What is the Swiss Building Cost Classification (BKP)?

Switzerland’s structure for construction costs

The Building Cost Classification BKP groups project costs by execution trade. Published as Swiss standard SN 506 500, it provides a consistent structure for cost estimates, procurement packages, commitments, cost control and final accounts.

Rather than allowing every participant to name cost headings differently, BKP assigns costs to a hierarchical classification. This makes budgets, awards and invoices easier to compare across a project.

What is BKP used for?

• structuring cost estimates and approved budgets
• organising procurement and work packages by trade
• assigning commitments and approved amounts consistently
• bringing quotations, contracts, variations and invoices together
• comparing budget, commitment, forecast and actual cost
• building comparable cost data across projects

A practical example

A project team holds a budget of CHF 420,000 for one trade group. Contracts worth CHF 365,000 have been awarded, approved variations add CHF 18,000 and the current forecast is CHF 401,000. Because each value uses the same BKP group, the team sees the trend before the final invoices arrive.

BKP and NPK answer different questions

BKP answers: where does this cost belong in the project structure? The Swiss NPK catalogue answers: which specific construction service is being described, priced and valued?

A bill of quantities may contain many NPK items that are mapped to one BKP cost group. A cost classification does not replace a detailed work description, and a work item does not replace the project-wide cost structure.

Trade-based and element-based cost plans

BKP follows execution trades. An element-based classification groups costs by components of the building. The element view is often useful during design, before procurement packages are fully defined. As delivery develops, the trade-based view becomes increasingly important. Any mapping between the two needs clear, consistent rules.

A dependable cost-control workflow

1. Define the applicable classification and edition at project outset.
2. Use the same allocation logic for budget, contracts, variations, forecasts and invoices.
3. Avoid unexplained catch-all groups or split them transparently.
4. Review coding during the project, not only at final account.
5. Document changes to the classification or mapping.
6. Compare actual cost through job costing against the same baseline.

Common errors

If the budget, contract and invoice use different allocation rules, a complete-looking report may still compare unlike scope. Old and new classification editions should not be mixed without a documented mapping. A code alone is not enough: description, project context and allocation rules must remain understandable.

BKP and Caturix

BKP remains the project’s overarching cost structure. Caturix supplies operational data from quotations, work items, projects, time and site reports. A contractor should define how its quotations and projects relate to the cost structure it uses, so that preliminary costing and final job costing compare the same work.

Frequently asked questions

What is the difference between BKP and NPK?

BKP groups costs by execution trade for planning and control. NPK provides standardised descriptions of individual construction work items for bills of quantities, quotations and valuation. An NPK item may be mapped to a BKP group, but the systems serve different purposes.

How does BKP differ from an element-based cost plan?

BKP is organised around execution trades. An element-based cost plan groups costs by building elements. The element view is often useful earlier in design, while the trade view becomes important for work packages, procurement and final accounts.

Is BKP used in Germany?

No. BKP under SN 506 500 is a Swiss classification. Germany typically structures building costs under DIN 276. Similar-looking group numbers should not be assumed to represent equivalent scope.

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