THE ESTIMATING ANSWER
Estimate roof window replacement by measuring the defined one existing roof opening, separating product allowances from labour and setting out the work sequence and exclusions. This fictional Leeds example uses 7 itemised lines totalling £2,416.00; its exact quantities and rates appear in the paired app PDF.
The worked job is one existing roof opening in Leeds. The written scope is: Replace one roof window or skylight in the existing suitable opening, with matching flashing kit and interior edge repair. 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.
Skylight replacement: separate the roof opening from the glazing allowance
A skylight replacement quote should confirm whether the existing opening can remain and identify the exact replacement unit. Record the visible dimensions, roof covering, interior shaft finish and any signs of leakage for the roofer's review. A like-for-like replacement and an enlarged opening are different jobs even when the glazing area looks similar in a product catalogue or a photograph.
Keep the selected skylight, compatible flashing, removal, roof access, fitting and internal making good as separate allowances. Ask who checks the existing surrounding material and how discovered damage will be priced. Interior edge repair, complete shaft redecoration and structural alteration should each be described explicitly; they should not be inferred from the phrase replace one skylight on a quotation.
Share the same roof photographs and opening information with each supplier. Confirm whether product measurement, temporary weather protection and waste removal are included. Compare the full installation scope before comparing the product allowance, and keep any concealed roof damage as a documented change trigger.
A separate worked planning example
Illustrative comparison: one existing opening, one selected replacement skylight and one matching flashing set. Count interior repair as its own measured or fixed allowance. This example does not set an opening size or establish that an old and new product are interchangeable.
Cost and scope questions
Can I quote a replacement using the visible glass size?
Use that measurement only as preliminary information. The installer must confirm the product dimensions, opening and flashing arrangement before selection or fabrication.
Does a skylight replacement include repainting the whole ceiling?
Only when named in the scope. A local interior edge-repair allowance is different from repainting the shaft or the whole room.
1. Define the measured job
Replace one roof window or skylight in the existing suitable opening, with matching flashing kit and interior edge repair. Measure the structural opening, roof covering type, pitch and interior reveal. 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 the structural opening, roof covering type, pitch and interior reveal. 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
Keep unit, manufacturer-matched flashing and interior finish allowance separate. This example has 7 distinct lines, including opening and access survey, temporary roof protection, old skylight removal. Use actual supplier prices and labour inputs for a customer job; the displayed amounts are fictional document inputs.
Choose before pricing: Keep unit, manufacturer-matched flashing and interior finish allowance separate. 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
Confirm product and safe roof access before removing the old unit. 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: Confirm product and safe roof access before removing the old unit. 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
Rotten curb or incompatible opening changes framing and waterproofing scope. The example excludes new roof opening, ceiling refurbishment or concealed structural repair. Record the discovery, agree the revised work and update the estimate before adding it to the job.
Change trigger: Rotten curb or incompatible opening changes framing and waterproofing scope. 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, Opening and access survey is 1 lump sum × £200.00 = £200.00; Temporary roof protection is 1 lump sum × £184.00 = £184.00. 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 |
|---|---|---|---|
| Opening and access survey | 1 lump sum | £200.00 | £200.00 |
| Temporary roof protection | 1 lump sum | £184.00 | £184.00 |
| Old skylight removal | 1 each | £232.00 | £232.00 |
| Skylight unit allowance | 1 each | £840.00 | £840.00 |
| Flashing kit allowance | 1 set | £216.00 | £216.00 |
| Installation and weathering | 1 each | £496.00 | £496.00 |
| Interior trim and clean-up | 1 lump sum | £248.00 | £248.00 |
| Illustrative total | £2,416.00 | ||
Adding the 7 exact line amounts gives £2,416.00. 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 one roof window or skylight in the existing suitable opening, with matching flashing kit and interior edge repair.
Outside this example: No new roof opening, ceiling refurbishment or concealed structural repair.
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 the structural opening, roof covering type, pitch and interior reveal.
- Keep unit, manufacturer-matched flashing and interior finish allowance separate.
- Confirm product and safe roof access before removing the old unit.
- Rotten curb or incompatible opening changes framing and waterproofing scope.
Compare the written scope with every line in the roof window 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 roof window replacement estimate?
Measure the structural opening, roof covering type, pitch and interior reveal.
When should this roof window replacement quote be revised?
Rotten curb or incompatible opening changes framing and waterproofing scope. No new roof opening, ceiling refurbishment or concealed structural repair.
FROM SITE NOTES TO AN ITEMISED PDF
Build your own roof window 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.
