Building Information Modelling (BIM) is a way of designing and managing a building using one shared digital model instead of separate 2D drawings. Each element in the model, such as a wall, beam, pipe or door, carries information: size, material, cost, supplier and more. Architects, engineers and contractors work from the same model, so clashes between structure and services show up on screen before they show up on site. Quantities come straight from the model, and the finished model can be used to run and maintain the building. In Tanzania BIM is used mostly on larger projects, but its benefits apply to any building with complicated services.
What is the difference between CAD and BIM?
| CAD | BIM |
|---|---|
| Lines and shapes on drawings | Objects with information (a "wall", not four lines) |
| Plans, sections and elevations drawn separately | All views come from one model and stay consistent |
| Changes made on each drawing | Change once, every view updates |
| Quantities measured by hand | Quantities taken from the model |
| Clashes found on site | Clashes found in the model |
How does BIM help a project?
Finding clashes before construction
The most immediate benefit. A drainage pipe running through a beam, a duct that will not fit above a ceiling, a column in the middle of a doorway: clash detection finds these in the model. On a building with air conditioning, sprinklers, lifts and complex wiring, it can save weeks of rework.
Better visualisation
Clients see the building in 3D before it is built, which leads to better decisions earlier. A board approving a school or office understands a 3D walk-through far better than a set of plans. See how to read house drawings for the traditional approach.
Quantities and cost
Because the model knows the size of every element, it can produce quantities for the Bill of Quantities. The QS still checks and prices them, but measurement is faster. Our post on estimating and BOQ software compares tools.
Planning and sequencing
Linking the model to the programme (sometimes called 4D) shows how the building goes up week by week. It helps plan cranes, deliveries and phasing on tight sites.
Running the building
After handover, an updated model holds information on equipment, finishes and services. Facility managers use it to plan maintenance. See construction handover documents.
What software is used?
Common BIM tools include Autodesk Revit, ArchiCAD, Tekla Structures for steel and concrete, and Navisworks for coordination and clash detection. Many firms combine them. Our guide to the best software for architects has more detail and rough prices.
Is BIM used in Tanzania?
Yes, increasingly. Larger architecture and engineering firms, international projects and some public projects use it. Smaller firms still mostly use 2D CAD. Barriers include software costs, training, and the need for every party to work in the same way. Projects get the most value when the architect, engineers and contractor all use the model, not just one of them.
When is BIM worth it?
| Project | Is BIM worth it? |
|---|---|
| Simple house | Usually not essential |
| Office, hotel, hospital, bank with complex services | Yes, especially for clash detection |
| Repeated designs (several schools, branch networks) | Yes, models can be reused |
| Large public or donor-funded projects | Often required |
| Renovations | Useful if the existing building is surveyed into a model |
What clients should ask for
- Which parts of the design will be modelled (architecture, structure, services)?
- Will clash detection be done before tender?
- Will quantities come from the model?
- Will you receive the final model at handover, and in what format?
How detailed is a BIM model?
Models are built up in levels of detail as the design develops, often described as LOD (level of development):
| Stage | What the model shows |
|---|---|
| Concept | Basic shapes, floors, approximate sizes |
| Developed design | Walls, slabs, columns, openings, main services routes |
| Construction drawings | Exact sizes, materials, fixings, services in detail |
| As-built | What was actually built, with equipment data |
You do not need the highest detail everywhere. Most projects model structure and services carefully where clashes are likely, such as plant rooms, ceilings and risers, and keep the rest simpler.
Starting with BIM as a small firm
For a small architecture or engineering practice, moving from CAD to BIM is a real change in how drawings are made. A gradual path works better:
- Train one or two people first and use BIM on one small, simple project.
- Build a library of standard objects: walls, doors, windows, columns, typical details.
- Agree with your engineers which software and file formats you will exchange (IFC is the open standard).
- Move to clash detection on larger projects once the team is comfortable.
Expect the first projects to take longer, not shorter. The time saving comes on later projects and when changes are made.
Frequently asked questions
Is BIM just 3D modelling?
No. 3D is part of it, but BIM is about the information in the model and how everyone shares it.
Does BIM make projects more expensive?
Design fees may be a little higher, but fewer clashes and less rework usually save more on complex buildings.
Do contractors need BIM?
Not always, but contractors who can read and use models coordinate better and price more accurately.
What is clash detection?
Software that checks a combined model for elements that occupy the same space, such as a pipe through a beam.
What is IFC?
Industry Foundation Classes, an open file format that lets different BIM programs exchange models.
Can BIM be used on renovation projects?
Yes. The existing building is surveyed, sometimes with laser scanning, and modelled first, then the new design is added. It helps find clashes between old structure and new services.
Does the client own the BIM model?
Only if the contract says so. Agree ownership, format and handover of the model when appointing the design team.
How long does it take to learn BIM software?
Basic modelling takes a few weeks of training and practice. Working confidently on full projects usually takes several months.
Planning a complex building?
Vika Construction works with design teams on buildings and fit-outs across Tanzania. Contact us to discuss your project.
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