Re-roofing a1930's house

[tukky142]

Hi,

I am about to have an extension built to my house. The extension will add a gable end to the one side of the house.
The roof tiles are original and dont have felt under them. My question is if I get the whole roof done can the tiles be re-used and felt is added under neath or do they normally replace all the timbers and use new tiles?
I am trying to gauge if its good practice to replace the tiles or is the re-use of tiles a normal practise.

Thanks in advance

 

[Static]

Re-laying the old tiles is common practice unless the tiles have degraded too much. Also blends in with surrounding houses.