Preliminary project in Switzerland: content, costs, process and quality criteria
- Simon Käslin
- Jan 5
- 16 min read
Updated: 51 minutes ago
Summary
In Switzerland, the preliminary project is the phase in which an idea becomes a robust building concept. It is the phase in which the building is developed conceptually to the point where building law, use, volume and costs fit together as a basis for decision-making. For many clients it is also the first moment in which the project really becomes tangible: volume, access, outdoor spaces, windows and rooms are visible and open to discussion for the first time. It is precisely in this phase that raumwert plus often provides support with second opinions, checks of the basic information and a sober assessment of variants, cost assumptions and risks. In this phase variants are examined, areas and volumes are checked for plausibility, risks are made visible and an initial cost estimate (often structured according to the Swiss cost classification BKP/eBKP) is drawn up. Many later problems arise because decisions are taken too early in the preliminary project, or because the checks are not carried out consistently enough.
Table of contents
Why does the project become tangible for many clients for the first time in the preliminary project?
What questions must a good preliminary project in Switzerland answer?
What documents do you need for a preliminary project in Switzerland?
What results should be available after the preliminary project?
What does a preliminary project for a detached house cost in Switzerland?
What does a preliminary project for an apartment building cost in Switzerland?
How accurate is the cost estimate in the preliminary project?
Which typical mistakes happen most often in the preliminary project?
How can you tell as a layperson whether a preliminary project is good?
How many variants should be examined in the preliminary project?
What is different for a detached house compared with an apartment building?
Three practical examples: typical situations and concrete decisions
What role do SIA 112 and SIA 102 play in the preliminary design phase?
What is the difference between a preliminary project and a building application?
What happens after the preliminary project up to the building application?
Questions about your preliminary project?
What is clarified now does not have to be replanned later. Discuss your questions in a free initial consultation.
1. What is a preliminary project?
A preliminary project in Switzerland is the planning phase in which a building project first becomes concrete enough for the central decisions to be taken properly. Many Swiss planning processes follow the SIA phases (SIA 112). In many Swiss projects the preliminary project corresponds to phase 31 under SIA 112. It sits within the project planning stage, before the documents for the building application are finalised.
The preliminary project is not about planning every detail. It is about developing the concept to the point where building law, use, volume, site servicing, the basic technical strategy and the cost logic fit together. For clients this is the point at which an idea becomes a project that can be checked, explained and financed.
Typical contents of a preliminary project are:
Room programme or written brief as a clear basis
Design drawings (floor plans, sections, elevations) at a sensible level of detail
Comparison of variants (at least one genuine alternative, often several)
Review under building law (zoning logic, dimensions, setbacks, parking, conditions)
Initial technical decisions in principle (e.g. plant room, service shafts, heating system in outline)
Structured cost estimate with assumptions and ranges (BKP/eBKP)
raumwert plus is often brought in during this phase when an independent assessment is wanted, for example with tight budgets, with complex plots, or when variants exist but are hard to compare.
2. Why does the project become tangible for many clients for the first time in the preliminary project?
Before the preliminary project there are often images, wishes, examples from the internet and a rough budget. The preliminary project is the first stage that produces a clean building volume and a floor plan logic that can be understood spatially. That is an important step for clients, because from this point on decisions are no longer abstract but visible.
In the preliminary design you typically see for the first time how the house sits on the plot, how the access works, which outdoor spaces are created and how the rooms relate to each other. This makes it possible to judge variants realistically instead of deciding on gut feeling alone. With detached houses in particular this is often the moment when everyday use can be thought through at all, for example routes, storage space, light, privacy and the connection to the outside.
Once the project is tangible, clear criteria are needed so that a first impression becomes a robust decision.
3. Do you need a preliminary project, or is a sketch enough?
A sketch can help to collect ideas, but it does not replace a preliminary project when the chances of approval and the financing have to be examined seriously. In Switzerland, building law, setbacks, heights, parking and conditions are often the limiting factor, not creativity. Without a preliminary project these limits often only become visible later, and then with more cost and more lost time.
