Undefined provisional sum
A provisional sum is an allowance (or best guess), usually estimated by a cost consultant, that is inserted into tender documents for a specific element of the works that is not yet defined in enough detail for tenderers to accurately price.
A provisional sum can be categorised as ‘defined’ or ‘undefined’.
Undefined provisional sums are less well described as they refer to work which is not completely designed. As such, the contractor cannot be expected to make allowance for them in their programming, planning and pricing preliminaries. This means the contractor may be entitled to an extension of time and/or additional payments when the actual works are undertaken.
An example of an undefined provisional sum might be work required below an existing structure, where the ground conditions, and so the extent of work required, cannot be determined until the structure is demolished and the ground opened up.
With undefined provisional sums, the client typically bears the price and scheduling risks.
Defined provisional sums are those which have been described in sufficient detail that the contractor is expected to have made allowance for them in their programming, planning and pricing preliminaries.
[edit] Related articles on Designing Buildings
Featured articles and news
Creativity, conservation and craft at Barley Studio. Book review.
The challenge as PFI agreements come to an end
How construction deals with inherit assets built under long-term contracts.
Skills plan for engineering and building services
Comprehensive industry report highlights persistent skills challenges across the sector.
Choosing the right design team for a D&B Contract
An architect explains the nature and needs of working within this common procurement route.
Statement from the Interim Chief Construction Advisor
Thouria Istephan; Architect and inquiry panel member outlines ongoing work, priorities and next steps.
The 2025 draft NPPF in brief with indicative responses
Local verses National and suitable verses sustainable: Consultation open for just over one week.
Increased vigilance on VAT Domestic Reverse Charge
HMRC bearing down with increasing force on construction consultant says.
Call for greater recognition of professional standards
Chartered bodies representing more than 1.5 million individuals have written to the UK Government.
Cutting carbon, cost and risk in estate management
Lessons from Cardiff Met’s “Halve the Half” initiative.
Inspiring the next generation to fulfil an electrified future
Technical Manager at ECA on the importance of engagement between industry and education.
Repairing historic stone and slate roofs
The need for a code of practice and technical advice note.
Environmental compliance; a checklist for 2026
Legislative changes, policy shifts, phased rollouts, and compliance updates to be aware of.