Two quotes for the same roof: why they differ, and what to ask

You hold two or three quotes for your roof or roof terrace, and the totals are far apart. The natural reaction is to wonder who is right. The more useful question is a different one: do they all describe the same job?

This is written by a contractor, so we have an interest. That is why this article carries no prices and no comparison with anyone; our own indicative prices are published separately, on the Prices page. You will find what to check on the paper you are holding — whoever signed it, ourselves included.

Why do two quotes for the same roof come out so differently?

Because the word "roof" or "waterproofing" on the first line does not say what will be done. Two quotes with the same title can differ on five points that change the cost:

• what is removed, and where it ends up;
• which layers go in, and at what thickness;
• how much time is given to the points where failures appear — edges, junctions, penetrations;
• what is inside the price: VAT, scaffolding, disposal;
• what is handed over in writing at the end.

When these are not written down, the comparison happens on the total alone. And the total does not show what you are buying.

What should a complete roof or flat-roof quote include?

• Removal: what comes off — tiles, old layers, boarding, finishes — and to what depth; what is allowed for any damaged timber.
• Disposal of the removed material, legally and with a receipt.
• Scaffolding or other access, and the safety measures for work at height.
• Every layer named by product and thickness or coverage per m²: insulation, membranes, ventilation gap, waterproofing coating, final covering.
• Valleys, gutters, downpipes, terminations, parapets, junctions with walls and chimneys, pipe penetrations.
• Falls and drainage: on a flat roof, whether the falls to the outlets are corrected, and how many outlets there are.
• Insurance for the people who will work on your building.
• VAT: the final amount including VAT, in writing.
• Permits and registration: whether the work needs an approval or a registration, who handles it, and whether it is inside the price. Your engineer can confirm this.
• Payments: deposit and stage payments, in writing.
• Warranty: duration, what it covers and what voids it, as text.
• Handover: what you receive at the end — photographs of the layers that were covered, maintenance instructions.
• Exclusions: what is not included, by name.

None of these is a luxury. If something is missing from the paper, it does not necessarily mean it will not be done; it means it has not been agreed.

Which 10 questions should I ask of every quote?

1. What is the final amount, and is VAT included?
2. What exactly is removed, and where does the removed material go?
3. Which layers go in, under which product name and at what thickness or coverage each?
4. In which layer does the waterproofing sit, and what lies on top of it?
5. Are the edges, parapets, wall junctions and pipe penetrations included? How many?
6. Are scaffolding, lifting equipment and safety measures inside the price?
7. Are the people working on my building insured?
8. What is not included? Can you list it by name?
9. What does the warranty cover, for how long, and what voids it — in writing?
10. What will I hold when the work is finished: photographs of the concealed layers, maintenance instructions?

You do not need to be an engineer to ask them. A serious answer is specific and written. If one is missing, ask for it in writing before you sign, from whoever gave you the quote.

If two quotes answer everything, why do they still differ?

For many reasons, not always to do with quality: overheads and travel, availability, crew size, margin. One reason worth asking about is the time spent where nobody looks. Many problems appear where the material ends or is interrupted: edges, corners, outlets, junctions. On a flat roof the falls to the outlets matter too: where water ponds, the waterproofing ages faster. Those points take hours, and they do not show in the photograph of the finished job.

Ask how they are detailed, and how watertightness is checked before they are covered. The same goes for materials: two membranes of the same category can differ in thickness or strength. That is why question 3 asks for a product name, not a category.

What happens if, once the roof is opened, something turns up that could not be seen?

It happens: a rotten timber under the tiles, a wet layer under the finish. Nobody can see it before the construction is opened, so no quote can price it with certainty.

What a quote can state is how it will be handled: that you will be told before work proceeds, with photographs, and that the extra work will be priced in a way you know in advance. Ask before you sign. A change in the final amount that is explained and agreed is a different thing from a change that appears on the invoice.

How do I know what went in under the tiles or the terrace finish?

With certainty, only if it was photographed before it was covered. Material invoices show what was bought, not how it went in. A finished roof looks the same whether the layers beneath it are right or not. A photographic record of every layer is the evidence that remains: for you, for the next tradesman, for a buyer if you sell. Ask for it as a deliverable, written into the quote.

How does Roof Energy work?

We start with a site survey, so the quote describes your specific building. The quote states what is included and what is excluded. The founder works on site and supervises the critical points, such as terminations and finishes.

Every stage is photographed as it is built, particularly the layers about to be covered, and the record is handed to the owner at no separate charge, together with maintenance instructions. 5-year written warranty (terms in the contract), extendable through our maintenance programme. This warranty does not affect your statutory rights. More on our method.

You will not find a price here. It depends on the building, and it is written in the quote.

What if I do not yet know what my roof needs?

Then comparing quotes is premature. Before a purchase, a sale or a major repair, our Roof condition report (a paid service) — or an equivalent inspection by an engineer — records, with photographs, what was checked and in what state — and what was not checked. With that in hand, every quote can answer the same question.

Keep the 10 questions. They are useful whichever quote you choose.