A preliminary project is particularly important when the plot is demanding (slope, site servicing, proximity to boundaries, noise), when the budget is tight or when letting is planned. For apartment buildings it is nearly always central, because area efficiency, site servicing, parking, building services and approval risks have to be considered together.
In this situation raumwert plus typically acts as a neutral quality filter, before time and budget flow unnecessarily in one direction: checking assumptions, making variants comparable, making risks visible and putting decisions on a more robust footing.
4. When is the best time to start a preliminary project?
The best time has come once the plot and the intended use are clear and a realistic budget exists, but before large planning costs arise and before you commit emotionally to one solution. If a land purchase is imminent, an early start is particularly worthwhile so that you do not buy on assumptions.
It is often too late once a date for the building application has already been set and there is hardly any room for manoeuvre. Variants are then often only examined superficially, or not at all. Another typical late mistake is to develop one solution down to the last detail even though the basics (easements, building lines, site servicing) have not yet been properly clarified.
If you treat the preliminary project as an independent decision block, the rest of the process usually becomes calmer.
5. What questions must a good preliminary project in Switzerland answer?
A good preliminary project is useful when it answers questions in such a way that you understand the consequences and can stand behind them. Four levels have to fit together: law, function, cost and risk. If one level is missing, the next step becomes uncertain.
A preliminary project typically has to clarify:
Does the project fit the plot under building law (zone, dimensions, setbacks, parking, conditions)?
Does the use work in everyday life (detached house) or in the market (apartment building, letting potential, ancillary rooms)?
What does the project cost within a realistic range, and which assumptions lie behind that figure?
Which risks and open points exist (easements, ground conditions, objections, building services, programme)?
A common mistake is that a fine design is produced but the decision logic behind it is not documented. Later the justification for choosing exactly this solution is missing.
6. What documents do you need for a preliminary project in Switzerland?
Many problems arise not because of poor planning but because of missing basic information. In Switzerland in particular, easements, building lines or site servicing questions can strongly influence a project. The earlier these topics are properly on the table, the fewer redesigns follow.
Typically required documents are:
Land register extract and easements (rights of way, utility easements, building restrictions)
Building and zoning regulations and the zoning plan of the municipality
Site plan and official survey, spot levels, relevant setbacks (e.g. building lines, watercourses, forest)
Site servicing information (access road, utility mains, sewer)
For conversions: as-built drawings and information on the existing fabric
Budget framework and objectives for use (own use, letting, secondary flat, future flexibility)
If these basics are incomplete, designs are often only apparently concrete. A typical contribution from raumwert plus here is the structured review of land register and easements, the building law framework and the site servicing, so that the design work builds on solid foundations.
7. How does a preliminary project work in practice?
A good preliminary project is a managed process. It starts with clarifying the objectives and ends with a decision. In between it needs variants, comparisons and a clean reconciliation with building law and costs. If this sequence is not led consciously, unstructured iterations often follow, along with the feeling that planning is happening but certainty is not increasing.
Typically the preliminary project starts by clarifying priorities, budget, timeframe and use. Next comes a review under building law and a check of the basic information, so that no design time flows into directions that would not be approved anyway. After that, two or three genuine variants are usually developed. Genuine means not merely cosmetic, but relevant in functional, spatial or economic terms. These variants are then compared and narrowed down against defined criteria.
At the end the preferred variant is consolidated: drawings become clearer, area figures become robust, the technical decisions in principle are checked for plausibility, and the cost estimate is built up in a structured way. A good preliminary project does not end with drawings, but with a comprehensible decision.
8. What results should be available after the preliminary project?
After the preliminary project the next phase should no longer consist of searching, but of working things out. As the client you should have the essential basics available in an understandable form. That matters not only technically but also practically: many clients can only really judge whether they recognise themselves in this solution once they have these results.
