The verdict in three sentences
For a London construction manager, custom site management software costs between 45,000 and 130,000 GBP in 2026, versus 35 to 100 GBP/user/month for a vertical licence. Custom pays off once you exceed 15 to 20 field users or when your time-logging, progress and invoicing process no longer fits a standard tool. The real metric is not the licence price: it is the margin point gained per site when planning slippage drops by 25 %.
Custom or licence: the real calculation in London
Vertical SaaS editors deploy fast but bill per user, every month, forever. Custom is an upfront investment you own. Here are 2026 orders of magnitude for a mid-sized London main contractor.
| Criterion | Vertical licence | Custom by Kolonell |
|---|---|---|
| Upfront cost | 0 to 5,000 GBP (setup) | 45,000 to 130,000 GBP |
| Recurring cost | 35 to 100 GBP/user/month | Maintenance 15 %/year |
| Time to go live | 2 to 6 weeks | 4 to 7 months |
| Fit to your process | Low to medium | Total |
| Accounting/payroll integration | Often a paid add-on | Native, quoted |
| Code ownership | No | Yes |
| Cost at 30 users over 5 years | 63,000 to 180,000 GBP | 80,000 to 160,000 GBP |
At 30 field users over five years, a licence at 70 GBP/user/month totals 126,000 GBP cumulatively, and you never own the tool. Custom development at 90,000 GBP plus 13,500 GBP/year maintenance totals 157,500 GBP over the same period, but leaves you an asset you control and that fits your process 100 %.
What the software must cover
Useful site software in 2026 is more than a schedule. Here are the core modules and their measured impact across a portfolio of sites.
| Module | Key function | Measured impact |
|---|---|---|
| Progress tracking | Valuations, percent complete, planned vs actual curve | -25 % planning slippage |
| Field time logging | Hours per worker, per task, geolocated | -30 % payroll errors |
| Timestamped photos | Proof of work, snags, disputes | -40 % handover disputes |
| Materials management | Orders, deliveries, on-site stock | -15 % material losses |
| Interim invoicing | Automated interim valuations | +8 days of cash flow |
| Manager dashboard | Margin per site in real time | Faster decisions |
The module that pays back fastest is almost always progress tracking coupled with time logging: that is where margin leaks, between misallocated hours and late valuations.
Mini case study
James, construction manager at a 45-employee main contractor in London, runs 6 concurrent sites for annual revenue of 10.5 M GBP. His planning slippage costs roughly 3 % of revenue in penalties and non-billable hours, i.e. 315,000 GBP/year. He invests 90,000 GBP in custom software plus 13,500 GBP/year maintenance.
By cutting slippage by 25 %, he recovers 78,750 GBP/year. Payback is reached in 15 months, maintenance included. On top of that come cash-flow gains from faster valuations and fewer payroll errors. Over five years, cumulative net gain exceeds 290,000 GBP.
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FAQ
How much does custom site management software cost in London in 2026?
Budget 45,000 to 130,000 GBP depending on modules and integrations. A core scope (progress, time logging, photos, interim invoicing) sits around 70,000 to 90,000 GBP.
Custom or vertical licence: which should I pick?
Below 15 users, the licence is often cheaper. Above 20 field users or with specific processes, custom pays off over 4 to 5 years and makes you the owner of the tool.
How long does deployment take?
Budget 4 to 7 months from scoping to production, with a first usable version on site within 2 to 3 months. Sprint-based delivery lets you test early on a real site.
Does the software work offline on site?
Yes, offline mode is essential: time logs and photos sync as soon as the network returns. It is a non-negotiable requirement for real site use.
Can we integrate our accounting software?
Yes, integration with your accounting or payroll (hours and valuations export) is included in the quote. That is precisely the custom advantage over verticals that charge for these connectors.
Let's scope your project. Tell us your number of sites, field users and the accounting/payroll integrations you need, and we will price a core scope around 70,000 to 90,000 GBP. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
