If you add your son's name to the title register as 'tenants in common' you'll both own half of the house. When you die your son will continue to own half of the house, with the other half being disposed of according to the terms of your will (or the intestacy rules if you've not written a will). So a 'tenancy in common' would appear not to meet your needs.
If you add your son's name to the title register as 'joint tenants' it will be your 'legal partnership' that own the house. When you die (irrespective of anything you might have written in a will) your son, as the surviving partner, would automatically acquire full ownership of the house. So a 'joint tenancy' might meet your needs.
However you need to be aware that your son (as a joint tenant) could force you to sell the house before you die, so that he could get at the money. If you'd rather that didn't happen, it would make far more sense simply to write a will leaving the house to your son.