Can footings be easily strengthened?

Hi
We are in the middle of planning - and want to add a room to the front of our double brick and tile house. The new 5m long room will join (like two squares together) along side our single brick wall garage (tiled roof), which has a pillar at the front, one pillar in the middle and the back corner joins to our
house. Single brick infill between pillars. The strip footing under the garage wall is 200x200 according to the 7yr old plan.

My draftsman thinks that we should demolish the complete side garage wall and pillars, dig out the footing and redo a 250h x 450W footing to build the new double brick wall on top. Gasp I thought, that looks like a lot of work and energy for no apparent gain, not to mention the headache of clearing out the garage and storing it elsewhere for security reasons.

I want to keep the 200x200 footing and pour an additional footing along side (joined with 12mm dowels), and then the new slab for the extension on top. To lighten the load a bit, I'll probably go with a steel framed stud inner wall for new room.

What do others think of this?
Is is normal practise, and can it still be structurally sound to just pour a new footing along side an existing one to support a double brick wall where there was previously a single one?
If you have done this or know of a builder/engineer in PERTH who can advise, please let me know.

Cheers
C


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