After the preliminary project the following should normally be available:
Drawings (floor plans, sections, elevations) as a basis for decisions
Area and volume figures, separated in a comprehensible way
Review under building law (which rules apply, where the limits are)
Variant decision with justification
Cost estimate with ranges, assumptions and a reserve logic
List of open points and risks
If these elements are missing, the step to the building application often becomes unnecessarily unsettled. If individual points are missing or unclear, a short second opinion from raumwert plus often helps to close assumptions, key figures and open risks before the building application starts.
9. What does a preliminary project for a detached house cost in Switzerland?
The costs vary considerably. Ranges are more useful than fixed figures, because plot, complexity, the number of variants and the desired depth differ. As a guide, a preliminary project in Switzerland for a detached house often lies between roughly CHF 10,000 and 60,000. With simple starting positions and clear parameters it tends towards the lower end; with a sloping site, complex building law or several variants it tends to be higher.
What matters is not only the amount but what you get in return: a preliminary project is economical when it enables sound decisions and reduces later correction loops. A very cheap preliminary project can become expensive if it does not properly reflect building law, costs or risks and much has to be changed again later.
10. What does a preliminary project for an apartment building cost in Switzerland?
For apartment buildings the ranges are wider. Roughly speaking, depending on size and complexity, you can reckon with about CHF 20,000 to 180,000 and more. The effort is higher because topics such as parking, site servicing, fire safety, area efficiency and marketability have to be solved across several flats. A preliminary project for an apartment building therefore lies well above one for a detached house, depending on the project.
A decisive point is whether variants are really costed and examined in a comparable way. With apartment buildings in particular, small changes to the access, ancillary rooms or flat layouts often act several times over and have a large effect on costs, letting potential and yield. raumwert plus is frequently brought into preliminary projects for apartment buildings exactly where this effect needs to be made visible early.
11. How accurate is the cost estimate in the preliminary project?
A preliminary project cost estimate is an estimate, not a quotation. It should be understood as a range, because many details are not yet fixed and market prices fluctuate. The clearer the standard, the volume and the technical decisions in principle are, the more robust it becomes. What is decisive is that assumptions are transparent and cost drivers are clearly named.
As a client it is worth paying attention to the structure: an estimate to BKP/eBKP with plausible assumptions is usually a far better basis for decisions than a single figure without explanation.
12. Which cost drivers are set in the preliminary project?
Many clients believe that construction costs are mainly a question of the tenders. In practice, large parts of the costs are set in the concept. The preliminary project is therefore the phase in which the cost levers are visible and can be steered. Anyone who decides properly here has less to correct later.
Typical cost drivers are building complexity (many corners, offsets, complicated roof shapes), basements (excavation, waterproofing, ground risks), large spans and glazed areas (structure, detailing effort), technical standards (heat pump, geothermal probe, comfort ventilation, PV integration), as well as site servicing and surroundings (access road, retaining walls, terrain modelling). With apartment buildings the parking solution is often a further large lever, as is the internal access (staircase, lift, service shafts).
Anyone who first reduces complexity in the preliminary project when budgets are tight often achieves more than someone who saves on the fit-out later. In practice raumwert plus is often deployed where cost drivers not only have to be named but allocated concretely within the concept and weighed properly against each other across variants.
13. Which typical mistakes happen most often in the preliminary project?
The most common mistakes are not spectacular, but very expensive. A classic is fixing on one design early without genuine alternatives. Another mistake is missing basic information: easements, building lines or site servicing details surface late and force redesigns. Very common too is a cost estimate without clear assumptions, so that decisions rest on unclear figures.
With a detached house a typical mistake is weak area logic: a lot of circulation area, little storage space, an unclear plant room and laundry, impractical sequences. With an apartment building a classic is that floor plans look clean but are weak in letting, because furnishing, storage space, kitchen position, ancillary rooms or balcony quality do not work.
raumwert plus is often brought in exactly when this uncertainty is noticeable: nothing looks wrong, but nothing is robust either. In this situation an additional idea usually does not help; what helps is a clear check of the assumptions.
