Extending your mortgage is a popular way of funding large home improvements that are intended to increase the value of your property, therefore justifying the fact that you will be paying it off over a longer period.
This is often referred to as ‘secured lending,' because the money is borrowed against your home. If you cannot pay, the lender has a greater chance of getting their money back because ultimately, they can go to court and claim your house in lieu of your repayments.
The main benefit of funding your home improvement with a bigger mortgage is that you can spread the payment over the remaining term of your loan. So, if you have 20 years left to pay off your mortgage, you have 20 years to pay off the cost of extra borrowing, and so the increase in your monthly outgoings will be smaller than with other methods of borrowing.