Saffron for Intermediaries has launched a lower-rate mortgage for self-builders as part of an "autumn sale".
The lender has offered self-builders a variable mortgage rate reduced from 4.45 per cent to 4.20 per cent for a limited time.
The mortgage is available to first time buyers and clients can have up to five times their income considered on application.
Self-build is growing in popularity with Ipsos Mori showing that one in seven people in the UK look into building their own homes.
Colin Field, chief executive of Saffron Building Society, said: "We know there is growing demand for self-build homes and we want to support our brokers and their customers who are keen to go it alone on a building project.
"Many will have taken time off during the summer giving them head space to plan their dream ‘self-build’ house project. Our Autumn Sale will now help in that next step, getting the finances in place to make this dream become a reality."
He added: "A project like this may seem daunting to many but one of our specialist team will be pleased to help customers complete this important step in the process – helping to reduce the stress."
Every application is manually assessed by a specialist self-build underwriter and offers flexible stage payments, so funds can be tailored to each individual projects.
Robert Sinclair, chief executive of the Association of Mortgage Intermediaries, said: "In a world where self-build is becoming more popular it is great to see the mutual sector immersing itself with great offers to the public and via the broker community.
"Ultimately any affordability assessment should revolve around affordability rather than income multiples, but of course some societies may wish to limit their exposure by applying this constraint as well."
The term is for 24 months and clients must re-finance at the end of the product term.