How Do I Know If My Projects Are Actually Making Money? (Job Costing)

Job Costing & Overhead Allocation:

Published 25 August 2026

A practical guide for contractors and construction business owners

You win the job. You do the work. You send the invoice.

But at the end of the month, when you look at your bank account, something does not add up. The jobs are coming in. The team is busy. Yet the profit is not where it should be.

This is one of the most common — and most frustrating — experiences in construction. And in most cases, the root cause is the same: you do not have a clear picture of what each job is actually costing you.

Job costing is the process of tracking every pound spent on a specific project — labour, materials, plant, subcontractors, and a fair share of your overhead costs. Done properly, it tells you exactly where you made money and where you lost it.

Done poorly — or not at all — you are essentially running your business blind.

Why Most Contractors Struggle With Job Costing

The problem is rarely effort. Most contractors work hard and care about doing a good job. The problem is system.

Without a structured approach to tracking costs, a few things tend to happen:

• Materials get purchased across multiple accounts and suppliers, making it hard to tie costs back to a specific job

• Labour hours are tracked loosely or not at all, making it impossible to know your true labour cost per project

• Overhead costs like insurance, vehicle expenses, and office rent are treated as general business costs rather than being allocated across individual jobs

• Unexpected costs — a price increase from a supplier, additional labour to fix a problem — get absorbed without being properly recorded

The result is that you finish a job thinking you made 15% margin and discover later — if you discover it at all — that the real number was closer to 4%. Or worse.

Step One: Break Every Job Into Cost Categories

The foundation of accurate job costing is a consistent set of cost categories. Every expense on every job should be assigned to one of these buckets:

1. Direct Labour

The wages or subcontractor costs directly tied to working on that specific job. This includes your own time if you are working on site.

2. Materials

Every material purchased for that job — timber, fixings, plumbing supplies, electrical components. Every delivery note and every invoice should reference the job number.

3. Plant and Equipment

Hired plant, tool consumables, fuel used on site, and any equipment costs directly associated with the project.

4. Subcontractors

Any specialist trades or labour-only subcontractors brought in for that job. These should be tracked separately from your own labour costs.

5. Overhead Allocation

A proportional share of your business running costs — more on this below.

Setting up these categories in your accounting software or job management system from day one means every cost has a home. Nothing gets lost in a general account and forgotten about.

Step Two: Track Labour Accurately

Labour is typically the largest cost on most construction projects — and it is also the one that is most commonly tracked poorly.

To know your true labour cost per job, you need to know:

• Who worked on each job and for how many hours

• The true cost of that labour — not just the hourly rate, but the total employer cost including National Insurance contributions, holiday pay, and any other employment costs

A simple daily timesheet — even a paper one or a basic app — gives you this information. The key is consistency. Every person on your team records their hours against a job number every day.

If you use subcontractors on a labour-only basis, the same principle applies. Their invoices should reference the job they worked on so the cost is captured accurately.

Step Three: Allocate Overhead Costs Across Your Projects

This is the step that most contractors miss — and it is one of the most important.

Your overhead costs are the expenses that keep your business running regardless of how many jobs you have on. These typically include:

• Office rent or home office costs

• Business insurance and professional indemnity

• Vehicle costs not directly tied to a single job

• Accountancy and professional fees

• Software subscriptions and office supplies

• Your own salary or drawings if you are not working on site

These costs are real. They need to be recovered through your projects. If you are not allocating them to your jobs, you are not getting a true picture of profitability — and you are almost certainly underpricing your work.

How to Allocate Overhead: A Step-by-Step Approach

Step 1: Calculate your total annual overhead

Add up every overhead cost your business incurs in a year. Be thorough. Include everything that is not a direct project cost.

Let us say your total annual overhead is £60,000.

Step 2: Calculate your total annual direct labour hours

Estimate how many hours your team will work on billable projects across the year. If you have two full-time site workers each working 45 weeks at 40 hours per week, that is:

2 × 45 × 40 = 3,600 hours

Step 3: Calculate your overhead recovery rate

Divide your total overhead by your total labour hours:

£60,000 ÷ 3,600 hours = £16.67 per labour hour

This is your overhead recovery rate. For every hour your team works on a project, you need to recover £16.67 in overhead on top of their direct labour cost.

Step 4: Apply the rate to each job

When you cost a job, multiply the estimated labour hours by your overhead recovery rate and add it to your project costs.

For example, if a job requires 200 labour hours:

200 × £16.67 = £3,334 overhead to recover

This amount gets added to your direct labour, materials, plant, and subcontractor costs before you calculate your margin.

Step 5: Review and adjust regularly

Your overhead rate is not fixed forever. Review it at least every six months. If your overhead costs increase or your workload changes significantly, your recovery rate needs to be updated to reflect reality.

Step Four: Deal With Unexpected Cost Increases

Even with the best systems in place, unexpected costs happen. A supplier increases their price mid-project. A phase takes longer than planned. Additional materials are needed due to a design change.

The key is to capture these costs immediately rather than hoping they will wash out.

Practical steps when unexpected costs arise:

• Record the cost against the job straight away — do not let it sit in a general account

• Quantify the impact on your margin — know immediately what the overrun means for the job's profitability

• Issue a variation where appropriate — if the additional cost is due to a client-driven change, raise a variation order promptly and get it signed before you do the work

• Use it to improve your estimating — every unexpected cost is information. Review it after the job and ask whether your original estimate was realistic or whether your pricing needs to change

Step Five: Review Every Job After Completion

A job costing system only delivers its full value if you actually use the data it produces.

After every project, run a simple post-job review:

• What did we estimate versus what did we actually spend? — broken down by category

• Where did we lose money? — labour overruns, material waste, unexpected costs

• Where did we perform well? — areas where your estimate was accurate or you came in under budget

• What would we do differently next time? — adjust your estimating approach, your purchasing process, or your site management

Over time, this review process improves your estimating accuracy, tightens your cost control, and builds a clear picture of which types of work are most profitable for your business.

The Tools That Make This Easier

You do not need expensive software to run a good job costing system. What you need is consistency.

Some options worth considering:

• Xero or QuickBooks with job tracking — both allow you to assign costs to specific projects and run profitability reports

• Tradify, Buildertrend, or SimPRO — purpose-built for construction, with job costing, timesheets, and purchase order tracking built in

• A simple spreadsheet — if you are just starting out, a well-structured spreadsheet can do the job while you build the habit

The best system is the one your team will actually use. Start simple, be consistent, and upgrade as your business grows.

A Final Thought

Knowing whether your projects are making money is not a luxury. It is the foundation of running a sustainable construction business.

Without accurate job costing, you are pricing on gut feel, managing costs by guesswork, and finding out whether a job was profitable long after it is too late to do anything about it.

With it, you have the information you need to price confidently, spot problems early, and make decisions based on real numbers rather than hope.

The good news is that it does not have to be complicated. It just has to be consistent.

This article is for general information purposes only and does not constitute financial or legal advice. Speak to a qualified accountant for advice specific to your business.

Are Your Jobs Making the Money You Think They Are?

If you are not sure whether your job costing is giving you an accurate picture, it is worth having a conversation.

At B.R. Pusser & Co, we work with construction and trades businesses to set up practical financial systems that give you real visibility over your project profitability.

We can help you:

• Set up job costing in your accounting software

• Calculate your overhead recovery rate

• Understand which jobs and which types of work are most profitable

📩 Send us a message or book a free call with Brian today — no obligation, just a straightforward conversation about your numbers.