Builders fear waste plans will backfire and harm industry
Proposals for all building projects in Wales to include plans on how waste will be disposed of could mean more fly-tipping, the Federation of Master Builders (FMB) warns.
It fears Welsh ministers' plans to reduce building waste going to landfill could backfire and hit the industry.
Similar rules in England apply to larger projects but in Wales they could even include house extensions.
The Welsh government said it had worked with the FMB to minimise the burden.
A Welsh government consultation on site waste management plans (SWMPs) closed on 25 April.
The new rules are proposed in order to help the Welsh government's target of increasing construction waste reused and recycled to a minimum of 90% by 2020.
Clients and their contractors would have to submit the plans to local councils, explaining how they will dispose of waste from building sites.
Every building project in England worth more than £300,000 has needed an SWMP since April 2008.
But the Welsh government wants SWMPs to apply to all work that needs planning permission or which must comply with building regulations.
That would include big commercial and residential schemes but could also include extending a house or replacing windows.
There would be some exceptions, for example for the nuclear power industry or for small jobs by some certified tradesmen.
The Welsh government says the UK government policy of only insisting on the plans for big projects in England "has a number of weaknesses".
An SWMP would have to be signed off by a local council and responsibility for it would be split between the client and contractors.
The fee to submit an SWMP for the smallest projects would be between £50 and £100, the Welsh government proposes.
Anyone convicted of breaking an SWMP could face fines of up to £50,000.
But the FMB said it feared the plans could backfire and drive the industry "further into the doldrums".
One developer said smaller builders would be worst hit and said the rules should apply to only larger projects.
FMB Wales director Richard Jenkins said the regulations would fuel the black economy.
They have been designed in part to tackle fly-tipping, but Mr Jenkins said they risked backfiring and making the problem worse.
Cowboy builders could under-cut reputable contractors by telling clients to ignore the regulations and dumping the waste illegally, he said.
"It's counter-productive," he said.
"It's going to drive the industry further into the doldrums."
Kevin Ireland, who runs Delta Properties in Cardiff, said: "It's another cost which will be borne by proper contractors and something the black market economy won't do."
Chris Wynne, the managing director of Wynne Construction based in Denbighshire, said the new waste plans should only be for developments worth over £300,000.
"The problem will be with smaller builders, it's an added financial burden," he said.
"At the moment larger jobs absorb these costs but it is going to add an extra layer (of cost) which will have to be passed on to customers."
Conservative ministers in the UK government have accused the Labour administration in Cardiff of "destroying the housing market".
It follows complaints by the construction sector about the burden of other Welsh regulations, including plans to install sprinklers in all new homes.
UK Communities Secretary Eric Pickles said the industry in Wales faced "extra bureaucracy, meaning fewer new homes and first time buyers".
"The Labour Party is destroying the housing market in Wales with its extra regulation and red tape," he said.
A Welsh government spokesperson said: "We have worked with industry representatives, including the Federation of Master Builders, to minimise the burden of the proposed regulations on the building industry and have set out how any additional planning can be off-set by significant cost savings resulting from adopting more sustainable waste practices.
"We have consulted on the scope, content and enforcement of the proposed regulations and will fully consider all the responses received over the past 12 weeks before developing the regulations further."