The latest £30 rise has been imposed with immediate effect and means that steel prices have risen by £260 a tonne since last July.
The speed of the rise is unprecedented and has been blamed on sharp rises in raw material costs, quotas and scrap availability.
Rebar prices are also being pushed through the roof in the concrete frame sector.
Recent spate of increases
£/ tonne rise: July +£30; August +£30; Nov +£40, Dec +£80; Jan +£50; March +£30
One small steel fabricator told the Enquirer: “This is starting to cripple the industry. We’ve seen a £20,000 increase on one job due to start in April.
“There are also concerns about supply lead times. We are seeing lead time for steel decking move out to 12 weeks.”
Another firm added: “We’ve not seen anything like this since 2004. There is a growing realisation that this is not the last of it.
“Many firms operating on thin margins will not have the resources to ride this out.”