A constructability review is a structured look at a design by the people who will build it: contractors, trade specialists, temporary works and logistics planners. The question is not "does it clash?" but "can we build it, in this order, with this access, these lifting limits and these tolerances, without making it unsafe or expensive?" A federated model makes the review faster and more concrete, because people can stand in the building before it exists.
At a glance
| Who leads | Usually the main contractor's design or construction manager, with the BIM coordinator running the model session |
| Who takes part | Site managers, trade contractors (steel, MEP, façade), temporary works, logistics, health and safety |
| When | At the end of each design stage, and before each work package is tendered or released for fabrication |
| Input | Federated model, outline programme, site constraints (access, crane positions, neighbours) |
| Output | A list of buildability issues with owners, recorded like coordination issues (often as BCF) |
| Differs from clash detection | Clash detection finds geometry that overlaps. Constructability finds things that fit on paper but can't be built well |
What a review looks at
| Area | Typical questions | Example finding |
|---|---|---|
| Sequence | Can each element be installed after the ones it depends on? | A riser's pipework can only be installed before the slab it passes through is poured |
| Access and space | Is there room to install, test and maintain? | Valves hidden above a fixed plasterboard ceiling with no access panel |
| Lifting and handling | Can it be delivered and lifted? What does each piece weigh? | A plant unit heavier than the tower crane can lift at that radius |
| Tolerances | Do adjoining trades' tolerances add up? | Curtain wall brackets need ±10 mm; the slab edge is built to ±25 mm |
| Temporary works | What holds it up or keeps people safe while it's built? | A transfer beam that needs propping through three floors below it |
| Repetition | Can it be standardised or prefabricated? | 14 bathroom layouts that could be 3 pod types |
| Safety | Work at height, confined spaces, hot works | Roof plant placed with no edge protection route |
How it runs with a model
- Prepare views for each area of concern: sections through risers, the crane radius drawn as a circle, a 4D sequence of the critical package.
- Walk the model with the trades, one zone at a time, using the questions above as a checklist.
- Record each finding as an issue with a viewpoint, owner and due date, the same way as coordination issues, so they are tracked to closure.
- Feed decisions back: into the design, the programme, the logistics plan or the method statement.
A practical tip: invite the trade foreman, not only the trade's design manager. The person who has installed the system a hundred times sees the problem in seconds.
Worked example
A hospital's plant room has two air-handling units. The model is clash-free. In the review, the mechanical contractor asks how the units get in: the only door is 1.2 m wide and each unit is 1.6 m. The options are delivering the units in sections (a different specification), leaving a builder's opening in the façade until the units are in (a programme and weather-tightness question) or moving the plant room. Found in a two-hour review, it is a decision; found on delivery day, it is a crane, a cut façade and a delay.
Common mistakes
- Treating a clash-free model as a buildable one.
- Reviewing only once, at the end of design, when changes are expensive.
- Inviting design consultants but not the people who will install the work.
- Keeping findings in meeting minutes instead of the issue log, so nobody tracks them.
Where to read more
Construction design and management regulations in many countries (in the UK, the CDM Regulations) require designers to eliminate or reduce foreseeable construction risks; constructability review is one of the main ways teams show they did. Professional bodies for construction management and value engineering publish guidance on buildability reviews.