Understanding Section Drawings

Among the many views in a set of architectural plans, very few come close to a section drawing

Among the many views in a set of architectural plans, very few come close to a section drawing. While floor plans, elevations, and perspectives get most of the attention, sections play a vital role in telling a buildings whole story.

Without them, we would not be able to see and communicate how a buildings spaces and volumes connect and come together. In this article, we cover all the fundamentals of section drawing, as well as tips and resources to help improve your presentation.

What is a section drawing?

In short, a section drawing is a view that depicts a vertical plane cut through a portion of the project. These views are usually represented via annotated section lines and labels on the projects floor plans, showing the location of the cutting plane and direction of the view.

We provide a selection of these labels and fully annotated examples in our AutoCAD Template here.

Sections can be orthographic views, where the drawing is shown parallel and two-dimensionally, or perspective views with three-dimensional depth.

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What is its purpose?

Section drawings help provide a better understanding of the internal portions of a building, showing many key items that wouldn’t otherwise be visible in the other views.

They can show intricate details at various scales to enrich drawings with information and additional visual reference.

Clients look at sections to see the relationship and enclosures of the interior spaces. Consultants look at sections to aid in the accurate design of engineering components, and builders refer to sections during construction to make sure everything is built as planned.

Why are they important?

A clear set of section drawings are crucial for stakeholders to understand the inner workings of a building. They play a key role in connecting information from the elevations and exterior views to the floor plans and interior views.

Some of the most sophisticated buildings today are best characterized by their sections, because their true forms are often not seen from the exterior facades. Designs with complex and dynamic levels use creative section drawings to illustrate the ideas for their full appreciation.

What should a section show?

Sections can show the relationship between floors, walls, windows, ceilings, roofs, and other elements intersecting the cutting plane. They can also show how elements such as glass, concrete, and cladding are assembled together with seals, insulation, and termination details.

An effective section is one that illustrates information lacking from other views. For example, it might be difficult to see the floor slab thickness in an elevation, or the void spaces via a floor plan, but a section drawing can show both with ease.

Likewise, contour lines on site are a good indication of sloping land, but it can be strenuous trying to visualize the steepness without a visual guide on a section.

How to read a section

Imagine a slice of cake, showing the layers of frosting and filling from the base all the way up to the decorative elements on top. A section drawing is very similar, with the layers and stories on full display.

Whether it’s a full building section, or a small joinery detail, the principle remains the same.

For a typical building section, you’ll likely see a mixture of ground, structural elements, and architectural features. The first step to reading it is to find the section line on the floor plans. There you’ll be able to orient yourself with the location of the section in the building.

Once you analyze the areas intersected by the section line, you can refer to the elevation views to understand which elements of the exterior are being shown. After that, much of the section should start to make sense, and you’ll have a clear idea of the spaces and features in view.

Types of sections and section styles

Detail – A detail drawing refers to any isolated or enlarged view of a specific part or element, showing an additional level of detail and providing more complete descriptions of the components within it.

A detail section is often used to show how small pieces are put together. These are typically characterized by plenty of call-outs and labels, as well as a wide variety of line styles and hatch patterns to differentiate materials and masses.

Full – Full (or typical) sections have a cutting line that passes all the way through the building or object. They are useful for getting a complete, big picture look through the inside of a structure. These sections show a full slice of a building from top to bottom to provide an overview of the building envelope and the spaces in between.

Half – A half section, as the name implies, is a view wherein only half of the object has been cut, with the other half being shown as an elevation. This means that only a quarter of the object is being removed, with the rest of it left intact.

When represented on a floor plan, half sections have a section line that typically turns at a 90-degree angle from the midpoint, creating an opening that allows you to see both the interior and exterior in one view.

Site – Site sections are a way to cut the full site along with terrain and land elements to show the macro relationship of all structures in the development. This is most appropriate for complexes involving several buildings grouped together.

You will also see many site sections for projects on steep hillsides or along the beach. These views offer helpful visual guides for topography and land grading, such as cut and fill works and below-ground spaces.

Longitudinal – A longitudinal section is cut along the long axis of a structure. It is a full lengthwise section showing the structure in its entirety from top to bottom. Longitudinal sections are common in architectural plans as one of the main requirements for permits and construction.

Offset – An offset section involves a cutting plane that does not cut in a straight line. Instead, the line has many deviations as it cuts across the structure to include different objects in the same view. The deviations are generally done at right angles to show different depths in the section while maintaining the same view plane.

Perspective – Perspective sections are used primarily for presentation purposes to illustrate the ideas and communicate the design to the client. These section views depict three-dimensional depth beyond the cutting plane to show things like space, finishes, furniture, people, and light.

Broken – A broken section is a reference view with one or more parts omitted to show only the essential aspects of the drawing. Instead of isolating an area as a whole, broken out sections use break lines to represent continuation and omission.

This technique is ideal for detail views to reduce the overall size without compromising the content and information of the drawing. Walls and floors are commonly divided by break lines due to their length and continuity.

Poche – Poche is a style of section presentation that involves filling, hatching, or shading cut components to differentiate sliced members from projected faces. In a section, poche is most frequently used for floors, walls, and beams. Various hatch patterns and opacities can be used to make it easier to distinguish different materials, structural members, and finishes.

Shadowing – Shadowing is used as a section style to produce subtle gradients of light and dark on the inner walls of a section. This technique can be applied to more effectively explain how the sources of light, both natural and artificial, illuminate the interior spaces within a building.

Line – A line drawing is made of pure lines, without any color, shade, or shadows. Line sections can make drawings easier to measure on site, as bare lines are more precisely visible than solid colors or gradient shadows. Technical drawings for construction are often done as line drawings to retain as much information as possible.

