SIG, the supplier of insulation, roofing, commercial interiors and construction products, posted a fall in sales during the first quarter of the year due to foreign exchange movements but said the UK construction market remains robust.Like-for-like sales were flat during the quarter and sales from continuing operations fell 3.6%, hurt by a weak euro.In the UK, sales rose 2.8% but the roofing division business slowed in March and April due to uncertainty ahead of the general election. Sales in Europe declined 3%, but SIG made three infill acquisitions with activities in the air handling, interiors and insulation sectors. It also acquired four infillins in the UK roofing sector.The group said in a statement that against the demanding comparative period a year ago, and in light of the continuing variable market conditions as well as adverse foreign exchange movements, it believed that its reported results "will be more weighted towards the second half than previously anticipated".Panmure analysts gave a 'buy' recommendation as they believe that, despite forecasting revenues and profits "likely to be slightly more weighted" during the second half, "the overall picture remains unchanged", expecting profits before tax up 8.3% in 2015 and 9.8% in 2016.Shares fell 2.37% to 206.2p on Thursday at 14:23.