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Architecture section drawings

How to create architecture section drawings correctly and quickly with the help of a BIM software

Architecture section drawings are technical construction drawings essential for the representation of an existing work or project.

To create the section of a building with a CAD software, you need to start from the plan. Then you need to choose the vertical section and finally produce the  drawing. It is necessary to proceed similarly for each section.

By using a BIM software for architectural design, however, this process becomes automatic and leaves no room for errors.

Let’s see in detail what sections are and how to generate them with the help of a BIM software.

What are architecture section drawings?

In reference to architecture section drawings, the term section indicates an orthogonal projection of a building intersected with a vertical plane, that is, perpendicular to the horizon line.

This type of two-dimensional representation allows a control of the arrangement of spaces on the different floors, of the vertical connection elements (stairs, elevators, ramps, etc.), of the structures (floors, walls, pillars), of the differences in altitude, etc., showing the inside and outside of the building.

Conceptually, there is no difference between plan and section as both are orthogonal projections made on a section that is orthogonal to the object. Even a building plan is made of a section that is however obtained from a horizontal plane.

In general, the section plane is usually chosen in order to provide as much information as possible, useful for understanding the work. This should be appropriately indicated in the plan (conventionally drawn as a line made of  dots, dashes, arrows and letters).

To differentiate the sectioned parts from those not sectioned, as for plans, we use lines of different thickness (thicker for the sectioned parts, thinner for those not sectioned and dashed for the objects not visible but that we believe we must report in the drawing) and hatches (dashed or full).


section made with Edificius

Section made with Edificius

For the understanding of the drawing, it is always appropriate to also report the drawing scale chosen according to the level of detail that you want to reach with the drawing.

For example, you should use the scale:

  • 1:25,000, 1:50,000 for topographical representations;
  • 1:10,000, 1:5,000 for representations on a territorial/municipal scale;
  • 1:2,000, 1:1,000 for urban aggregates;
  • 1:500 for the transition from the urban scale to the architectural one;
  • 1:200 for the draft outline;
  • 1:100 for the architectural project;
  • 1:50 for the executive project;
  • 1:20, 1:10, 1:5 for details and construction details;
  • 1:1 for details that require full scale representation.

Even if you declare the scale, it is always a good idea to add the elevation on the drawings to add more information and to be immediately able to read the drawing correctly.

What are the types of sections used in architectural drawings?

There are three types of sections:

  • horizontal,
  • vertical,
  • oblique.

This distinction refers to the type of inclination of the plane with respect to the base of the dissected solid. The most used in architecture are horizontal sections (better known as plans) and the vertical ones (more commonly known as sections).

In addition, there are:

  • split sections, when the section line is not straight but at a certain point in its path it slides forward or backward by sectioning an area rather than the initial one. This type of section is widely used in the architectural field especially when you want to show with a single section more areas of the project;
  • longitudinal, when the section plane is parallel to the long side of the building;
  • transverse, when the section plane is parallel to the short side of the building
  • construction sections, when the level of detail is useful to represent the construction details of a building.

Sections are not only used in orthogonal projections but there are also axonometric or perspective sections.

Axonometric section created with Edificius

Axonometric section created with Edificius

How to draw a section: the benefits of using BIM software

To draw the section of a building it is necessary to imagine cutting it literally in half.  You have an imaginary plane and you remove a part and then draw with the method of orthogonal projections what is sectioned from the level and everything that is seen in projection. The purpose is to make its internal parts visible.

With a BIM software, it is no longer necessary to manually draw the sections. You simply need to indicate the section line, using a specific functionality of the software, to automatically generate the desired view. What you get is not a static drawing but a dynamic view connected to the 3D BIM model that updates automatically in case of changes.

This means that if I have already generated the sections but decide, for example, to change the height of the plasterboard false ceilings or the arrangement of the internal partitions, I do not have to redo all the all over again because when I modify the 3D model, all the views I have created get updated automatically and in real time.

Essentially, having the 3D model of a building available, it is possible to generate infinite sections (but also plans and elevations) and make continuous design changes without having to return to the drawings already made.

In addition, I can customize the style of the drawing (white to black, color, grayscale, etc.), the thickness of the lines, the screens, the representation of the furniture, etc., according to my needs and create working drawings, along with photorealistic renderings and 3D views.

Working Drawing generated with Edificius

Working Drawing generated with Edificius

All this is a great advantage for the professionals and leads to time savings and a significant cut on representation and design errors. In fact, having the possibility to generate in real time all the sections I need allows greater control and a more careful and critical verification of the project choices.

For more information on how to create construction documents from the 3D model, read the in-depth article.