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The National Technical Approval (DIT) is a voluntary document which is issued by the Eduardo Torroja Construction Sciences Institute (IETcc). This document contents the favourable technical assessment of the fitness for use of non-traditional or innovative materials, products, systems or procedures in building and/or civil engineering.

The IETcc is the only Spanish Organization which awarded, by Decree 3652/63 of Presidency of the Government dated December 26, 1963 and Ministerial Order1265/88 dated December 23, 1988, the faculty to grant a DIT as well as the confirmation of others DIT which had been issued by other members of the European Union of Agrément (UEAtc).

Construction reports magazine
cover page N.110.

“How can new materials take part in construction until people who know about design, construction or maintenance understand them?”.

  Frank Lloyd Wright 



Those materials, systems or structural methods that have not regulation about their characteristics or product performance like operating instructions it may be a subject to DIT. In addition, the following conditions need to be fulfilled:
• Industrial materials and systems or methods that have been used in real applications.
• Perfectly identifiable materials or systems.
• Materials or systems that are intended for a specific and unmistakable use.

The DIT for a material is issue for a specific use. If the material has different uses, it will be necessary a different DIT for each one.


The issuing of the DIT is based on the favourable assessment of the performances of the product for the intended use, facing the requirements of:
• Mechanical resistance and stability.
• Safety in case of fire.
• Hygiene, health and the environment.
• Safety and accessibility in use.
• Protection against noise.
• Energy economy and heat retention.
• Sustainable use of natural resources.

The issuing of a DIT takes also into account the favourable behaviour facing global demand of durability, the inspection of the manufacturing plant and of the factory production control by the manufacturer, as well as his commitment to provide technical assistance to the construction site.

«Torroja has expressed the principles of organic construction better than any other engineer».
Frank Lloyd Wright.
(Conf. in Pittsburgh y note for Philosophy of structures).

Building with a ceramic cladding system granted with DIT
(Casablanca, Marruecos)

Building with a hpl cladding system granted with DIT
(Student residence, South Essex, UK)

DIT cover (DIT N.º1)


 2º DIT cover (DIT N.º2)

First cover with DIT logo

Current DIT cover



The DIT develops at least the following aspects:
• Product principle and description.
• Materials that compose it.
• System elements or components.
• Manufacture.
• Internal and external controls on manufacturing and commissioning work.
• Transport and storage conditions.
• Commissioning process and conditions.
• Use references of the system in real cases.
• Identification, usefulness and durability tests.
• Positive assessment standard for usefulness and calculation methods.
• Advice and suggestion of the Expert Commission for each DIT.
• Construction details, particular points, etc.

DIT 391 – System for Emergency Temporary Housing (ETH)


The DITs are valid for 5 years and, during this period, annual surveillance is carried out. After the validity period, the manufacturer must apply for the renewal of the DIT.
The surveillance to be carried out shall fulfil the Regulation for the surveillance of DIT, provided for this purpose. If the annual surveillance result as favourable, the IETcc will issue an annual certificate, which shall be linked to the DIT in order to maintain its



A DIT issued by an Institute member of UEAtc can be validated in any of the UEAtc members through a bilateral procedure called Confirmation (UEAtc Rule 03 and 04).
This method is not automatic, since it is necessary to consider for the new DIT, the particular characteristics (regulations, weather, etc.) of the destination country. However, it may allow a significant reduction in costs and time.


This procedure is a multilateral method involving more than 2 Institutes (UEAtc Regulation 05) that allows the simultaneous granting of the DIT in several countries
The Institute that receives the request coordinates with the other Institutes the preparation of a document made up by a general part and the complementary parts required by different countries regulations.


This document is a bilateral procedure for granting DIT between Italy and Spain (currently), which gives to the manufacturer the possibility of obtaining the DIT in both countries at the same time. This DIT is published in both languages in a single document.This document is a bilateral procedure for granting DIT between Italy and Spain (currently), which gives to the manufacturer the possibility of obtaining the DIT in both countries at the same time. This DIT is published in both languages in a single document.

Structure with DIT.
(Shopping centre, Málaga)