I'm afraid I cannot send replies to specific email addresses but there is nothing to stop you emailing this answer to yourself.
If when you die, your estate consists of your house and little else and it is in excess of your Inheritance Tax nil rate band which is currently £325,000 and any unused part of your late spouse's nil rate band (current maximum £325,000) which your executors will be able to claim and which you can read about here
, then if there is not enough cash to pay the IHT liability, the house may need to be sold to pay it. If that was the case, then the balance of the estate would be paid to your granddaughter with no further tax to pay. If you have enough liquid assets to settle any Inheritance Tax liability, then there would be no need for your executors to sell the house.
If your granddaughter subsequently sold the house, she would have no tax to pay as it will have been her main residence for the entire period of her ownership of it.
If you gifted the house to your granddaughter and lived for seven years after making the gift, then normally it would cease to be part of your estate for IHT purposes. However, as you will continue to live there, the gift will be ineffective for IHT purposes under the reservation of benefit rules and the seven year clock would not start ticking until you renounced the reservation of benefit or paid a market rent to your granddaughter. Take a look here
for more information.
I hope this helps but let me know if you have any further questions.