Turnover at the Portakabin-owned business almost halved to £72m in 2025, down from £140m in the previous year.
Darwin recorded a £5m operating loss, compared with an £8.6m operating profit a year earlier, while its pre-tax performance swung from a £9.2m profit to a £3.2m loss.
Directors attributed the reversal to several large permanent modular healthcare projects that encountered operational delivery problems and cost overruns.
The setback has led Darwin to increase its focus on smaller and less complex modular buildings, as well as the hire market, as part of the wider Portakabin group.
The Telford-based business specialises in offsite healthcare construction and was acquired by Portakabin in 2023 as the modular construction group sought to expand its presence in the NHS market.
Average employee numbers fell to 174 during the year, compared with 200 previously, while the contracts workforce declined from 172 to 145.
Directors said the business would continue to focus commercially on the UK healthcare sector, while concentrating on smaller modular sales and hired space.
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