What is a construction Gantt chart, and how is it different from a programme of works?
A Gantt chart is a way of drawing a plan: tasks down the side, time along the top, and a bar for each task from its start to its finish. A programme of works is the plan itself, the construction programme for the job. In the UK the programme is nearly always drawn as a Gantt chart, so most people use the two terms for the same thing.
The words get muddled because of where they come from. US software and guides say "construction schedule" for what a UK contractor calls the programme. A UK schedule of works is different again: a list of the work to be done, often priced, with no dates on it. You price from the schedule of works, and you plan from the programme.
Who asks for it matters too. Under JCT's Standard Building Contract the main contractor provides a master programme (clause 2.9 in the 2024 edition). As a subcontractor you are usually asked for a programme for your package that fits into it. On NEC contracts the programme is part of the contract itself: it is submitted for acceptance and revised as the job goes on.
What goes on it: tasks, durations, dependencies, milestones and the critical path
- Tasks. The activities, at a level someone on site can act on. "Partitions" is a task. "Ground floor" is not.
- Durations, in working days. The programme above skips weekends and bank holidays. M&E first fix finishes on Thursday 25 March, but the ceilings cannot start until Tuesday 30 March, because Good Friday and Easter Monday sit in between.
- Dependencies. Which tasks wait for which. Most are finish-to-start: boarding has to finish before decoration starts. Some overlap: M&E first fix starts four working days after the partitions start, once there are walls to fix to.
- Milestones. Dates with no duration, such as handover, an access date from the main contractor, or a stage payment.
- The critical path. The chain of tasks where any delay moves the finish date. In the sample, 9 of the 10 tasks are critical. Doors, frames and joinery has 8 working days of float, so it can slip that far without moving handover.
Before any of that comes the work breakdown structure, the list of what has to be done. On a subcontract package it is usually the line items in your quote, grouped by trade or by area.
Programme levels: L1 to L4
- Level 1: a one-page summary of key dates.
- Level 2: the main phases or areas of the job.
- Level 3: the detailed programme the job is run from, with every activity and link. A subcontractor's package programme, like the sample, is usually Level 3.
- Level 4: short-term working detail for one trade or area, such as a 2–4 week lookahead.
How to build one for your next job: Excel or a proper tool
For a first programme, Excel is fine. The standard method takes ten minutes:
- List each task with a start date and a duration in days.
- Insert a stacked bar chart from the task, start and duration columns.
- Format the start-date series with no fill, so only the duration bars show.
- Reverse the category order so the first task sits at the top, and set the date axis to start on day one of the job.
Where it breaks is the second week. Excel does not know that decoration waits for second fix, so when second fix slips you move every following bar by hand. It does not know about bank holidays unless you build them in with WORKDAY formulas and a holiday list. And the costs live in another sheet, so the programme and the price drift apart. If you already estimate in a spreadsheet, you will know the pattern from where estimating spreadsheets break.
A proper tool stores the links and recalculates the dates for you. That is the whole difference: in the sample, move the partitions back a week and everything after them moves too, including the stage payments.
Put money on the programme: cost, charge and margin per task
Most construction Gantt charts stop at dates. Put two more numbers on each task, what it costs you and what you charge for it, and the programme starts answering commercial questions.
In the sample, the job makes 18.23% overall, but not evenly. The subcontracted M&E runs at 10.66% and 10.50%, while decoration runs at 28.53%. That tells you where a delay hurts most, which variations are worth chasing, and whether the package still works if the M&E price comes in high. Margin here is profit as a share of the charge; if you are not sure how that differs from markup, see margin vs markup.
A planned margin is only the starting point. Once the job is running, compare cost and value month by month with a cost value reconciliation.
Tie stage payments to milestones, so cash comes in as work completes
Under the Construction Act, a party to a construction contract is entitled to payment by instalments, stage payments or other periodic payments, unless the work is agreed to take less than 45 days (section 109). You and your client can agree the stages and when they fall. Where the contract does not set out the payment terms, the Scheme for Construction Contracts fills the gaps.
Put each stage on the programme as a milestone tied to the task it waits for. In the sample, 4 stages of 10%, 25%, 30% and 35% follow the work. At Stage 3: ceilings and M&E second fix complete, on 14 April, the job has spent £123,000.00 and earned £120,835.00, so it is running on your money. That is before payment terms, which push the cash later still.
Because the payments are tied to tasks, a slip moves them. If the partitions run a week late, stage 2 moves a week, and so does the cash.
This is general information, not legal advice. Check the payment terms in your own contract.
Use the programme to win the job
A short programme attached to a quote or tender does two jobs. It shows the client how you will run their work, in what order and how long it takes, before they have to take your word for it. And it puts your assumptions on record: access dates, when you need drawings or decisions, and lead times on long-lead items. If those change after you have won the job, the tender programme shows what you priced against.
The best time to draw it is while you price, from the same line items. A construction estimating tool that already holds the quantities and labour can turn them into tasks and durations, so the programme and the quote agree from day one.
Keep it live: baseline vs actual and the 2–4 week lookahead
Save the programme you start with as the baseline. Each week, record what actually started and finished, and let the rest move. The gap between the baseline and the current programme is your slippage, and the record of why it moved is what supports an extension of time later.
The Society of Construction Law's Delay and Disruption Protocol sets out good practice: update the programme at least monthly, keep every update rather than overwriting it, and work from short lookaheads on site. On site, nobody reads ten weeks of bars. They read the next two to four weeks: what starts, what has to be ready for it, and who needs to be there.
Construction programme software compared
Prices and free-plan limits below were checked on 9 October 2026 and change often, so check the supplier's own pricing page before you decide.