We are considering buying a house that has a garden plot large enough to build another house on. We are thinking about getting a self build mortgage alongside the mortgage for the property that exists already, but are wary of problems that would occur in splitting up the land between the two properties when the second is finished and how this may affect the mortgage on the existing property. Can anyone advise on how to move forward with this? Can we get a combination of mortgage/self build or would they needs to be separate mortgages?