What are Provisional Cost Sums (PC Sums) - and how do they become fixed costs?
In refurbishment projects, certain elements are priced as PC Sums (Provisional Cost Sums) where final selections or layout decisions have not yet been confirmed. A provisional cost is simply a structured allowance - a realistic placeholder that lets the project move forward without waiting for every decision to be finalised.
Understanding what PC Sums are, why they exist, and how to convert them into fixed costs is one of the most important things a client can know before committing to a refurbishment budget.
Why Provisional Cost Sums are used
Bathrooms, kitchens and internal refurbishments contain multiple variables that directly affect labour time, compliance requirements and material costs. Without a confirmed specification backed with clear measurements, pricing would either be inaccurate or would include excessive contingency to protect the contractor - neither of which is good for the client. A provisional sum is more honest than a guess dressed up as a fixed price.
What determines the cost of a bathroom?
- Toilet type - close-coupled, back-to-wall, wall-hung with concealed cistern
- Shower system - concealed or exposed, thermostatic, number of diverters
- Bath versus walk-in shower versus wet room
- Tile size, material, thickness, pattern and height of tiling
- Underfloor heating versus towel radiator
- Ventilation - existing fan versus new installation
- Relocation of pipework or soil pipes
- Condition of existing walls and floors (tanking required or not)
What determines the cost of a kitchen?
- Like-for-like replacement versus full redesign
- Moving the sink or cooker positions
- Gas installation or new gas line versus no gas appliances
- Electrical load requirements - induction hobs, double ovens
- Number of base, wall and tall units
- Drawer count, handleless units, push-to-open mechanisms
- Worktop type - laminate, solid timber, quartz, granite, Dekton
- Appliance integration and lighting design
- Extractor type - recirculating versus external duct
Other items commonly priced as provisional
- Flooring - LVT, engineered wood, tile, pattern choices, trims and fixing method
- Decorating - paint specification, brand choice, specialist or feature wall finishes
- Internal doors - thickness, glazed or solid, sliding, pocket or swing, fire rating, ironmongery grade
- Radiators - quantity, style, size, valves, relocation
- Electrical fittings - lighting fixtures, quantity, manufacturer, finish
- Bespoke joinery - wardrobes, alcove shelving, under-stair storage, coffee stations
How Bayocorp converts PC Sums into fixed costs
Once design, layout, product selections and finishes are confirmed, provisional allowances are reviewed and replaced with fixed prices before work starts. This is a structured process, not an afterthought. We issue a revised schedule showing which lines have moved from provisional to fixed, what the cost impact is, and what has changed.
Clear selections before commencing on site allow accurate, transparent and controlled budgeting - which is why we push clients to make decisions early. The decision timeline matters as much as the budget itself.
Bayocorp rule: We never just add contingency and call it a fixed price. If something is genuinely unknown at tender stage, we say so, quantify it as a provisional sum, and lock it down before work starts - not after.