Our existing up and over garage door’s knackered and I want to replace it with a pair of insulated side hung doors.

The little problem I have is that the tarmac outside the doorway is slightly higher at one end which would stop one door opening outwards. To fix this I though I’d raise the existing threshold by about 60mm so the door would open over the raised tarmac.
My initial thought was to simply lay some concrete down but then I wondered whether there may be a quicker alternative.

This there something I could just buy and bed down on some suitable mastic, etc?

Pic of the existing threshold below (tiles are inside the garage) – I’d be looking to raise the concrete area which is approx 25cm x 250cm.

What’s the garage for? If not cars I’d just put a hardwood threshold down that would also make bottom edage much more weather tight.

Sorry yes it’s no longer a ‘garage’ as such as we converted half of it into a bedroom.
So now its more of a store/utility room.
Would hardwood last though?

The doors would have their own threshold which would go on top? of whatever I put down first.

A bit of pressure treated timber will last many years. A few anchor screws of gripfill or both.

As above, decent hardwood threshold or pressure treated. Concrete/mortar will just break up eventually.