CONSTRUCTION ESTIMATE
Single Storey Rear Extension
14 Oakfield Road, London SW00 0AA
£128,788.03 excluding VAT
Contents
- 1. Executive Summary
- 2. Basis of Estimate
- 3. Drawings & Information Relied Upon
- 4. Pricing Summary by Stage
- 5. Preliminaries
- 6. Detailed Stage Breakdown
- 7. PC Sums & Provisional Sums
- 8. Value Engineering Options
- 9. Assumptions
- 10. Exclusions
- 11. Qualifications & Site Verification
- 12. Stage Payment Schedule
- 13. Next Steps
- 14. Standard Terms
1Executive Summary
This report sets out our estimate for the construction of a single storey rear extension at 14 Oakfield Road, London SW00 0AA, providing approximately 42 m² additional floor area. It has been prepared for Mr & Mrs Sample on the basis of the drawings and information listed in Section 2.
Net works£113,971.70
Net total (incl. OH&P + contingency)£128,788.03
Total incl. VAT£154,545.64
The net total of £128,788.03 includes overheads and profit at 8% and a construction contingency at 5%. With VAT at 20%, the total is £154,545.64.
The estimate carries PC and provisional sums totalling £27,414.00 for items not yet finally selected (Section 7). We have also set out value engineering options in Section 8 that could reduce the cost by up to £7,150.00 if adopted.
This is an estimate rather than a fixed-price tender. It should be read together with the assumptions, exclusions and qualifications, which define exactly what is and is not included. All dimensions must be verified on site before ordering or starting work.
Key figure: £128,788.03 net / £154,545.64 including VAT. Valid 90 days.
2Basis of Estimate
This estimate has been prepared on the following basis. Where information was not available, a reasonable allowance has been made and identified as a PC or provisional sum.
| Project | Single Storey Rear Extension, 42 m² additional floor area |
| Location | 14 Oakfield Road, London SW00 0AA |
| Scope | Construction of the extension including groundworks, structure, roof, external envelope, first and second fix, finishes, kitchen and sanitaryware installation, and associated external works. |
| Measurement | Quantities measured from the listed drawings in accordance with NRM2 principles. |
| Pricing | Current UK market labour and material rates at the date of issue. |
| Programme | Single continuous build assumed. No allowance for phasing or accelerated working. |
| Contract | Assumed a standard domestic building contract. Not yet agreed. |
If any of the above changes, in particular a drawing revision or a change of specification, the estimate should be revisited.
3Drawings & Information Relied Upon
This estimate is based on the following drawings and their revisions. Pricing relates to these revisions only. A later revision may change quantities and cost.
| Drawing | Title | Rev | Originator |
|---|
| A-100 | Existing plans and elevations | Rev C | Sample Architects Ltd |
| A-101 | Proposed ground floor plan | Rev D | Sample Architects Ltd |
| A-102 | Proposed elevations and section | Rev D | Sample Architects Ltd |
| A-200 | Proposed roof plan | Rev B | Sample Architects Ltd |
| S-01 | Structural layout and beam schedule | Rev B | Consulting Structural Engineer |
| S-02 | Foundation details | Rev A | Consulting Structural Engineer |
Important: all dimensions shown on these drawings must be confirmed on site before any materials are ordered or works commence. Figured dimensions take precedence over scaled dimensions in all cases.
4Pricing Summary by Stage
The table below summarises the net cost of each stage of the works, excluding VAT. Preliminaries are shown in Section 5 and a full breakdown of every stage follows in Section 6.
| Stage | Net (excl. VAT) |
|---|
| Preliminaries | £17,640.00 |
| Groundworks & Foundations | £10,452.40 |
| Superstructure & Walls | £21,350.00 |
| Roofing | £9,976.00 |
| Windows & External Doors | £8,020.00 |
| First Fix M&E | £6,478.00 |
| Internal Finishes | £15,585.30 |
| Kitchen & Sanitaryware | £17,550.00 |
| External Works | £6,920.00 |
| Net works | £113,971.70 |
| Overheads & profit @ 8% | £9,117.74 |
| Construction contingency @ 5% | £5,698.59 |
| Net total (excl. VAT) | £128,788.03 |
| VAT @ 20% | £25,757.61 |
Total including VAT£154,545.64
5Preliminaries
Preliminaries cover the cost of running the project that is not tied to a single trade, site set-up, management, access, welfare, temporary works and general attendance. They are listed as items and priced for a build of this size and duration.
