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Detailed design: definition

Detailed design is one of the three stages which are part of the detailed project to which the Italian rules relate for the regulation of design in public works
We have tried to outline below how to define detailed design, starting from the definition of project.The reference to public works is due to the fact that in their regulations there is the exact definition, but what the detailed drawing actually is and means is valid also in the relationship between private individuals.It makes no distinction in this sense the British planning tool - the 2013 Work Plan of the Royal Institute of British Architects - in which the analogue of the detailed design is the Technical Design.

The drawings, according to the Italian normative reference, are those which:

  • Develop all the drawings of the final design in the allowed or prescribed scales;
  • are necessary for the execution of the works;
  • contain all the details of construction and the manner of execution of details;
  • conform to the requirements laid out by the competent bodies in the preliminary and final approval of projects;
  • meet the standards of size and cost in order to ensure the utmost respect and full compatibility with the features of the local context and environment in which the action is set;
  • describe the features of size, performance and assembly of prefabricated components;
  • define the phases of construction passed to the structure;
  • have been redacted in such a way as to allow the performer a reliable interpretation and execution of the works in their entirety.

From the detailed drawings are excluded the operational plans of the site, the procurement plans, the calculations and graphs concerning provisional works.

Effectiveness of the detailed design

When we face detailed design, we develop a story starting from the final project, consisting of drawings already approved by the competent bodies and often already contracted to the construction company.
Our work will be concurrent with that of other professionals - structural, mechanical, electrical engineers - who will provide shop drawings of structures and facilities.
We also think of the detailed design as a tool to communicate, both with businesses, suppliers, workers who contribute to the construction of the building, and with the other professionals involved in the design process. Since it must communicate to people of different backgrounds, detailed design must have a "universal" and common language, which allows to understand the document without the support of an oral explanation.
For this reason, each entry must contain the dimensioning and the description of all the elements. It is important to note that each entry has a more or less circumscribed topic: in a good drawing, dimensions and descriptions relate solely to that topic.
Another key element to a good understanding of the drawings are the schematical references that link drawings together. As a story, in fact, it develops from the general to the particular and accordingly from the greater scale to the detailed one: the passage from a plan to a section, from a general to a particular table must always be reported.

Detailed drawings which make up the architectural project

A general arrangement plan is the first key to understanding the drawings. If the project is large can be divided into lots and the general plan will bring the same subdivision of lots, each of which will have its own specific plant. In this phase the representation scale ranges from 1:500 to 1:100.
The plans make possible to give different directions and often they are produced in different sets that contain specific information or are the keys to other drawings. As an example, plans of different kinds may be developed as follows:

  • General arrangement plans
  • Floor plans
  • Ceilings plans
  • Plans referring to details
  • Plans referring to typical elements

These drawings will be in general developed to a scale normally between 1:50 and 1:200.

For premises with peculiar connotations, more detailed drawings will be developed. It is understood that, if I'm representing a big empty room, the detailed information will already be in the general drawings; instead if I'm dealing with a small and very "designed" one, such as a bathroom, I'll detail it on a larger scale, 1:50 to 1:10.

Then Iíll pass to more accurate details describing real objects, components, and special technical solutions, from 1:20 to 1:1.
I report below a detail of this type, a hand-drawn detailed design developed 18 years ago.

il disegno esecutivo realizzato da Collettivo 4 Outsourcing

Finally I will compile a series of charts describing all the repetitive elements of the project, such as:

  • Doors, windows, glazings;
  • Walls and partitions;
  • Balustrades and railings;
  • Etc.

Detailed design and CAD

The detailed design is almost always developed with CAD and its transmission occurs directly by exchange of files, especially during the design phase for midterm, or on paper in the delivery phase of the project.

Collettivo 4 Outsourcing "plans" shop drawings so that:

  • The drawings can be presented in one or more tables, linked together through graphic references;
  • The revision and updating are handled with ease and safety by modifying the smallest number of files.

The final drawing should in fact be composed of a small number of files, interfaced through a clever use of "blocks" and especially "xrefs". Only with this kind of planning all revisions and updates made both in the planning phase and as a result of its approval by the client and during the construction phase will be possible.
Furthermore in this way the detailed design will interface effectively with other drawings that make up the executive project, be them calculations, estimates or security plans. All this while waiting for the interoperability of software to become a reality in Italy as well, and for the different data of a building (from the design phase to the life of the finished structure) to be managed by a BIM.