Architect contract in Switzerland: SIA 102 fees explained
- Simon Käslin
- Jul 1
- 7 min read
Updated: 6 hours ago
Summary
For many private clients, the architect contract in Switzerland and the fee under SIA 102 are a black box. They understand what an architect does, but not how the fee is made up and why the different methods produce such varying amounts.
SIA 102 is the central SIA regulation for the services and fees of architects in Switzerland. It provides for several calculation methods, defines service phases and allows for special surcharges on conversion projects.
Anyone who understands the basics can compare quotes, recognise fair contracts and avoid unpleasant surprises. On request, raumwert plus reviews architect's contracts and fee quotes as an independent second opinion.
Table of contents
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1. What does the architect contract in Switzerland regulate?
The architect's contract sets out which services the architect provides, in which phases, for what fee and with what responsibility. It is the basis of the collaboration and should clearly define what is included and what is not.
An important point from practice: many architects do not use the official SIA contract form but their own contract, which refers to SIA 102. That is entirely normal and legitimate.
What matters is not the form itself, but that the services, the fee method and the responsibilities are clearly set out and that SIA 102 is referenced as the basis in a comprehensible way.
2. What is SIA 102?
SIA 102 is the regulation issued by the Swiss Society of Engineers and Architects (SIA) for the services and fees of architects. It is not prescribed by law, but it is the established standard in Switzerland.
It creates comparability by defining service phases, sub-services and calculation methods.
Further information on the regulation is available directly from the SIA. For clients, what matters most is that SIA 102 creates a common language: if both quotes are based on it, they can be compared.
3. How is the architect's fee calculated under SIA 102?
SIA 102 provides for several methods. The two most important ones for private clients are the outdated calculation based on the construction costs to be spent and the modern calculation based on actual time spent. Lump sum fees are also possible and are usually derived from one of these methods. A neutral aid for a rough classification is the value app of ETH Zurich (value-app.ethz.ch), which makes the fee transparent according to SIA logic. Construction costs can still be used as an approximate value for the fee calculation.
Project | Fee (% of construction costs) | Example at CHF 800,000 |
New single-family house (full mandate) | approx. 10 to 15% | approx. CHF 80,000 to 120,000 |
Conversion / renovation | approx. 12 to 18% (with conversion surcharge) | approx. CHF 96,000 to 144,000 |
Partial mandate (planning and building application only) | approx. 5 to 8% | approx. CHF 40,000 to 64,000 |
Guideline values under SIA 102. The effective rate depends on the degree of difficulty, the scope of services and the degression.
Which method makes sense depends on the project phase. In early phases that are still unclear, time spent is often fairer because the scope is hard to estimate. As soon as the project is clearly defined, a lump sum fee can be set cleanly.
The fee is then split across the individual service phases in order to determine which phase earns which share:
Phase | Sub-services |
Preliminary design | 9% |
Building project with building application | 21% |
Permit procedure | 2% |
Tendering, comparison of quotes, award proposal | 18% |
Detailed design | 16% |
Execution / realisation with construction management | 32% |
Commissioning, completion | 2% |
4. What does remuneration based on construction costs mean?
With this method, the fee is derived from the chargeable construction costs, multiplied by factors for the degree of difficulty and the scope of services. One important detail is the degression: the percentage fee rate falls as construction costs rise, because larger projects do not cause proportionally more work. This type of calculation is outdated, but architects still like to use it.
For clients, this means that the fee is not simply a fixed percentage of the construction costs but the result of several factors. That is precisely why quotes without an explanation of these factors are hard to assess.
5. What does remuneration based on time spent mean?
With remuneration based on time spent, the work actually performed is charged at an hourly rate. This method is transparent and fair when the scope is unclear, for example at the start of a project or for advisory services.
In early phases in particular, or in phases that are hard to estimate, remuneration based on time spent is often the cleanest solution for both sides.
If it is still unclear how much work will be involved, for example during clarifications, variant studies or at the start of a conversion, a lump sum avoids either excessive risk premiums or later renegotiations.
Time-based billing becomes fair and transparent when it is combined with an estimate of hours: the architect estimates the expected effort in advance but bills the time actually spent. This gives the client a point of reference without creating an artificial lump sum that serves no one.
