Net income at Simpson Manufacturing fell $3.6 million from the same period last year to hit $15.9 million for the second quarter, the company announced today. Net sales at the company, which produces the Simpson Strong-Tie brand as well as other fasteners and construction products, grew 2% for the quarter ended June 30 to $181.7 million.

Net sales were buoyed by $9.7 million in sales from companies it acquired. The Pleasanton, Calif-based manufacturer saw sales to dealers increase during the second quarter, while sales to distributors remained flat and sales to home centers decreased.

Operating income for the quarter was $27.4 million, down from the $31.2 million reported a year ago. A 30% rise in research and development and engineering expenses, which topped out at $9 million, helped drive down operating income. The growth in research and development and engineering expenses included a $1.5 million increase in truss software development costs and personnel costs of $600,000.

Sales of wood construction products, which includes connectors, truss plates, fastening systems, fasteners, and shearwalls, represented 85% of total sales during the second quarter, down from 90% a year ago.

Sales of concrete construction products, including adhesives, chemicals, mechanical anchors, powder actuated tools and reinforcing fiber materials, increased to 15% of company sales during the quarter.