"After an excellent start, demand from all segments of our core UK market has remained strong," said the company.
Order intake has remained consistent with the normal seasonal pattern and yet to show any signs of weakening following the EU referendum, the group reported.
Revenue for the first half of 2016 was £223.3m, up 31% from last year. Excluding acquisitions, the revenue was 8.1% ahead of last year.
Underlying operating profit grew 47% to £37.7m, with profit before tax up 29% to £29.9m. The group's operating margin was 16.9% for the half-year, compared to 15.1% for the same period in 2015.
Chief executive David Hall said: "We have delivered another record performance in the first half continuing the strong momentum from last year. Our strategic focus on the structural growth opportunities, together with the acquisition of our Nuaire ventilation business has accelerated our growth.
"Despite the uncertain economic backdrop, the long-term structural drivers of our business remain strong, our balanced business model means that we are not overly exposed to any particular sector and the nature of the Group's production processes enables us to adapt and flex quickly to changes in demand. The Board is confident that the cash generative characteristics of the business and a commitment to remain agile will enable the Group to continue to develop and outperform, whatever the market conditions."
The Nuaire acquisition has been performing well, reported the group, with some early success in specification of Nuaire systems with Polypipe duct.
The first delivery from the manufacturing plant in Dubai was made during July.
The group also noted encouraging comments from the UK government recognising the need to provide stimulus for construction.