Contingency and additional allowances

A reserve for remaining scope and changes

Contingency is a user-selected budget provision for residual construction risk. It is different from a cost line’s low/high range. Bilby does not interpret “high” as a guarantee that every unexpected event is covered, and the contingency percentage is a budgeting policy rather than a contractor’s market price.

The base avoids counted risks

For a selected contingency without an existing amount, budget enrichment starts from counted construction lines outside associated costs. It excludes separately itemised risk reserves and “other costs” allowances, then subtracts itemised risks already included within parent amounts. Associated costs, land purchase, finance and contingency itself do not form this construction base.

This matters when rock, piling or another risk already has a line: blindly applying the reserve to every amount would reserve money for that same risk twice. An actual/manual contingency remains the chosen amount rather than being continually replaced by the reference percentage.

Amounts behind the reserve

The eligible subtotal uses expected counted amounts, not a fresh low/base/high subtotal for each percentage.

Compute the eligible base before multiplying

Reference reserve = eligible expected construction subtotal × selected scenario fraction; the budget display rounds to whole kronor. The formula has no extra minimum when a valid base is known; a supplied zero base yields zero. The fallback reserve is for a missing or invalid dependency. Optional allowances elsewhere retain their own relevance and ownership: selecting them is not permission to sum an included detail twice.

Fictional budget reconciliation

Suppose counted construction is SEK 3,400,000, including SEK 200,000 of itemised risk and SEK 200,000 of other-cost allowances. The eligible base is SEK 3,000,000. The reference contingency is SEK 150,000 / 300,000 / 450,000. Adding SEK 1,000,000 for land does not increase that base. If a separate SEK 50,000 risk detail is already inside a parent amount and was not yet deducted, deduct it too: the expected reserve becomes 10% × SEK 2,950,000 = SEK 295,000.

Review overlap as the design becomes clearer

Replacing a vague risk allowance with a measured cost can alter both the construction sum and residual reserve base. Increasing your budget target alone does not change quantities or rates. A missing investigation does not become safe because a reserve exists. Review exclusions, supplier inclusions and contingency after each substantive quote. Do not stack several percentage reserves for the same uncertainty without identifying what each covers.

Method and review

This is Bilby’s explicit budget policy in reference-cost V1 and current budget completion logic, reviewed 18 October 2026. Its 5/10/15% fractions are not attributed to SGU, a municipality, a bank or a survey of contractor prices. The reference dataset’s research date remains 16 September 2026. Your line-item details identify the actual amount and inclusion status used in the project.