I'm thinking of adding a room over the garage at my place. The idea would be to build a lightweight skillion-roof room (tin roof, foamboard walls), that attaches onto the existing second storey. Have a look at the 3D drawing I've attached. This 'setback' look is a fairly common type of design that you see on two-storey project homes in new suburbs.

You can see in the drawing that while one side attaches to the existing wall, the other side has to be built halfway over the garage. You can just see the new floor and floorjoists coloured in blue, and the new steelwork coloured in green. The span of the garage door opening is 5050mm, and the span of the beam running lengthways to the back wall of the garage is 7030mm. The new room is about 5.5m long and sits about in the middle of the 7m beam.

Planning setback restrictions mean that I can't build directly over the brick garage side wall. I could make the room sit over the front and/or back garage walls, but I'd prefer not to - I'd only do that if it becomes structurally necessary.

Before I head to the structural engineer, I'm interested to know if anyone is familiar with building this type of room, because I have two questions about the beams.
1) What beams do you think are likely? I'm guessing both the garage door lintel and the main beam would be 300 x 165 steel Universal Beams.
2) The front wall of the garage is 230mm thick brickwork. Even if the brickwork above the lintel is single leaf, there is not enough room left for a 165mm UB to sit. What might be a solution?

I want to get fairly close to the likely solutions to these questions before I start burning money at the engineer's office.

KC extension.JPG KC extension - part view 2.JPG

Ta, Ian
Attached Images




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