What is a mortgage retention?

I am about to start a self build and am struggling with the costs. I am hoping to apply for a self build mortgage in order to raise the funds necessary. Could you please explain what a retention is, and when lenders might impose this as a condition of the loan?

A retention is where a mortgage lender holds back some of your mortgage funds until your home is complete. Fundamentally, this is a means for the mortgage provider to gain a bit of extra security during the course of your project. is is not normally required with the latest range of cost-based stage payment