THE construction industry's positive response to the international standards organisation (ISO) requirement set by the Housing Authority has been applauded by the architects, surveyors and planners constituency's legislator, Mr Edward Ho Sing-tin. ''You're probably the largest single group of ISO-certified construction companies anywhere in the world,'' Mr Ho said yesterday at a reception to celebrate the response. Thirty companies, including builders, concrete producers, foundation contractors and material suppliers, have attained the ISO 9000 certification - from this month a prerequisite for undertaking Housing Authority projects. Mr Ho said the requirement for the authority's contractors to have the formal quality management system was a logical step in its long-term drive for better public housing. ''It followed earlier successful measures to encourage greater mechanisation of the building process, and a steady move towards greater standardisation of components,'' he said. The authority had taken a gamble in calling for ISO 9000 certification three years ago, he conceded. ''But like all successful punters we had studied the form book and we were confident the industry would rise to the challenge,'' he said. ''The Hongkong construction industry has always shown itself well able to rise to formidable challenges.'' Contractors and concrete suppliers certified to ISO 9000: Able-Pentad Joint Venture, Chee Cheung Hing, Cheung Kee Fung Cheung Construction, China State Construction Engineering Corp, Franki Contractors and B+B Asia Technical Services, Gammon Construction, Glorious Concrete, Hongkong Concrete, Hsin Chong Construction, Hung Wan Construction, International Precast Systems, International Tak Cheung General Contractors, Ken On Concrete, K Wah Concrete, Kwan Lee Construction, Leighton Contractors (Asia), Ngo Kee Construction, Pioneer Concrete, Quon Hing Concrete, Ready Mixed Concrete, Redland Concrete, Sogea, Shui On Building Contractors, Shun Shing Construction & Engineering, Sung Foo Kee, S Y Engineering, Wan Hin, Woon Lee Construction, W R Grace, and Yau Lee Construction. But the authority felt that more should be done, and was setting programmes for ISO certification for building services and foundation contractors. ''We're encouraging the works branch to advance their own deadlines for the use of quality-assured companies,'' he said. The authority's home ownership committee resolved last month that future developers of private sector participation schemes would be required to use certified companies.