Theresa May, in her party conference speech, pledged to boost council house building. This would be achieved, the prime minister said, by scrapping the existing limits on councils’ ability to borrow money.What exactly is this cap and what impact has it had? Put simply, it applies to something called a Housing Revenue Account (HRA) – the pot of money where councils in England manage their housing revenue and expenditure. But since 2012, the rules around HRAs have been tightened to restrict the amount that local authorities can draw down to build new social housing. Forty years ago, local authorities were responsible for more than 40% of house builds. Last year, it was less than 2%, according to government statistics. However, the construction of homes by local councils had been falling for several decades before the borrowing cap was imposed.