6. What SIA service phases are there?
SIA 102 structures the architect's services into phases that follow the project phases of SIA 112. In simplified terms, they run from the preliminary studies through the preliminary design and the building project, the building application and the tendering process, to realisation and completion.
This logic of phases is useful because it shows which service is provided when. What a good preliminary design looks like is covered in the article Preliminary project for a house build in Switzerland, and the formal building application in the article Building application and building permit.
7. What is different in a conversion (conversion surcharge)?
Conversion projects involve more effort than new builds because the existing building carries uncertainties and the planning has to connect to what is already there. SIA 102 takes this into account through a conversion surcharge that reflects the higher effort. As a result, the effective fee for conversions is often noticeably higher than for comparable new-build costs.
This is not an arbitrary mark-up; it reflects real additional work. Anyone planning a conversion should budget for it. Whether a conversion is worthwhile at all is covered in the article Renovate or demolish, and adding a storey in the article Adding a storey to a single-family house.
8. What is a full mandate and what is a partial mandate?
With a full mandate, the architect accompanies the project through all phases, from the first idea to the handover of the keys. With a partial mandate, only individual phases or services are commissioned, for example planning and the building application only, without construction management.
Both models make sense, depending on your needs. What matters is that the contract states clearly which phases and services are included. Gaps between partial mandates are a frequent source of misunderstandings and additional costs.
9. What should you look out for in the contract?
A good architect's contract is understandable and complete. Look out for the essential points, even without legal knowledge.
Which service phases and sub-services are included?
Which calculation method applies and how is it derived?
Which degree of difficulty and which factors are applied?
How are additional services and changes charged?
How are liability, insurance and termination regulated?
If these points are clear, the contract is usually sound. If a lot remains open, a closer review is worthwhile.
10. Which mistakes happen most often?
The most common mistakes arise from a lack of transparency. Clients compare quotes that are not comparable because the scope of services or the factors are defined differently. A supposedly cheap quote then contains less service.
Another mistake is to look only at the percentage instead of the services included. The cheapest fee is not the most economical one if important phases are missing or have to be commissioned later at a high price.
11. Three practical examples
Practical example 1: Two quotes, seemingly identical
Two architectural firms quoted similar percentages. The review showed that one quote did not include construction management. In reality it was considerably more expensive than it appeared.
Practical example 2: The underestimated conversion surcharge
A client compared the fee for his conversion with guideline values for new builds and felt it was high. Explaining the conversion surcharge made the additional work understandable and the fee fair.
Practical example 3: A clean start to the phases
One client deliberately started the early phase with a partial mandate based on time spent and agreed a lump sum as soon as the scope was clear. This kept the cost risk limited during the uncertain phase.
12. Frequently asked questions about architect's fees
How is the architect's fee calculated?
In Switzerland, usually under SIA 102, either from the chargeable construction costs with factors for difficulty and scope of services, or based on actual time spent. Lump sum fees can also be derived from these methods.
How much does an architect cost?
That depends on the construction costs, the degree of difficulty and the scope of services. Because of the degression, the percentage rate falls as construction costs rise. A fixed percentage on its own therefore says very little.
Do architects need the official SIA contract?
No. Many architects use their own contract, which refers to SIA 102. That is normal and legitimate. What matters is that the services, the fee method and the responsibilities are clearly set out.
What is the conversion surcharge?
A surcharge under SIA 102 that reflects the higher effort involved in conversions. Because the existing building carries more uncertainty, the fee for conversions is often higher than for comparable new-build costs.
When does billing based on time spent make sense?
In early phases or phases that are hard to estimate, when the scope is unclear. It becomes fair with an estimate of hours: the architect estimates the effort in advance and bills the time actually spent.
13. When a second opinion on the contract is worthwhile
An architect's contract ties you in for years and involves considerable sums. An independent assessment before you sign is inexpensive in relation to that and creates certainty. It shows whether the services, the fee and the factors are consistent and whether the quote is comparable with others.
Unsure about your fee quote?
An independent assessment provides clarity before you sign.
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