Oblique – Oblique sections are made by cutting non-right-angle planes into the building or object. These section lines are drawn diagonally, or not along the horizontal or vertical planes of the project. Oblique sections are commonly used for round or radial designs to cover areas that weren’t sufficiently shown by the cross and longitudinal sections.

How do you draw a section?

There are different approaches to creating section drawings depending on what materials and programs you’re working with, but the overall process remains consistent. The below stages highlight the basics for creating a section from scratch, and these steps are applicable for both manual and digital drafting.

Make the section cut – The first step is deciding where to make the cut. This includes the placement of the section line, direction of the view, rooms to be intersected, and other important elements that you want to include in the drawing. Make sure the section line is consistently placed on all floor plans, as well as elevations if necessary.

Reference all relevant views – Reference the affected views to create the outline of the building, and prepare the drawing with the appropriate measurements and scale.

Draw the inner components – Add the interior walls, windows, doors, ceiling, hardware, and fixtures as needed. It is advisable to regularly cross-reference views to ensure accuracy and correctness.

Add necessary graphics – Once the main components have been drawn, you can add hatch patterns for cut walls, earth, gravel, wood grain, finishes, and insulation.

Add annotations – Annotations are a critical part of architectural sections. This is when you add important information with labels, callouts, tags, and dimensions.

Refine presentation – Whether the section is for construction use or presentation, it’s always important to make it clear and concise to ensure readability. For technical drawings, this can mean cleaning up the linework and adjusting the fonts for optimal legibility. For presentation, this can include adding color and other imagery to make it easier to understand.

Enhance your drafting skills with a course – To learn more about how to make section drawings, here are some helpful classes to guide you with detailed instructions and demonstrations:

How to improve your section drawings

Lineweights

Lineweights are different thicknesses for line presentation. They can be used to represent distance, foreground and background, significance, and detail.

In a section, major architectural elements can be shown in bold lines, while minor details such as wall patterns and vegetation can be shown with fine lines. Features in between, like doors and windows, can be shown with medium lines.

Lineweights help to add hierarchy and character, and in views such as detail sections, they can provide a clear distinction between different parts and materials.

Textures

Textures can provide a touch of realism to section drawings. They can be used for elements such as finishes, skies, roads, grass, and materials to make the view appear more life-like and appealing.

Textured sections are also easier to understand, as they relate directly to the material board without having to read finish tags or material callouts.

Light & shadow

Light and shadows can be added to sections to increase the depth and contrast between spaces. They can also help to convey the different ambiances from room to room.

Especially in designs with unique openings, light and shadow in the section can illustrate how windows, skylights, and voids bounce light into the interiors.

Cutouts

Cutouts can bring sections to life with entourage of people, plants, animals, and cars. These images can be used to populate spaces and make them feel more like the finished product. They can also be used to illustrate how spaces evolve during certain situations like events, gatherings, and special occasions.

Furniture

Furniture in a space provides a better idea of size and scale. It can make the section more presentable and more informative, and the users will be able to visualize their own furniture and lifestyles fitting in with the design.

Perspective

Perspective can be included in a section view to show depth and interiors. A perspective section can be drafted, modeled, or rendered.

These kinds of sections are favored for presentations because they pull more lines inward and expose more of the interior walls and ceilings, giving the impression of a truly cut building.

FAQs

What is sectioning in technical drawing?

Sectioning is the process of drawing an object cut open to show its internal configuration. It is done to look inside of an object, through strategic cutting planes that carry important information for construction or manufacturing.

The imaginary cuts reveal inside features for reference during implementation.

What is the difference between an elevation and a section?

Elevations and sections both show the vertical nature of a project, however the difference lies in that elevations are a view of the exterior facade, while sections are a slice through it showing the interior.

In order for a building to be constructed, both elevations and sections are needed to effectively communicate the design and structure as a whole.

What is the difference between a section and a detail?

A section refers to any drawing that portrays a vertical cut-through view of an object or building, while a detail drawing shows a specific area with additional levels of technicality, call-outs, labels, and information.

A detail drawing can be a plan, elevation, section, or any kind of other view, as long as it shows an enlarged or more descriptive aspect of a certain part or area.

What does Section AA mean?

The terms “section AA” refers to the first cut and view of the section line. Represented in plan through an annotation (often a circular bubble) at the end of the section line or via a drawing title block, the designation can be AA, A, A1, or other formats depending on your industry and the firm’s standards.

The section names then follow either an alphabetically or numerically formed order (BB, CC, DD and so on), or both, to denote the next section views for the project in question. They are also typically correlated with the sheet number and their order of presentation on the sheet.

What is a cross section in drawing?

A cross section is a view created by cutting through the short side of the building. The section plane lies perpendicular to a longitudinal section, and it’s used to show the inside of a building the same way. For square buildings, objects, and assemblies, a cross section can mean any section cut horizontally or vertically showing the inside.

Why should I learn section drawing?

You might be wondering why it’s still necessary to learn section drawing when 3D modeling and BIM programs can create section cuts in just a few clicks. Is it still practical to know how to draw sections, and is it an efficient use of your time?

The truth is, knowledge of drawing is a prerequisite to more complicated forms of architectural production. With a solid foundation of drafting principles, you can improve your overall presentation, recognize what graphic elements are missing, properly annotate and represent elements, and create refined sections in any medium.

archisoup.

Never search for a single CAD block ever again.

There is literally nothing worse than wasting valuable drawing time trying to find the “right” block, symbol, hatch or correct line weight. This template kit eliminates all of the guesswork.

In summary

Architectural design is a holistic process, and the inside of a building is just as important as its exteriors. Section drawings provide a unique look into the building while supplying essential information about the spaces and structure.

They can be used to make compelling presentations or detailed construction drawings, and they serve as valuable additions for all kinds of projects.

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