Cash flow basics for a building firm that wants to sleep at night

Building firms rarely die of no work. They die of no cash, often in a busy month, often while technically profitable on paper. If that sentence sounds impossible, this article is for you. Cash and profit are different animals, and in construction the gap between them is wide enough to swallow a firm whole.

Profit is an opinion, cash is a fact

Profit is what the spreadsheet says you will have earned when everything is invoiced, paid and settled. Cash is what is in the bank on Friday when wages go out. A £70,000 job with £12,000 profit in it can still sink you if you spend £30,000 on materials and labour before the client's first payment lands. You were profitable the whole time. You were also, for six weeks, a lender: financing your client's project from your own account.

That is the structural truth of building work. You buy the materials, you pay the wages, and the money comes back later, in lumps, sometimes late. Managing a building firm is largely managing that gap.

Know your job's cash curve

Every job has a cash curve: cumulative money out versus cumulative money in, week by week. Money out is smooth and relentless: wages every week, materials in bursts. Money in is lumpy: a deposit, then stage payments. The area where the out-line sits above the in-line is money you are lending the job. Two overlapping jobs both in their deep-lending phase at once is how a busy firm runs out of cash.

Stage payments: design the curve at quote time

The cash curve is not weather. You design it, and you design it in the quote, before anyone signs anything. The principles:

• A deposit that covers mobilisation. Enough to cover initial materials and the first stretch of labour, so you are never lending from week one.
• Stages tied to visible milestones. Footings poured, wallplate on, watertight, first fix done, completion. Visible events do not get argued about; percentages of "progress" do.
• Frequent beats large. Five smaller stages beat two big ones: each payment is easier for the client to release and each gap you finance is shorter.
• Big-ticket materials paid when ordered. Steels, glazing, kitchens: the client pays when you order, not when you install. You should not be warehousing £15,000 of their windows on your overdraft.
• Final balance small but real. Keep enough back-end for the client to feel protected, not enough to hurt you if the last conversation drags. Retentions have their own rules, covered in retentions and snagging: protecting the last five percent.

An itemised quote makes all of this easier to agree, because the stages map to sections of the bill the client can already see. When the quote itself is a measured bill of quantities, the kind QS Quoter builds at your own rates through a structured, reviewable workflow, the payment schedule almost writes itself, and it looks reasoned rather than plucked. The full playbook is in stage payments that protect your cash flow.

Treat that as a template to adapt, not gospel: the right split depends on where your big costs land in the programme.

The weekly habit that replaces worry

Grand cash forecasting systems die in busy firms. A thirteen-week look-ahead on one page survives, and it is enough. Every Friday, fifteen minutes:

1. Bank balance today.
2. Money in, by week, for thirteen weeks: stage payments due, dated realistically, not optimistically.
3. Money out, by week: wages, subbies, materials, VAT quarter, van finance, the lot.
4. Running balance along the row. Any week that goes red is a problem you now know about two months early, while it is still cheap to fix.

A red week ten weeks out has easy fixes: pull a stage payment forward, delay a material order, chase an invoice, shift a start date. The same red week discovered on the Thursday it happens has only expensive fixes. The whole value of the habit is buying yourself time.

Slow payers and the pipeline gap

Two more leaks worth naming. First, slow payers: invoice the moment the milestone is hit, not at month end, and chase on day one overdue, politely and every few days. The firms that get paid on time are simply the ones that visibly notice. Second, the pipeline gap: cash crises often start three months earlier as a quoting gap, when a busy firm stops sending quotes and the next jobs are not lined up when the current ones finish. Cash flow planning and capacity planning are the same discipline viewed from two angles: keep quoting even in flat-out months.

The blunt summary

Cash flow in a building firm comes down to four habits: design the payment schedule at quote time so the client funds their own job, keep big material costs off your overdraft, run a thirteen-week look-ahead every Friday, and ring-fence the VAT. None of it is clever and all of it is learnable in a month. The reward is not just solvency. It is the version of this business where Sunday evenings are quiet.