Although in recent times few car owners actually keep their vehicles in their garage, it has been shown that doing so does increase the chances of the vehicle suffering less deterioration to paintwork and therefore holding more of its value when being sold on. One of the reasons why people do not use their garage is that it is too small, and they are unable to get out of the vehicle easily without the risk of damaging the paintwork on the doors. How easy then is it to extend the garage to make it fit for purpose?
As long as there is sufficient land at the side of the garage to extend it out to the sides the construction should not be a problem for an experienced builder. The original garage wall can be left in situ until the new outer wall is constructed up to the roof line and then demolished later.
As most garages have a flat roof, extending the roof to meet the new wall should not be an issue and by extending the roof beams and re-felting the new roof will be watertight and strong. It is worth considering at this stage whether to put a pitched roof on instead as this will provide a useful storage area above the garage however the cost will be more than simply extending the flat roof.