A change to new rules capping the size of amenities and green features at 10 per cent of gross floor area will now effectively give developers a six-month grace period, revised guidelines issued yesterday show. Developers will also be allowed to keep walls that take up internal floor space thicker than 15cm, according to fine-tuned technical guidelines the Buildings Department issued to the construction industry. Initially, any plans submitted to the Buildings Department for approval on or after April 1 would have to follow the stricter new rules. Yesterday, however, officials added the guidelines that if a developer submitted a fresh plan before that date and the application was rejected, the developer could submit it again within six months and the project could still follow the old rules. This means that if a developer hands in a building plan in March and officials, who usually take two months to vet applications, turn it down in May, the developer can still gain from the old concessions if it resubmits it by November. The Democratic Party's spokesman on housing affairs, Lee Wing-tat, said: 'This exemption obviously does the developer a favour. Developers can rush to submit building plans for their sites now. Even if they are rejected, they have already secured the old advantages.' The guidelines - a fine-tuned version of the measures announced by Chief Executive Donald Tsang Yam-kuen in his policy address in October - aim to control the scale of residential developments by capping the amount of floor area that can be given to amenities and green features. Facilities and features such as balconies and clubhouses should not exceed 10 per cent of the gross floor area of a development. The measures were subsequently put to consultation within professional bodies and the Real Estate Developers Association. Roy Tam Hoi-pong, of Green Sense, said he was disappointed about the six-month grace period for some projects. The Development Bureau said the arrangement was aimed at addressing concerns that some projects might be rejected for 'unforeseeable technical reasons', and it would only apply to developers that had a 'realistic prospect of owning the land'. The Real Estate Developers Association said it was unable to comment on the guidelines yet as it would need time to study them. In addition, the rule reducing the thickness of prefabricated external walls of a flat from 30cm to 15cm was revised to allow decorative finishes or stone panels of 7.5cm. This means a flat buyer could still get a 22cm-thick, unusable wall within the saleable area of the flat. The guidelines also remove from the 10 per cent cap items that are considered environmentally friendly and do not greatly inflate building bulk, including rainwater recycling systems, noise barriers and covered walkways in open spaces shielding residents from the sun and rain.