Davis Langdon predicts up to 5% extra costs due to new Part L regs

Part L could add 5% to the cost of building projects according to research by Davis Langdon and Hoare Lea.

This is more than double the 2% rise set out in the ODPM's Regulatory Impact Assessment (RIA). Whereas the 2% refers to the cost of minimum compliance with the new version of Part L, in reality firms will go further.

Simon Rawlinson, partner at Davis Langdon, told a building regulations seminar at the RICS: "I'd be careful about just taking this 2% and adding it to the cost plan. These costs are taken across a huge range of building types so one would expect them to be fairly generalised."

He added that Part L could add between 2% and 5% to the cost of buildings.

However, an ODPM spokesperson said he hadn't seen any evidence for the 5% estimate.

"Over the lifetime of new buildings the financial as well as environmental benefits from carbon savings vastly outweigh the extra costs, which can often be passed on to the client," he said.

The ODPM RIA predicted Part L would add 1.9% to the cost of public buildings and 1.6% on industrial buildings.

Rawlinson said that on a high performance 100% glazed building, the extra cost of complying could be £61-£97/m2, or 3.2-5.1%.

Gleeds backed up the 5% top estimate in its own seminar last week. However, its figure for a 12,000m2 glass-fronted building came in slightly lower than Davis Langdon's: 2.39-3.8% more.

Rawlinson also said he was not confident in the government's SBEM technology for measuring buildings' Part L compliance, because its emissions targets for air-conditioned buildings were too tough.

"At the moment we don't have a lot of faith that this gives the right answers," he said.

In the past five years we’ve got good at getting disabled people into buildings, and done nothing to help getting them out

Anna Thompson, vice chairman, RICS Building Control Board

David Smith, RICS business development manager, said issuing the Part L Approved Document just two weeks before the regulation came into force had caused "immense confusion".

He warned the industry should only trust the version of Part L on the ODPM website after the recall of documents published by RIBA and The Stationery Office.

He predicted further troubles with the updated regulation. There could be problems with homeowners doing their own DIY because it may not conform to the tough new standards.

"Five years hence this is going to be a massive problem," said Smith.

He added that he expected pressure testing to cause problems. He said that if you were drylining the walls in a garage to convert it into a habitable room, for example, pressure testing meant that elements such as the roof would also have to comply.

Currently the average air leakage of dwellings is 11m3/h/m2 at 50Pa. Tighter controls under the new Part L mean the maximum leakage should be 10m3/h/m2 at 50Pa. To fit with the new Part L there have been changes to Part F, dealing with ventilation. The least a building can leak is now 3m3/h/m2 at 50Pa.

Anna Thompson, RICS Building Control Board vice chairman, also highlighted changes to Part B, dealing with fire safety, at the meeting.

Thompson said she expected two versions of Part B, one for dwellings up to four storeys high and another to deal with fire risks in taller buildings. These could include more focus on fire prevention and risk assessment, and more inclusive design to improve safety for disabled people.

"In the past five years we've got good at getting disabled people into buildings, and done nothing to help getting them out," she said.

Technical changes could include greater use of residential sprinklers, smoke alarms in main bedrooms and design changes in larger buildings like warehouses to stop fires spreading.