What is a preliminary design?
A preliminary design (Dutch: voorontwerp, also voorlopig ontwerp or VO) is the design phase in which the architect develops the ideas from the sketch design into a coherent plan. In the Dutch building process, the preliminary design follows the brief (programma van eisen) and the sketch design (SO) and comes before the final design (DO). After that come the technical design and the specification.
What does a preliminary design contain?
- floor plans, sections and elevations to scale;
- a site plan showing the position on the plot;
- the main outline of the structure and building services;
- reference images, 3D images or a scale model;
- a first cost estimate.
The preliminary design must fit within the client’s brief: rooms, floor areas, budget and quality requirements.
In practice: getting more out of the VO phase
- Check against the omgevingsplan. In the Netherlands, check at this stage whether the plan fits within the municipality’s rules (the omgevingsplan), such as building height, built-up area and distances to the plot boundary.
- Hold preliminary consultation. Many Dutch municipalities offer the option of submitting a preliminary design in advance, including to the welstand (design review) or heritage committee. This prevents you from having to overhaul the design later.
- Involve the structural engineer and building services installer early. Service shafts, duct routes, load-bearing walls and spans often determine the floor plan.
- Record decisions. Have every change and every decision recorded in minutes. Changes are still cheap now; in the construction phase they cost much more.
- Check the cost estimate critically. This is an outline estimate. Keep a contingency allowance.
Difference from the sketch design and final design
In the sketch design, variants are explored. In the preliminary design, one direction is chosen and developed. In the final design, dimensions, materials and detailing are fixed to the point where the application for an environmental permit (omgevingsvergunning) and the technical design can begin.
| Sketch design (SO) | Variants are explored. |
|---|---|
| Preliminary design (VO) | One direction is chosen and developed. |
| Final design (DO) | Dimensions, materials and detailing are fixed, so the environmental permit application and the technical design can begin. |
Related terms
- Sketch design
- Final design
- Brief (programma van eisen)
- Architect
- Welstand committee
- Environmental permit (omgevingsvergunning)
- Specification
Want to learn more about construction terms? Visit our knowledge base at fredsdiyplans.com.