14. How can you tell as a layperson whether a preliminary project is good?
As a client you do not have to know the standards by heart. Quality can be recognised as a layperson too, if you pay attention to structure, transparency and readiness for a decision. A good preliminary project first explains which rules and assumptions apply, and then shows how the design follows from them. It names risks openly instead of hiding them, and it makes variants genuinely comparable.
Practical layperson checks are, for example:
Can you explain why this variant was chosen (not just because you like it better)?
Are areas and ancillary rooms plausible (storage space, plant, laundry, bicycles and prams in apartment buildings)?
Are daylight, orientation and the scope for furnishing comprehensible?
Are costs shown as a range with assumptions, and is there a reserve logic?
If you have less uncertainty after the preliminary project than before, that is a strong sign of quality. If you only see drawings but no clear decision logic, substance is often missing.
15. How many variants should be examined in the preliminary project?
In practice two or three genuine variants are usually enough. More variants often bring not more quality but more confusion. What is decisive is that variants rest on the same assumptions and are assessed against the same criteria. A clean comparison of variants uses identical key figures (areas, volume, cost range) and assesses building law, function, risk and cost.
Typical mistakes are sham comparisons: variant B is cheaper because important items are missing, or variant A is better because building law and parking were not examined to the same depth. If variants are not examined equally, the decision is not robust.
16. What is different for a detached house compared with an apartment building?
With a detached house, everyday quality of life is at the forefront. The preliminary project has to make sure that use, sequences and flexibility work, and that standard and budget fit together. Topics such as storage space, building services, outdoor space and future viability (home office, ageing) are often decisive.
With an apartment building a second logic is added: economic viability and letting potential. Here area efficiency (usable area versus circulation area), the marketability of the layouts, clear ancillary room concepts, internal access and technical systems count. Fire safety and parking are more often limiting than with a detached house. Small conceptual mistakes act in multiplied form in an apartment building, because they affect several flats at the same time.
17. Three practical examples: typical situations and concrete decisions
Practical example 1: detached house on a slope and the basement question
The preliminary project often shows that a basement on a slope ties up a large part of the budget. Excavation, waterproofing, drainage and retaining walls are not only expensive but also carry risk. A robust decision only emerges when the added value (usable area, building services, storage) is set against cost and risk.
A sensible next step is often to examine a genuine alternative, for example a partial basement or a split level. If these variants are not examined in the preliminary project, the basement is simply set later, even though it dominates the project financially.
Practical example 2: detached house with a generous floor plan but poor area productivity
A floor plan looks high quality but has over wide corridors, unclear storage solutions and unnecessarily large circulation areas. In the preliminary project this can be made visible by separating and assessing areas cleanly: what is really usable, and what is only a route?
Often the same living quality can be achieved with less area through small shifts. That is a direct cost lever, without having to save on the fit-out standard.
Practical example 3: apartment building with good architecture but weak letting potential
A design for an apartment building can look clean and still be weak in letting if kitchens are dark, storage rooms are missing, rooms are hard to furnish or balconies exist only formally. The preliminary project is the right moment to test floor plans against everyday use and the market.
Small changes to doors, service shafts, ancillary rooms or flat sizes can have a large effect on letting potential and yield later.
raumwert plus is often deployed on questions like these in order to make area logic, cost levers and risks visible together at an early stage.
18. What role do SIA 112 and SIA 102 play in the preliminary design phase?
In Switzerland many practices structure services and phases along SIA 112. SIA 102 is frequently used as a reference for service descriptions and fees. For clients this creates comparability and clarity, but it does not replace substantive quality. In practice it helps if the services and results are described properly for each phase, so that you know what you may expect in the preliminary design phase.
