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Cost comparison worksheet
A developer built 26 high-end houses. Previous similar developments produced the figures below. Skilled labour cost this particular developer 56.00 per hour and helpers 29.00 per hour; those are not the paid wages but numbers that encompass all costs associated with employing the personnel.
Each home had two bay windows, a groin vault in the wine cellar, an elliptical dome in the foyer, and a large cove detail in the master bedroom.
Conventional site framing
| Element | Labour | Materials | Total |
|---|---|---|---|
| Bay window framing | Carpenter and helper, 26 hrs | 166.00 | 2,376.00 |
| Groin vault | Carpenter and helper, 32 hrs | 320.00 | 3,040.00 |
| Dome | Carpenter and helper, 22 hrs | 290.00 | 2,160.00 |
| Cove | Carpenter and helper, 19 hrs | 288.00 | 1,903.00 |
| Total | — | — | 9,679.00 |
Delivered assemblies
Complete precision parts and assemblies arrive at the job. Across 26 houses there is significant economy of scale, since engineering and tooling costs are spread out.
| Element | Site labour | Unit and delivery | Total |
|---|---|---|---|
| Bay window framing | 1 carpenter, 2 hrs | 825.00 | 1,999.00 |
| Groin vault | Carpenter and helper, 4 hrs | 1,125.00 | 1,465.00 |
| Dome | Carpenter and helper, 4 hrs | 1,448.00 | 1,788.00 |
| Cove | Carpenter and helper, 6 hrs | 956.00 | 1,466.00 |
| Total | — | — | 6,718.00 |
The bay window framing arrives pre-sheathed as a unit, ready to roof, and takes one carpenter two hours to install; the total above includes 224.00 of labour and an hour of all-terrain forklift at 125.00. The groin vault and the cove arrive as flat pack parts, predrilled for pocket screws and numbered with assembly drawings. The dome comes as a unit, ready for wire and plaster.
Difference
Across the four elements the recorded difference per house is 2,961.00, before counting the framing weeks that the delivered assemblies free up elsewhere on the schedule.
Categories: Custom assemblies | Window roofs