Thanks so much everyone for replies. It's so helpful when trying to think things through. Just to be clearer. We have 2 properties, family home in Dublin and holiday home in the country. Both houses are currently too small. I was wondering what would happen if we moved to the country house and switched to paying interest only for a set period of 2 years on the Dublin property, which would provide us with enough money to fund an extension on the 2nd home, now our family home. After the 2 year period we would either resume full payments or sell the Dublin property depending on the market, or the bank may have already repossessed the property. I am wondering what the fallout would be if we did this without the banks permission.