Principal designer in a construction project – role, qualifications and cost 2026

Under Finland's Building Act (rakentamislaki, 751/2023), the principal designer (pääsuunnittelija) is responsible for the overall quality and coherence of a project's design. They make sure the architectural, structural, HVAC and electrical plans fit together without contradiction, and that every specialist designer is sufficiently qualified. Every permit-based project must have a named principal designer – without one, the application goes nowhere.

The reform also changed terminology: since 2025 the old building permit is a construction permit (rakentamislupa). The role stayed the same, but the classification of design tasks and competence assessment were made more precise.

What does a principal designer actually do?

• Assembles the design team and coordinates the plans into one consistent whole
• Ensures the plans meet the construction permit and local plan requirements
• Links the builder, the designers and municipal building control
• Assesses the plot's suitability: planning regulations, terrain, orientation
• Keeps the budget realistic by steering design choices from the start

The principal designer is not the responsible site manager. The site manager runs execution on site, with a typical input of 150–200 hours on a detached-house build. A permit-based project needs both.

How are responsibilities divided in a project?

The familiar logic holds: the builder carries the duty of care to ensure the project is designed and built to the regulations. The implementation liability of a "principal responsible implementer" in the original act was removed before the law came into force, so claims in older articles about new contractor liability rules are wrong. The principal designer and site manager are the builder's most important support, but the ultimate duty of care does not transfer to them.

Qualification requirements and demand classes in 2026

The Building Act divides design tasks into five demand classes: minor, conventional, demanding, highly demanding and exceptionally demanding – "highly demanding" is new in the reform. A typical detached or log house falls into the conventional or demanding class.

A principal designer must hold a degree in construction – architect, building architect, engineer or master builder – plus experience matching the task. Municipal building control assesses eligibility project by project. FISE certification is optional but makes competence easier to demonstrate.

What do a principal designer and design work cost in 2026?

The role is usually bought as part of an architectural or design contract, so look at the cost as a whole. Typical 2026 prices for a Finnish detached-house project:

• Full design package (architectural + structural + building services): €5,000–25,000, roughly 5–10% of the total budget
• Architectural design alone: €8,000–20,000, more for demanding projects
• Hourly rates: building designer €70–150/h, architect €100–200/h

The cheapest quote should not decide: a skilled designer pays for themselves by weeding out expensive mistakes before they reach the site.

The principal designer and the permit process in 2026

From 2026, construction permits have a guaranteed three-month processing time. The clock starts only from a complete application, so the designer's key permit-stage task is to assemble the application and attachments correctly in one go. A requirement to submit plans as a building information model or another machine-readable format came into force at the same time – confirm at contract stage that the designer has up-to-date tools. The principal designer also usually prepares or checks the cost estimate the bank requires for a construction loan.

When should you appoint a principal designer?

Ideally before you buy the plot. An experienced designer reads things from the plan extract and terrain that a layperson misses: how much building right is genuinely usable, how the building sits in the buildable area, and what foundation costs the soil implies. In a house-package delivery – log houses included – the supplier's designer can handle the building design, but responsibility for the whole rests with the named principal designer.

For a permit-exempt outbuilding, such as a sauna under 30 m², no formal principal designer is required – responsibility for compliance lies with the builder.

How to choose a principal designer

• Check the degree, experience with similar projects and FISE certification
• Ask for references from your building type
• Agree the scope in writing: the permit stage, design during construction, changes.
• Make sure the same person stays for the whole project

Allow one to six months for design and the permit before work begins. A designer chosen in a hurry – or changed mid-project – almost always shows up as a drawn-out permit process and rework on site.

• Under Finland's Building Act, the principal designer is responsible for the design as a whole and for the compatibility of all plans.
• Every permit-based project needs a named principal designer – without one, the construction permit does not move forward.
• Design tasks fall into five demand classes; a detached house is usually conventional or demanding.
• Qualifications: a higher-education construction degree and sufficient experience, assessed project by project by building control.
• A full design package typically costs €5,000–25,000 in 2026, or about 5–10% of the project budget.
• Appoint the principal designer before buying the plot – they assess the plan, building right and soil risks in advance.