Signing the contract does not end negotiation; it relocates it. In kitchen ventilation projects, the second negotiation happens through change orders, and it is the one buyers lose most often, because by then the equipment is ordered, the programme is running and the supplier holds the schedule. A variation priced casually costs three to eight percent of a typical project value by handover, and almost none of it appears as one big number. It arrives as a series of plausible small extras. This guide is written for the buyer side: how to read the variation clause before signature, how to price each instruction, and how to keep a record that survives the final account.
Why Kitchen Projects Generate Variations
Ventilation work touches more of the building than almost any other kitchen trade: it penetrates the roof or the facade, runs through ceiling voids shared with electrical and fire systems, draws power from a distribution board someone else sized, and sits under the eye of the fire officer. Each of those interfaces is a variation trigger:
Survey mismatches. The ceiling void contains a beam the survey missed, or the wall the duct was to pass through turns out to be load-bearing. The route changes, metres are added, and a duct size may change with it.
Power reality. The assumed electrical supply point is full, or the breaker sizes in the approved schematic do not match the site’s distribution board, and a new supply route or an upgrade instruction follows.
Authority comments. The fire officer or building inspector asks for an additional fire damper, a re-routed penetration or extra fire-stopping after reviewing the approved drawings.
Menu and equipment changes. The operator adds a char-grill or swaps a combi oven for a range, and the airflow duty, hood length or purification stage configuration changes with it.
Coordination clashes. Another contractor’s services occupy the duct route first, and the ventilation package re-routes around them.
None of these is anyone’s fault in particular, and that is exactly why the variation procedure must be mechanical rather than adversarial. The contract already knows problems will occur; the question the clause answers is who prices what, on what basis, and how fast.
The Variation Clause: Read It Before Signature
Most of the variation pain later is manufactured at tender stage, when the clause is a paragraph nobody reads. Before signing, check five things in it:
1. Who may instruct. Variations are valid only when instructed by a named role: the employer, the architect or contract administrator, or the project manager. A site foreman saying “just move the fan” is not an instruction, and the buyer should not pay for work done on it. Conversely, if your own team gives verbal directions on site, the supplier is entitled to price them; the discipline runs both ways.
2. Written form and notice periods. The clause should require instructions in writing and give the supplier a fixed window, typically 7 to 14 days, to submit a quotation. It should equally bind the buyer: if you delay the quotation response, the supplier’s programme claim strengthens. Check whether verbal instructions must be confirmed in writing within a stated number of days; three to five is standard, and this confirmation habit is the single cheapest protection in the whole clause.
3. The pricing basis. The clause should state that variations are valued first at contract rates, second at rates derived from contract rates, and only where neither exists, at daywork rates or a lump quotation. A contract silent on this invites a fresh quotation for every extra, priced at the moment the buyer has least leverage.
4. Time and money together. Every variation quotation should state its programme effect, and every extension-of-time request should state its cost effect. Splitting them lets each side concede the cheap half and argue the expensive half forever.
5. Records and access. The clause should oblige the supplier to keep records of extra labour and plant when instructed, and to give the buyer’s representative access to them. Without this, daywork valuation becomes an argument about memory.
The Anatomy of a Valid Variation Instruction
An instruction that skips elements invites a quotation that skips accuracy. Every variation instruction, whether issued by the buyer or accepted from a consultant, should carry the same fields:
1. A unique reference number, tied to the project numbering scheme.
2. A precise description of the change: what is added, what is omitted, what is altered.
3. The reason, stated briefly: site condition, authority comment, employer’s change of mind.
4. The date of instruction and the required response date.
5. A first statement of programme effect, even if provisional.
6. Any provisional sum or daywork allocation to be used.
The reference number matters more than it looks. Quotes, site diaries, photographs and invoices that all cite the same number form a chain of evidence; without it, the final account is assembled from fragments. When a verbal instruction is unavoidable on site, the buyer’s site representative should send the confirmation email the same day using this template, with a photograph attached where the change is physical. A two-line email prevents most valuation disputes.
