The Riverside Company, a global private investor focused on the smaller end of the middle market, completed the investment in Sir Grout, a provider of grout, tile and other hard surface restoration services for residential and commercial customers. Financial terms were not disclosed. "We’re thrilled to add another company to our Threshold Brands platform. With Sir Grout’s expansive knowledge in hard surface restoration services, we believe that the company’s high-quality materials and top-level service will have unparalleled benefits to the platform," Loren Schlachet, Riverside Managing Partner.