Estimate tasks breakdown
Construction estimate tasks: the full breakdown by phase
A construction estimate is really a stack of small, priced decisions. Break the job into phases, break each phase into tasks, and the whole number becomes something you can check, defend and bill against. Here is the anatomy of a UK build, task by task.
Why it matters
Why price a job task by task
A lump sum wins nothing and protects nothing. A task-level breakdown is what keeps an estimate honest, quick to build and easy to bill.
Nothing hides in a lump sum
When every task carries its own quantity and price, forgotten work and quiet under-pricing have nowhere left to hide.
Faster, safer pricing
Work through the job phase by phase and you price in a logical order, from the ground up, so nothing gets skipped.
A schedule you can bill against
Tasks grouped into phases map straight onto site milestones, so payment applications follow real progress.
Clear conversations with clients
An itemised breakdown turns a single scary number into a list a client can read, question and sign off with confidence.
Every phase
From preliminaries to provisional sums, phase by phase
Every extension follows the same broad arc. These are the phases BEX AI prices, in order, each shown with the kind of tasks it holds.
Preliminaries
Site setup, protection, welfare and temporary works for the duration of the project.
- Install site security and temporary boarding
- Supply and install scaffolding (per storey of elevation)
- Supply portaloo including delivery
- Small site Health and Safety (allowance)
Demolition
Strip the existing ground surface and open up the host wall for the new connection.
- Strip off and level existing ground, remove soil from site
- Demolish external walls and clear the rubbish away
Foundations and Footings
Trench foundations, footings to DPC and reinforced ground beam at the structural opening.
- Excavate and cast trench foundations, remove soil from site
- Construct footings up to DPC level
- Cast reinforced ground beams, including shuttering
Underground Drainage
Surface water drainage including soakaway, pipework, manhole and gully.
- Excavate and install 110mm underground drainage pipework
- Excavate and install 450mm uPVC manhole
- Excavate and install cellular soakaway
Structural Flooring
Structural floor slab with DPM and insulated screed ready for underfloor heating.
- Prepare levels and install structural flooring with DPM
- Install screed including 100mm insulation
Structural and Steelwork
Structural steel beams, goalpost frame and connections for the opening and rear glazing.
- Supply and install structural steel beam including preparation
- Install structural column up to 3m long
- Allow for steelwork connections
External Walls
Brick and block cavity walls to the new elevations with fire barriers and openings.
- Construct standard brick and block cavity walls
- Construct a wall or window opening with lintel and cavity closer
- Supply and install vertical and horizontal fire barriers
Roofing
New lean-to roof structure with covering, fascia, soffit and rainwater goods.
- Construct new roof including structure, insulation and covering
- Supply and install uPVC fascia and soffit boards
- Supply and install plastic rainwater goods
Joinery
Internal stud walls, doors, skirting and architraves throughout the extension.
- Construct internal timber stud walls
- Install internal door with frame and ironmongery
- Supply and install skirting boards and architraves
Plumbing and Heating
Underfloor heating, plumbing feeds, wastes and soil pipe for the kitchen and WC.
- Supply and install underfloor heating with standard thermostat
- Install hot and cold water feeds per point (first fix)
- Install 110mm soil pipe or toilet waste pipe per point
Electrics
First-fix and second-fix electrics including fuseboard, downlights, sockets and ventilation.
- Install small additional fuse board for the extension
- Install recessed LED downlights and pendant points
- Install smoke alarms and heat detectors
- Supply electrical certificate
Plastering
Plasterboard and skim to all new walls and ceilings throughout the extension.
- Plasterboard to new walls and ceilings
- Skim finish ready for decoration
Decorating
Full decoration to the new rooms in white emulsion and eggshell.
- Emulsion to walls and ceilings
- Eggshell to woodwork
Finishes
Floor and wall finishes including tiling and engineered wood flooring.
- Wall and floor tiling
- Engineered wood flooring
Fitting Out
Installation of kitchen units, appliances, sanitaryware and worktops.
- Fit kitchen units and worktops
- Install sanitaryware and appliances
Provisional Sums
Provisional allowances for items confirmed later, such as bi-folding doors and windows.
- Provisional allowance for bi-folding doors
- Provisional allowance for external windows
A worked breakdown
Single-storey rear extension, task by task
Here the phases meet real numbers: a sample of the itemised breakdown for a UK single-storey rear extension, each task with its quantity and price.
| Phase | Task | Qty | Price |
|---|---|---|---|
| Preliminaries | Supply and install scaffolding (per storey of elevation) | 15 LM | £1,710.00 |
| Demolition | Demolish external walls and clear the rubbish away | 15 M2 | £1,887.90 |
| Foundations and Footings | Excavate and cast trench foundations, remove soil from site | 9 M3 | £6,215.94 |
| Foundations and Footings | Construct footings up to DPC level | 15 LM | £1,972.95 |
| Underground Drainage | Excavate and install 110mm underground drainage pipework | 14 LM | £1,784.44 |
Illustrative sample. A full estimate itemises every task in every phase of the job. All prices exclude VAT.
Want this breakdown for your project?
Draft the full task breakdown yourself with BEX AI in minutes, or send us your drawings and we prepare it for you.
FAQ
Estimate tasks breakdown, answered
What is a construction estimate tasks breakdown?
It is an estimate split into its individual work items rather than a single price. Each phase of the build, from preliminaries to provisional sums, is broken into tasks, and each task carries its own quantity and cost, so the price is transparent and easy to check.
What are the main phases of a build estimate?
A BEX AI extension estimate runs preliminaries, demolition, foundations and footings, underground drainage, structural flooring, structural and steelwork, external walls, roofing, joinery, plumbing and heating, electrics, plastering, decorating, finishes, fitting out and provisional sums. Pricing in that order, from the ground up, keeps the estimate logical and stops tasks being missed.
Do I have to build the breakdown myself?
No. Send your drawings or project notes and our estimators prepare a fully itemised, branded PDF against live UK rates, or draft the breakdown yourself in minutes with BEX AI. A Basic Estimate is a flat £90; Detailed Estimates run £110 to £280 by project type. All prices exclude VAT.