What Causes Construction Costs to Increase?
By Pilgrim Mill Construction · Published November 10, 2026 · Updated November 10, 2026
The short answer
Construction costs most commonly increase because of incomplete scope, owner changes after construction starts, unforeseen site or existing conditions, unrealistic allowances, material price changes and schedule delays. Thorough planning, clear documentation and contingency reduce — but cannot eliminate — these risks.
Incomplete scope
Anything not clearly defined in drawings and specifications is likely to become a change order.
Changes during construction
Changes are least expensive on paper and most expensive after work is installed.
Unforeseen conditions
Rock, poor soils, hidden water damage or outdated wiring can only be fully known once work begins. Investigations before construction reduce uncertainty.
Allowances and pricing
Low allowances and volatile material prices can both widen the gap between estimate and final cost.
Reducing surprises
Use contractor input during design, investigate site conditions, set realistic allowances, carry contingency and make decisions on schedule.
For a practical view of how budgets, decisions and project records are coordinated, explore Pilgrim Mill Construction’s construction project management approach.
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