How to compare commercial roofing quotations on the same basis
Two quotations arrive for the same building. The lower total looks attractive, but one includes rooflights and the other retains them. Neither document says clearly who supplies the internal access.
Compare commercial roofing quotations by aligning the scope and responsibilities before comparing the totals. Record confirmed inclusions, exclusions, provisional allowances and costs retained by the client. Do not fill an unanswered item with zero and call the comparison complete.
This is a practical worksheet for quotations already received. For the initial briefing stage, use TCR's roof replacement quotation checklist.
Start with one agreed basis of comparison
Identify the roof zones, required assembly, rooflights, drainage, access, operating restrictions and completion requirements. Use the same drawings and revision numbers for each tenderer.
Where the tenderers propose genuinely different solutions, show them as alternatives rather than pretending they are identical. A coating proposal and a replacement proposal may both deserve consideration, but their totals do not represent the same work.
The comparison should make the choices visible so the client can decide what result is required before negotiating a price for it.
Give each item a clear status
Use “included”, “excluded”, “provisional” and “not confirmed” rather than a simple tick where the wording is uncertain. Add a note explaining the quantity, specification or boundary.
| Item | Quotation A | Quotation B | Clarification required |
|---|---|---|---|
| Main roof construction | Stated assembly and roof zones. | Stated assembly and roof zones. | Are the construction and measured areas equivalent? |
| Rooflights | Included quantity or retained condition. | Included quantity or retained condition. | Do both proposals provide the same outcome? |
| Gutters and outlets | Defined work or exclusion. | Defined work or exclusion. | Where does each drainage scope end? |
| Access and protection | Listed arrangements and duration. | Listed arrangements and duration. | Are client provisions and hire periods aligned? |
| Occupied building | Assumed restrictions and working hours. | Assumed restrictions and working hours. | Can the business provide both sets of assumptions? |
| Completion | Required inspections and documents. | Required inspections and documents. | Is the same completion evidence included? |
A difference is not automatically a mistake. It is something to understand and, where necessary, price on the same basis.
A worked comparison with deliberately fictional figures
The following numbers are invented solely to demonstrate the arithmetic. They are not TCR prices, market rates or an estimate for a real roof. All figures in this example are excluding VAT, and the tax treatment has not been assessed.
Assume both quotations have already been checked for the same main roof scope. Quotation A is £90,000 but excludes three required items. Confirmed supplementary prices for the illustration are £6,000 for rooflights, £4,000 for gutter work and £5,000 for the required access arrangement.
Quotation B is £103,000 and includes those same items. No other differences are assumed in this simplified example.
| Comparison | Quotation A | Quotation B |
|---|---|---|
| Headline quotation | £90,000 | £103,000 |
| Required rooflights outside headline price | £6,000 | Included |
| Required gutter work outside headline price | £4,000 | Included |
| Required access outside headline price | £5,000 | Included |
| Comparable scoped total in this illustration | £105,000 | £103,000 |
The initially lower quotation becomes £2,000 higher on the stated common scope. That does not prove B is the right contractor: specification, competence, programme and terms still need review. It shows why headline totals alone are insufficient.
In a real comparison, obtain actual prices for excluded items. Do not invent allowances to make one tender look more attractive.
Keep unknowns out of the confirmed total
If an item is not confirmed, record it separately with an owner and the clarification required. A provisional allowance should show what remains undefined and how the final price will be agreed.
Do not present a provisional sum as a guaranteed ceiling unless the terms actually establish that. Likewise, avoid adding a generic contingency and claiming it resolves every concealed condition.
The comparison can show a confirmed scoped total alongside unresolved exposure. That is more honest and more useful than one falsely precise number.
Check quantities and intended outcomes
Where rooflights are included, compare numbers, locations and the proposed treatment. Replacing units, retaining them and closing openings with opaque sheets are different instructions.
For gutters, distinguish cleaning, local repair, lining, replacement and outlet alterations. For roof construction, identify which layers are removed and retained. These distinctions can change the project even when the quotations use similar headings.
Ask tenderers to explain any departure from the common brief. Keep an alternative proposal visible instead of silently adjusting its description to match a competing return.
Compare responsibilities and timing as well as money
List what each quotation requires from the client: internal clearance, specialist isolations, access, shutdowns or use of neighbouring land. Establish whether those provisions are feasible and whether you retain a separate cost.
Check proposed start conditions, procurement assumptions, working hours and the basis of the programme. An earlier date is not an advantage if it depends on approvals or access that cannot be provided.
For safety related scope, ask the competent project team to assess suitability. Do not use the comparison exercise to remove necessary controls simply because another quotation omitted them.
Send one focused clarification request
Please confirm your price against the attached common scope and current drawings. Identify any departures, excluded items, provisional allowances, client provisions and decisions required before your programme can be confirmed. Please separate alternatives from the base proposal.
Then update the comparison with the written answers and retain the earlier versions. The final accepted scope should incorporate the agreed clarifications rather than depend on everybody remembering a telephone discussion.
Need a defined commercial roofing proposal you can assess properly? Send TCR the project brief, specification and current drawings. Identify unresolved scope questions and your appointment timetable. We will review the information and confirm the appropriate next step for pricing or survey.