| Item | Qty | Unit | Rate | Net |
| Site set-up, welfare unit and temporary fencing | 1 | item | £2,850.00 | £2,850.00 |
| Scaffolding to rear elevation, 12 week hire | 1 | item | £3,420.00 | £3,420.00 |
| Skip hire and waste removal, 6 x 8yd | 6 | each | £285.00 | £1,710.00 |
| Site management and supervision | 12 | week | £640.00 | £7,680.00 |
| Temporary services, protection and general attendance | 1 | item | £1,980.00 | £1,980.00 |
| Total preliminaries | £17,640.00 |
Preliminaries are time-related. A longer programme, or a stop-start programme, would increase this figure.
6Detailed Stage Breakdown
Each stage is broken down into its works. Under every work, costs are grouped into materials, labour and plant. Rates are net of VAT and reflect current UK market prices.
Groundworks & Foundations£10,452.40
Excavation & Disposal£3,516.80
| Description | Qty | Unit | Rate | Net |
| Labour |
| Reduce level dig and cart away spoil | 38 | m3 | £46.50 | £1,767.00 |
| Excavate for trench fill foundations | 22.4 | m3 | £52.00 | £1,164.80 |
| Plant |
| 3 Tonne excavator hire | 3 | day | £195.00 | £585.00 |
Foundations & Floor Slab£6,935.60
| Description | Qty | Unit | Rate | Net |
| Material |
| Ready-mix C25 concrete | 22.4 | m3 | £142.00 | £3,180.80 |
| Sand blinding and 1200g DPM | 42 | m2 | £9.80 | £411.60 |
| 100mm PIR floor insulation | 42 | m2 | £21.40 | £898.80 |
| Labour |
| Pour foundations, lay and power-float slab | 42 | m2 | £58.20 | £2,444.40 |
Remaining stages (Superstructure, Roofing, Windows, M&E, Finishes, Kitchen, External Works) follow in the full document, each priced the same way.
7PC Sums & Provisional Sums
The items below are allowances, not fixed prices. A Prime Cost (PC) sum is money set aside for materials or fittings not yet finally selected. A provisional sum is money set aside for work that cannot yet be precisely measured.
| Item | Type | Allowance (excl. VAT) |
| Facing bricks to match existing | PC Sum | £2,304.00 |
| Rooflights (2 no.) | PC Sum | £2,500.00 |
| Aluminium bi-fold doors, 3.6m | PC Sum | £4,200.00 |
| Windows to extension (4 no.) | PC Sum | £2,720.00 |
| Floor finish supply | PC Sum | £1,890.00 |
| Kitchen units and worktops | PC Sum | £12,000.00 |
| Sanitaryware to WC | PC Sum | £1,800.00 |
| Total allowances | £27,414.00 |
8Value Engineering Options
The following options could reduce the cost without changing the size or layout of the extension. They are optional. Each shows the saving against the net total.
| Option | Area | Saving |
| Single-ply membrane roof to a high-performance felt system Proven felt build-up. Slightly shorter guarantee period. | Roofing | −£1,260.00 |
| Aluminium bi-fold to uPVC French doors with side lights Lower-cost door set. Reduces the slimline appearance. | Windows | −£2,350.00 |
| Client-supplied kitchen Client procures kitchen directly. MPE installs only. | Kitchen | −£2,000.00 |
| Maximum saving if all options adopted | −£7,150.00 |
Net total as estimated: £128,788.03, with all options: £121,638.03 (excl. VAT)
Standard Terms
This estimate is issued as an estimate of likely cost based on the information available at the date of issue and is not a fixed-price tender or an offer to contract. Prices are held for 90 days from the date of issue. Quantities are measured from the drawings listed and must be verified on site before ordering or commencing works. PC and provisional sums are allowances only and are reconciled against actual cost.