Stephen Sheen has admitted trying to start a fire in his ex-girlfriend's flat by putting a burning sock through the window.
The 49-year-old of Pullman House, Cinderford, pleaded guilty at Gloucester Crown Court to attempted arson.
The court was told his ex-partner Gemma Jackson and her daughter were not present in the flat in High Street, Cinderford, at the time – but residents of two other flats in the building were home.
The charge Sheen admitted was that on August 21 he attempted to damage the flat belonging to Ms Jackson being reckless whether it was destroyed or damaged and also being reckless whether lives were endangered.
His denial of a more serious charge of arson with intent to endanger life was accepted by prosecutor Kirsty Real.
Ms Real said the basis of his admission was that he knew his ex-partner and daughter were not at home when he tried to set fire to it but in doing so he exposed others to danger.
Andrew Hobson, defending, asked for a pre-sentence and psychiatric report on Sheen and the judge, Recorder David Lane QC, agreed.
Sheen had been in limited contact with the mental health authorities in the past for depression and other issues, Mr Hobson said.
"Basically this case concerns him placing a burning sock into the flat," Mr Hobson said.
The ex-partner no longer lived at the same address, he added.
Recorder Lane granted Sheen bail pending sentence on February 4.
At an earlier hearing the court was told Sheen was arrested after he was seen at the foot of a ladder propped up against the High street flats at 3.45am.
He ran away when he was seen but at the side of the ladder was found a child's sock containing tissues which appeared to be singed.
The bedroom window of Ms Jackson's flat was open and a similar sock was found there. A small patch of carpet was damaged.
His fingerprint was found on one of the socks.