THE ESTIMATING ANSWER
Estimate flat roof membrane replacement by measuring the defined one low-slope extension roof, separating product allowances from labour and setting out the work sequence and exclusions. This fictional Cardiff example uses 7 itemised lines totalling £13,543.64; its exact quantities and rates appear in the paired app PDF.
The worked job is one low-slope extension roof in Cardiff. The written scope is: Replace the waterproof membrane on one accessible low-slope extension roof with defined edge and outlet details. Its matching itemised example shows how that description becomes quantities, allowances and a PDF. These figures are fictional inputs for learning the method, so check the real site, specification and supplier or subcontractor costs before quoting.
1. Define the measured job
Replace the waterproof membrane on one accessible low-slope extension roof with defined edge and outlet details. Measure net roof area, upstands, penetrations, drainage falls and perimeter edge length. Record the measurements and existing condition in the estimate before turning quantities into line items. The scope should make clear why this is a separate project from a broader renovation or maintenance quote.
Measure for this job: Measure net roof area, upstands, penetrations, drainage falls and perimeter edge length. Record the measured basis next to the relevant cost lines, since a room count, fitted length and purchased product quantity may each use a different unit.
2. Build a product and labour schedule
Identify membrane system, insulation if selected and outlet components separately. This example has 7 distinct lines, including access and temporary weathering, old membrane removal, deck preparation. Use actual supplier prices and labour inputs for a customer job; the displayed amounts are fictional document inputs.
Choose before pricing: Identify membrane system, insulation if selected and outlet components separately. Keep a named allowance when the selection is open, and replace it once the actual product and delivery terms are known.
3. Sequence the work and handoffs
Inspect deck condition after stripping and maintain temporary weather protection. Show which task depends on access, a selected product or another trade. If that dependency is still open, label the price preliminary and identify the information needed before a firm quote.
Plan the handoffs: Inspect deck condition after stripping and maintain temporary weather protection. State which stage needs access or inspection before the next can begin, especially if a concealed condition might stop the work.
4. Set a change boundary
A wet or unsound deck changes replacement quantity and system specification. The example excludes roof deck reconstruction, structural falls correction or interior repairs. Record the discovery, agree the revised work and update the estimate before adding it to the job.
Change trigger: A wet or unsound deck changes replacement quantity and system specification. If this happens, write down the revised quantity and responsibility before adding an item to the customer estimate.
Worked project calculation
The paired PDF has 7 cost lines. For example, Old membrane removal is 39 sq m × £51.67 = £2,015.13; Deck preparation is 39 sq m × £34.44 = £1,343.16. Each amount is the stated quantity multiplied by its unit rate. Recheck whether a line describes installed work, a material purchase allowance or a distinct visit before changing its quantity.
| Work item | Quantity | Unit rate | Amount |
|---|---|---|---|
| Access and temporary weathering | 1 lump sum | £520.00 | £520.00 |
| Old membrane removal | 39 sq m | £51.67 | £2,015.13 |
| Deck preparation | 39 sq m | £34.44 | £1,343.16 |
| Membrane system allowance | 42.7 sq m | £94.70 | £4,043.69 |
| Membrane installation | 39 sq m | £111.94 | £4,365.66 |
| Upstands and outlet details | 1 lump sum | £920.00 | £920.00 |
| Waste and final check | 1 lump sum | £336.00 | £336.00 |
| Illustrative total | £13,543.64 | ||
Adding the 7 exact line amounts gives £13,543.64. The PDF uses a 0% tax input and no markup solely to display this arithmetic. Decide the appropriate tax, overhead and profit treatment for an actual job; the fictional rates are not local averages or price recommendations.
Scope and price boundaries
Replace the waterproof membrane on one accessible low-slope extension roof with defined edge and outlet details.
Outside this example: No roof deck reconstruction, structural falls correction or interior repairs.
The role in this brief is roofing contractor. Confirm who supplies the selected products, makes the site safe, removes waste and signs off the work. Where opening up reveals a different condition, document it and issue a revised scope and price rather than silently extending the base estimate. Also check access, drying or curing time, and the client handoff described in the work sequence.
Before you send
- Measure net roof area, upstands, penetrations, drainage falls and perimeter edge length.
- Identify membrane system, insulation if selected and outlet components separately.
- Inspect deck condition after stripping and maintain temporary weather protection.
- A wet or unsound deck changes replacement quantity and system specification.
Compare the written scope with every line in the flat roof membrane replacement PDF example. The preview below is the first page of the actual app export; open the PDF to inspect its full scope, notes and amounts.
Questions about this job
Which quantity controls this flat roof membrane replacement estimate?
Measure net roof area, upstands, penetrations, drainage falls and perimeter edge length.
When should this flat roof membrane replacement quote be revised?
A wet or unsound deck changes replacement quantity and system specification. No roof deck reconstruction, structural falls correction or interior repairs.
FROM SITE NOTES TO AN ITEMISED PDF
Build your own flat roof membrane replacement estimate
Enter the project boundary and your measured lines in Estimates on iPhone or Android. Edit the fictional quantities and rates, add the actual business and client details, then inspect the PDF before sharing it.
