As you know, Foundation Home Loans lend on Multi-Unit Blocks, but what constitutes as a Multi-Unit Block? As part of our series on Specialist Property Buy to Let Mortgages, Gemma Lang explains: A MUB (Multi-Unit Block) is a freehold property that has been split into self-contained flats that are not subject to individual leases. This could include a block of flats or a house that has been converted into flats. Click here to read the full article.