19. What is the difference between a preliminary project and a building application?
In the preliminary project the concept is developed and decided. It supplies the basis for the decision: which variant, which area logic, which cost assumptions, which risks. The step from the preliminary project to the building application is then the formal one, in which the project is worked out so that it can be submitted to the municipality and reviewed. A typical form of support from raumwert plus is to check once more before the building application whether the decisive assumptions (areas, standard, parking, risks) are properly documented and coherent in the preliminary project.
Preliminary project versus building application:
Topic | Preliminary project | Building application |
Objective | Find a solution and decide | Submit the solution formally and obtain approval |
Focus | Variants, feasibility, cost ranges, risks | Drawings and proofs complete, compliant with the rules, ready for submission |
Result | Basis for the decision (why this solution) | Submission documents for the municipality and the procedure |
Risk | Incorrect assumptions, unclear basics | Conditions, objections, formal queries |
If the preliminary project is weak, the building application becomes unsettled, because basics are suddenly missing or large topics only become visible then. A good preliminary project makes the building application more predictable, because the critical decisions have already been taken consciously.
20. What happens after the preliminary project up to the building application?
After the preliminary project comes the working out of the construction project for the building application. Drawings are detailed, proofs are prepared, specialist planning is deepened, and the documents are prepared so that the municipality can review them. The cleaner the preliminary project is, the calmer and more efficient this step runs. A weak preliminary project often leads to correction loops, because topics suddenly appear in the approval procedure that could have been clarified in the preliminary project.
21. Frequently asked questions about the preliminary project in house construction
Which SIA phase does the preliminary project correspond to? In many Swiss projects the preliminary project corresponds to phase 31 under SIA 112. It therefore sits within the project planning stage, before the documents for the building application are finalised. SIA 102 is frequently used as a reference for service descriptions and fees; it creates comparability but does not replace substantive quality.
Which basic documents have to be available at the start? Typically you need a land register extract and the easements, the building and zoning regulations together with the zoning plan of the municipality, a site plan and official survey with spot levels and relevant setbacks, as well as site servicing information on the access road, utility mains and sewer. For a conversion, as-built drawings and information on the existing fabric are added, plus the budget framework and the objectives for use. If these basics are incomplete, designs are often only apparently concrete.
What costs should you reckon with for a preliminary project? For a detached house a preliminary project in Switzerland often lies between roughly CHF 10,000 and 60,000, tending lower with simple starting positions and higher with a sloping site or complex building law. For apartment buildings you can reckon with about CHF 20,000 to 180,000 and more, depending on size and complexity. The higher effort comes from topics such as parking, site servicing, fire safety, area efficiency and marketability.
How many design variants are needed for a decision to be robust? In practice two or three genuine variants are usually enough; more often bring not more quality but more confusion. What is decisive is that all variants rest on the same assumptions and are assessed against the same criteria, that is with identical key figures for areas, volume and cost range. If variants are not examined to the same depth, the decision is not robust.
What should a client have in hand at the end? As a rule, drawings with floor plans, sections and elevations should be available as a basis for decisions, together with area and volume figures separated in a comprehensible way and a review under building law. This is complemented by the variant decision with justification, a cost estimate with ranges, assumptions and a reserve logic, and a list of open points and risks. If these elements are missing, the step to the building application often becomes unnecessarily unsettled.
Which decisions in the concept influence the construction costs most? Typical cost drivers are building complexity with many corners, offsets and complicated roof shapes, basements with excavation, waterproofing and ground risks, large spans and glazed areas, technical standards such as heat pump, geothermal probe, comfort ventilation and PV integration, as well as site servicing and surroundings. With an apartment building, the parking solution and the internal access with staircase, lift and service shafts are added as large levers. Anyone who first reduces complexity when budgets are tight often achieves more than someone who saves on the fit-out later.
Questions about your preliminary project?
What is clarified now does not have to be replanned later. Discuss your questions in a free initial consultation.
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