Lincoln Magistrates’ Court heard the injured men were working for Persimmon on a development in Ploughman’s Lane when the incident happened on 4 April 2012.
They were about to start work on a scaffold platform six metres from the ground, which had been loaded with materials.
Just as they began the scaffold collapsed and they fell around two metres on to a platform below.
One, a 62-year-old from Rossington, South Yorkshire, broke his left foot. He was unable to work for nine weeks.
The second, 29, also of Rossington, bruised his neck and twisted his knee. He missed one day of work.
An HSE investigation found The Cathedral Scaffold Company Ltd had constructed the scaffold to bridge a narrow gap between the gable ends of two neighbouring properties.
But the company did not build it to a recognised design, which would have incorporated standards to transfer loads to the ground.
They wrongly believed they could not fit them and a four board-wide working platform, as required by Persimmon, into the gap.
Instead they used a non-standard configuration of scaffolding but failed to carry out strength and stability calculations to ensure it was fit for purpose.
The company issued a Handing Over certificate to Persimmon, setting out restrictions on the use of the scaffold.
This identified it as a general purpose scaffold capable of supporting a specified distributed weight load, but because no strength or stability calculations were undertaken by either defendant, this distributed load could not be guaranteed.
Persimmon subsequently overloaded the platform, causing it to collapse.
HSE found the weight of just one pack of dry blocks distributed evenly over the platform would have taken it over the load limit – even without the men, tools or mortar on the platform.
Persimmon Homes Ltd, of Fulford, York, pleaded guilty to breaching safety regulations and was fined £8,000 and ordered to pay £10,426 costs.
The Cathedral Scaffold Company Ltd, of Dixon Way, Lincoln, pleaded guilty to breaching safety regulations and was fined £4,000 with costs of £5,500.
Speaking after the hearing, HSE inspector Linda-Jane Rigby said: “Unless a scaffold is a basic configuration described in recognised guidance it should be designed by calculation, by a competent person, to ensure it will have adequate strength and suitability.
“The design information should describe the sequence and methods to be adopted when erecting, dismantling and altering the scaffold. That did not happen in this case.
“Persimmon accepted handover of the scaffold and subsequently overloaded it, causing it to collapse.”
