Government plans to tighten up the Building Regulation include a key proposal to force through significant energy performance improvements to the rest of the home when an extension is built.
House building lobby group, the Modern Masonry Alliance dubbed the proposal an extension tax.
Mike Leonard, director of the Alliance, said: “I believe this will be a barrier to people trying to improve their properties.
“It will dissuade them from going ahead on both the grounds of cost and the extra complexity of getting the job done.
“The only outcome of this will be that fewer extensions get built, which nobody wants to see.”
The ‘consequential improvements’ plan was highlighted in the Government Part L consultation process, which closes on 22 March.
This lays out plan to force homeowners building an extension to set aside an extra 10% of the cost for improvements to the rest of the home.
Leonard added: “If the homeowners decided to apply for Green Deal funding to cover the additional costs they would then open themselves up to the requirement to use a specially approved supplier.
“This is likely to result in the need to include one or more third party contractors in addition to their tried and tested local builder.
“Alternatively homeowners may entrust the whole project to Green Deal providers like B&Q and British Gas and in doing so cut out the SME altogether.”
He said that the Government needed to offer a proper incentive to encourage more homeowners to improve their property not raise fresh barriers.
“I want to see the Government top-slice some of the £1 billion a year eco-fund to offer a range of free and simple energy efficient upgrades to those who undertake substantial home improvement work.”
“It's a simpler approach that will achieve the same positive outcome - an improved and more energy efficient housing stock.”