A woman on the receiving end of a six-figure compensation claim after a Polish builder fell off a ladder while repairing her roof will not have to pay a penny, the High Court has ruled.

Nadia Isaacs of Hampstead, north London, hired a building firm which "may have deserved the epithet of a cowboy operator", the court heard.

When labourer Tomasz Kmiecic, 31, suffered permanently disabling injuries while working on her home, in June 2006, the scene was set for a legal struggle which has been hanging over Mrs Isaacs's head ever since.

Mr Kmiecic injured his elbow, hip and thigh when a ladder that was too short toppled as he climbed up to Mrs Isaacs's leaky garage roof. His injuries were so serious that he can no longer work as a carpenter and general builder.

His lawyers claimed that, as it was her ladder, Mrs Isaacs was legally responsible, even though she had no idea it had happened until three months later.

But Mrs Justice Swift ruled that the real culprit was the builder for whom Mr Kmiecic was working as a casual labourer, on a rate of £60-£80 per day.

Arkadiusz "Arek" Sniegula, trading as Armag Decoration, had no appropriate insurance and had insisted the job went ahead despite the absence of suitable equipment. Even when work on the roof resumed, he failed to ensure a safe system of work.

For fear of losing Mrs Isaacs' business he had also "sought to conceal the accident" and the judge said that suggested Mr Sniegula was "in respect of this work at least irresponsible and incompetent" and he "may have deserved the epithet of a 'cowboy' operator".

Mr Kmiecic's legal team argued that Mrs Isaacs was negligent in not allowing workmen to gain access to the garage's flat roof via a bedroom window.

But after hearing that she had white carpets, the judge said Mrs Isaacs - "a person of exacting standards" - had been entitled to object to workmen tramping through the house.

She added: "She would not have had the necessary knowledge or expertise to devise and direct Mr Kmiecic... in a safe method of carrying out the work. She was in the position in which most householders find themselves when arranging for household repairs to be carried out."