room in an average amount of no less than 2%. And in any case the area covered by openable windows cannot be less than 1/8 of the floor surface.

The necessary permits

The mezzanine for residential usetherefore what we create to expand the usable and walkable space in the house necessarily requires the Permission to build.

This document is essential for the construction of a new building or for the implementation of renovation or implementation works (as in this case) which will bring structural variations to the building. And this intervention involves an increase in the usable walkable surface, as well as a modification of the shape and internal volume.

In this regard, it must be said that the Court of Cassation has expressed its opinion on not subjecting the construction of a mezzanine to the obligation to possess the Building Permit, considering it an internal work (Penal Cassation, section II, 1/4 /1994, Vicini and Cass., section III, 16/2/1990, De Pau).

But we must also keep in mind that various bodies, Courts of Appeal and even the Magistrates' Court of Rome (see for example: Pret. Roma, 17/6/1993, Guadagno) continue to legally consider mezzanines as works requiring a Building Permit, especially when they bring an increase in the walkable surface.

Therefore, it is a good idea to inquire in advance with the Technical Office of the Municipality where the property is located.

As an alternative to the Building Permit, in fact, the Report of Start of Activity pursuant to art. 22, paragraph 3, tu 380/2001.

The mezzanine not habitablei.e. the structure that serves as storage for objects (in the garage or cellar) is classified as a minor intervention and this means that it is exempt from the presentation of the Building Permit or the Declaration of Commencement of Activity.

However, it is necessary to inquire at the Technical Office of the Municipality to avoid incurring sanctions and to find out if:

  • documentation must be produced before building/assembling the mezzanine;
  • the methods for submitting this documentation to the Municipality;
  • which of these declarations is required: SCIA, CILA or CIL.

Let's see what each of them consists of.

The SCIA, that is Certified Report of Start of Activityis mandatory when working on the structural parts and, therefore, in the event that the works to be carried out will involve a structural modification of the building.
The owner of the property must send the SCIA to the SUAP (One-Stop Shop for Productive Activities) of the Municipality and it is possible to do so exclusively electronically.

CILA is the Communication Commencement of Work Affirmed and must be sent before the start of work to the relevant municipality. It concerns extraordinary maintenance interventions that do not imply a structural modification to the building.

The CILA must be drawn up by a qualified technician (an architect, a surveyor) who has the task of certifying the works carried out.

The CIL, which corresponds to Communication Start of Workmust be presented for the execution of temporary works, i.e. those with the aim of satisfying atemporary need and which for this same reason will then be removed as soon as this need ends.

However, the 90 day deadline cannot be exceeded.

The CIL can be forwarded directly by the citizen and certification by a qualified technician is not required as these are simple works that do not modify the structure of the property.