How to Price a Variation: Four Methods in Order
The pricing hierarchy is not legal decoration; each level is cheaper and faster to verify than the next. Push every quotation down the ladder before accepting a fresh price:
| Method | When it applies | Buyer check |
|---|---|---|
| Contract rates | The varied work matches a billed item: same duct size, same fixing type, same finish | Confirm the quantity extension uses the tender rate unchanged, not a “current” rate |
| Derived rates | The work is analogous: a 250 mm duct item repriced for 315 mm using the tender’s own proportions | Ask for the derivation in one line; a derived rate should move by material cost, not by round numbers |
| Daywork | Unquantifiable at instruction time: exploratory work, out-of-hours access, dismantling | Use the tender’s daywork schedule rates; cap hours by prior approval; audit signed time sheets weekly |
| Lump quotation | Distinct new packages: an added purifier stage, a second hood, a structural steel bracket | Request the build-up behind the lump; a quotation that arrives as one number is a negotiation, not a valuation |
Two rules sit above the table. First, omissions are credited at the same rates as additions: if ductwork is re-routed and five metres are saved, those metres come off at the tender rate, and the supplier cannot argue that saved work was never going to cost what was tendered. Second, markups apply once: labour, material, overhead and profit should appear as one structure, not as profit calculated on an overhead that was itself calculated on labour.
The Numbers to Check on Every Variation Quote
A variation quotation deserves ten minutes of arithmetic, not a signature. Work through the build-up:
Labour realism. Compare claimed hours against the tender’s own productivity: if the tender priced duct installation at a certain hours-per-metre, the variation on the same duct should price at the same hours, adjusted only for access conditions actually different. A variation quoting double the tender productivity needs a stated reason.
Material pricing. Materials should price at tender rates where identical, or at invoice cost plus the tender’s stated material uplift where new. Ask for the supplier’s purchase invoice on items over a threshold you set, commonly a few hundred euros; most suppliers accept this for one-off major items and it removes guessing.
Plant and supervision. Check that plant claimed for the variation is not already carried in the preliminaries the buyer is paying monthly, and that supervision is proportional. A half-day variation that carries a full day of supervision is a quiet margin, not a cost.
The deduction side. List what the variation removes. Re-routes save duct and hangers; a relocated fan saves a section of flexible connection. Quotations that price only the addition are half a quotation, and the register should not release payment until the omission credit is stated.
Compounding. Confirm overhead and profit percentages match the contract. If the tender stated 10 percent overhead and 8 percent profit on variations, a quotation applying 25 percent combined is a different contract, and the correction is mechanical rather than negotiable.
Time Impact: Variations Move the Programme
Every variation has a twin claim. Extra duct through a occupied ceiling area may need out-of-hours access; an added purification stage adds factory lead time; a re-route adds installation days. The variation procedure and the extension-of-time procedure are one system, and the buyer should insist they travel together:
1. The variation quotation states its programme effect in working days, with the critical path identified.
2. Acceptance of the price is acceptance of the stated time effect; the supplier cannot reopen it later.
3. Where the supplier claims more time than quoted, the claim cites records, not recollection: access logs, delivery notes, weather, photographs with dates.
4. A delay register records every event, its notification date and its resolution, mirroring the variation register.
This pairing is what keeps the liquidated damages clause honest in both directions. A buyer who prices variations but ignores time effects has agreed to pay for extras and still carry the delay risk they create.
The Variation Register
One table, one owner, updated weekly. The register is both a management tool and the skeleton of the final account:
| Column | Purpose |
|---|---|
| Reference number | Ties instruction, quotation, records and payment together |
| Description and reason | One line each; the reason drives the pricing method |
| Date instructed / quoted | Exposes clause breaches: quotations outside the notice window |
| Pricing method | Contract rate, derived, daywork or lump, per the hierarchy |
| Quoted sum and credit | Addition and omission side by side, never addition alone |
| Programme effect | Working days, with acceptance status |
| Status | Instructed / quoted / agreed / instructed in writing / in final account |
A running total against the contingency line converts a vague unease about “extras” into a number the finance team can see, and suppliers price more carefully to a buyer who visibly reconciles.
