Worked example: three quotes for one warehouse roof
A common situation on a profiled-metal warehouse roof: one firm quotes a coating, another an over-sheet with new insulation, and a third a full re-clad. The prices look like a bidding war, but they are three different jobs. This worked example shows how to tell which one fits the fault. It is an illustration of the method, not an account of a real building or client, and it uses no prices.
The situation
The building is a single-storey steel-framed warehouse with a profiled-metal roof, valley gutters and rooflights, in use throughout. There are drips inside after heavy rain, rust at the sheet ends, and the facilities manager has three quotes on the desk.
What each quote is really proposing
| Quote | Scope | Fits when | Questions to ask |
|---|---|---|---|
| A: coating | Clean, treat cut edges, apply a liquid coating over the sheets | Sheets and fixings are sound and the leak is at laps or cut edges | Are the gutters included? What guarantee applies, and on what conditions? Does it deal with the rooflights? |
| B: over-sheet | New spacer system, insulation and outer sheets over the existing roof | The structure can take the extra load and the existing sheets can stay as a liner | Has the structure been checked for the added load? What U-value does it reach? How are gutters and rooflights detailed? |
| C: full re-clad | Strip the old sheets and fit a new insulated roof | Sheets are failing, or the existing roof contains asbestos that must come off | How is the building protected while it is open to the weather? What happens to asbestos sheets, if present? |
Reading the fault first
The three scopes answer different faults, so the first question is what is actually leaking. On large profiled-metal roofs, failed valley or box-gutter joints and cut-edge corrosion at the sheet ends are frequent causes of internal leaks, and they can be missed by a quote that only looks at the sheets. Ask each firm what evidence it has for the cause: a roof inspection, photographs of the gutters and laps, a water test. A quote that does not name the cause is pricing a guess.
Putting the quotes on one basis
- Check that all three cover the same roof area and say whether it is measured on plan or along the slope.
- Take gutters out of the area rate and compare them as a separate line, since some firms price them per linear metre and some leave them out.
- Add access, edge protection and rooflight protection back into any quote that shows them as "by others".
- Note whether the building went up before 2000. If so, ask whether an asbestos refurbishment survey has been done, as HSE guidance expects before work that disturbs the roof fabric.
Comparing the six lines
Once the scopes are clear, line the quotes up on the system, the falls, the insulation and U-value, the guarantee, the access plan and the exclusions. The coating may carry the shortest guarantee and no insulation upgrade. The over-sheet may bring the roof up to a better U-value, and if it renews most of the roof the Part L insulation requirements for a renovated element are likely to apply. The re-clad may be the only option if the sheets have failed or contain asbestos that must be removed.
What the facilities manager can decide
If the inspection shows sound sheets with failed gutters and cut edges, a gutter lining with cut-edge treatment, perhaps with a coating, may answer the fault, and the comparison is between A and a revised A. If the sheets are near the end of their life, the choice is between B and C on structure, insulation, guarantee and disruption. In each case, the useful outcome is three quotes for the same scope, so the price difference that remains is real.
Try the comparison on your own figures with the quote sense-check, and see the industrial cladding guide and the roof coatings guide for system detail.
Worked example for illustration only. Not a real building, job or client. Last checked 25 October 2026.