Brickwork walls construction

[daveob]

Need advise please, before a builder pulls the wool over my eyes.

I have a double garage ( with a centre wall separating them ) and am seriously considering building upwards ( sideways is not an option because of land slope and layout, and the sea view from the top floor would be stunning ). I want to add a double room flat above the garage, with a concrete slab between, and a tiled roof.

I was told that the existing single thickness wall must be increased to a double thickness wall, which I understand would be needed to take the weight of the slab and top floor walling ( in addition to the existing tiled roof's weight ).

So what's the procedure ?

Would the existing concrete floor need to be lifted to increase the foundation width ?
How is the new (inside) wall attached to the existing wall ? I assume the two need to be fixed together somehow.

Would the walls on the top floor all be single thickness ? My thinking is that if the existing single layer brick walls can support the existing tiled roof, the same should apply on the top floor, as long as the ground floor walls can support the slab and top floor walls.

Not too sure what technical terms to google, so any experienced advise would be appreciated.

[Just Gone]

Firstly u need to check that the foundations are the correct foundations for a double story. All outside walls should be double walls bottom and top! unless your building was an informal building! Dont understand why they arent.

[AndyD]

They do have a tendancy to build garages using single skin walls because cold and a little damp aren't so much of an issue but the builder's right, double skin walls would be necessary to make it a double storey, especially for a dwelling. The wall skins are usually tied together using wire butterflies and brickforce is also used every few courses of bricks to add strength.

The foundations will probable need upgrading but you might be best to expose the foundations in 2 or 3 places and get a structural engineer to suggest a spec, it will be a couple of grand well spent. I doubt you'll need to mess with the existing floor level but the what upgrading would be required depends much on the soil type, ground water/drainage, existing foundation sizes, type of build structure, ground slope etc etc.

[wynn]

Another option is to install columns or stilts of either concrete or steel, mounted on new concrete pads, around the outside and support the new concrete floor that way, I would recommend a concrete plank and block floor for the least fuss.
Build the top structure with (SIPS) nu-tech panels (like a drywall structure but good for external use) to keep the weight down, looks pretty and is extremely functional.

there is a product called 'Windeck' which consists of prestressed concrete beams with a concrete tile resting between (simmilar to plank and block) also very pretty but I don't think you will be able to use it as a fire barrier?