Six Traps That Erode the Budget
1. Verbal instructions priced later. Work done on a nod gets priced after the fact, at rates quoted when the work is already installed. Confirm in writing the same day, always.
2. Provisional sums converting with markup. A provisional sum spent should convert to actual cost plus the contract markup, not become a fresh lump quotation on top of the allowance.
3. The free-extras accumulation. Small favours are not free; they are unpriced liabilities. When a supplier asks for variation 14 to cover three earlier verbal requests, the buyer has lost the pricing race three times.
4. Variations used to close defects. Repairing defective work is the defects obligation, not a variation. Any quotation that prices the correction of faulty work is rejected on principle and in writing.
5. Omit-and-add arbitrage. Omitting a cheap-to-build item at its tender rate and adding a similar item at a fresh higher rate is a margin trick; the register’s credit column is what exposes it.
6. Pricing spikes after the freeze. Once drawings are approved and the configuration frozen, quotation rates should not drift from tender levels. Rate stability after approval is a contractual expectation, and drift is a negotiation signal rather than a cost fact.
A Worked Example: Adding Two Metres of Duct Route
Make the method concrete. The fire officer requires a duct route to shift two metres to clear a sprinkler zone. The tender priced 6 metres of comparable 315 mm duct at a stated rate per metre, installed. The variation prices as follows: two metres of duct and hangers at the tender rate, one additional bend priced as a derived rate from the tender’s bend items, four metres of additional duct removed from the original route credited at the same tender rate, half a day of additional access equipment at the tender’s plant rates, and a stated programme effect of two working days agreed in the same letter. The quotation, the credit and the time effect fit on one page, cite the instruction reference, and are agreed within the notice window. That is what a well-run variation looks like; everything else is negotiation at a disadvantage.
How Architecture Shrinks the Variation Surface
The number of variations a project generates is not luck; it follows from how many building interfaces the architecture creates. Every metre of duct through the building is a potential route clash, a potential fire-stopping instruction, a potential penetration reposition. A ductless all-in-one configuration removes most of that surface: capture, purification and recirculation happen inside one unit, so there is no duct route to clash, no penetration to reposition and no make-up air balancing to redo. When a site condition changes, the response is a relocation of a self-contained unit rather than a re-engineered duct run, and the variation, where one exists at all, prices in hours rather than days. For kitchens where the structure resists penetrations, the ductless range hood range is engineered around exactly that reduction in interfaces.
Within the ductless route the menu still picks the unit: light-fume lines fit a compact all-in-one hood, the N-series tier; heavy-fume lines with fryers and char-grills need the deeper treatment of the ND-series, with a separate Odor Removal Tower where odour limits are tight. The variation surface of these units concentrates in one question, the electrical supply, which the approved schematic should already have fixed. Where the duty genuinely requires a full duct run and high volume, the ducted route remains the engineering answer, and its variation discipline is the one described above, with the duct route as the main exposure: the ducted ESP purifier range serves that end. For cooking that moves between pitches and events, pre-engineered mobile units compress the variation question almost to zero, because the ventless catering cart line arrives as a factory package needing only a power point.
The buying logic is direct: choose the architecture that matches the building’s tolerance for change, and the change-order clause becomes a rarely used safety net instead of a second profit centre for someone else.
A Ten-Point Change Order Checklist
Print this beside the variation register:
1. The clause names who may instruct, and requires written form.
2. Notice windows for quotations are stated and calendared.
3. The pricing hierarchy runs contract rates first, daywork last.
4. Every instruction carries a reference number, description, reason and date.
5. Verbal instructions are confirmed in writing the same day.
6. Every quotation states its programme effect beside its price.
7. Omission credits are stated at contract rates before payment releases.
8. Markups match the contract percentages, applied once.
9. Provisional sums convert to actual cost plus contract markup.
10. The register is reconciled weekly against the contingency line.
Change orders are not an attack; they are the contract’s mechanism for absorbing the surprises every kitchen project contains. The buyer who reads the variation clause before signature, instructs in writing, prices through the hierarchy, pairs time with money and keeps a register ends the project with an extras bill that is explained line by line. The buyer who skips those habits ends it with a number, and an argument about how it got there.
