Last edited 30 Sep 2020

Common mistakes on building drawings

Many types of drawing can be used during the design and construction of buildings, often prepared by different disciplines or teams, working separately from one another. There are several common mistakes that can be made when producing or interpreting drawings that can lead to costly delays and avoidable remedial work.

A simple but common mistake is drawings not being complete. This can be a particular problem where designers do not have the necessary experience, supervision, quality systems or time to produce the drawings required. Incomplete drawings can lead to requests for information and change orders when the work starts on site.

Designers may also omit some detailing during the design process, such as window details or roof construction details, intending to complete them later, and will instead provide notes about what that portion of the construction should consist of. This can become a problem If they do not return to update the drawings before construction begins.

Drawings may not be coordinated, in particular if they are prepared by different teams, for example, the information on structural drawings may not be consistent with ductwork drawings. This can result in 'clashes', such as ventilation ducts running through structural beams (a hard clash), or insufficient space for installation works or access for maintenance (a soft clash). To try and void this problem, the design team should regularly review all up-to-date working drawings to ensure that they coordinate accurately.

Building information modelling (BIM) can help prevent clashes. Clash detection software can identify clashes between different disciplines' BIM data and generate clash reports. However, this should not be relied upon as a fail-safe check, and should not be used to justify poor design co-ordination processes. For more information see: Clash avoidance.

There may also be inconsistencies between drawn information and written information, such as schedules or specifications. It is important therefore that information is not duplicated between different types of document, but rather that one refers to the other. For example, a drawing may include notes referring to additional details in specification clauses.

In terms of personal drawing style, designers may have in-house habits that are not understood by other teams or disciplines. This can lead to misinterpretation and mistakes. It is important therefore that drawings adopt standard methods and procedures for preparation, symbols, hatching, annotation and so on. These should be agreed at the outset so that early drawings do not have to be corrected. This is particularly important when drawings are prepared using computer aided design (CAD) or BIM. BIM can involve the federation of information prepared by multiple teams to create a single model. If the information is not created consistently, incompatibilities can emerge that can be costly and time consuming to correct.

In terms of technical details, common mistakes include:

Incorrect or inconsistent scales being used across drawings.
Doors opening the wrong way or with insufficient opening space (i.e. opening into other doors, cabinets, windows, etc.).
Facilities located in impractical places.
Undersized, impractical or awkward spaces.
Poorly detailed junctions or abutments between different components or systems.
Incorrect symbols.
Inconsistent revision numbers.
Poor reproduction.
File exchange or conversion errors.
Software incompatibilities.
Un-buildable, or difficult to build elements.
Missing components.
Inconsistent information.
Illegible writing.
The use of acronyms that are not understood.
Notes that are not understood.