Capital Gains on rental property I have lived in as main home

Hi, I bought a property in my name in 1998. It was my main home until 2013. I got married and bought another house with my wife (joint ownership) - the new house became my main residence and I rented out the property I bought in 1998. It has been rented out for 12 years. If I were to sell the rental property, could I claim full Private Residence Relief (PRR) on the time it was my main home? Therefore only pay capital gains on the time the property was rented out? Thank you

In addition to my above question - an old asbestos garage was removed at the property and a new detached garage was built in its place. Is the replacement garage considered an improvement?And can the cost of the garage be set against Capital Gains? Thank you.

Hi 
You can use our tool find out if you are eligilble for Private Residence Relief here:
Work out tax relief when you sell your home
Expenditure specifically for the purpose of enhancing the value of the asset is an allowable deduction in calculating the amount of the gain or loss on a disposal, normal maintenance costs, such as decorating, do not count. You can see guidance here: 
CG15150 - Expenditure: introduction
Thank you.