Nationwide has doubled its maximum personal loan amount from £25,000 to £50,000.
The building society said its decision would help customers cope with rising construction costs, with many turning to loans to help with home improvement projects.
More than four in 10 households were hoping to start renovation plans and the end of this month, it said.
But, with recent forecasts predicting a 15% uplift in building costs over the next five years, they could be facing much steeper bills.
"With the impact of inflation and other external pressures, the costs of construction have seen significant increases in recent years," said head of personal loans at Nationwide Darren Bailey.
"However, we recognise many people will want to continue with the home improvement plans, even if that means they have downscaled their plans to accommodate their budget.
"Our increased maximum personal loan size of £50,000 means we have an option to suit everyone."
The increased loan amount will be available to Nationwide current account holders.
Customers can apply for the loan online, in branch or on the phone and receive the money the same day.