EXTENDING BASE HELP PLEASE All manner of questions and solutions to problems and issues surrounding the subject of brickwork, blockwork and stonework

[tooladdict]

After looking at the amount of advice people have got on their various projects I thought Id take the plunge!...

We are extending the existing garden room and replacing the existing structure with (a non leaking) green oak version with the cill place sitting directly on the base.

The existing garden room is built on a base 800mm above ground level, I always presumed this would be solid concrete but after further web investigation I doubt it.

The added extension of this would be 3m x 2.5 x 800mm deep not including the foundations and belown ground level blockwork and my questions are...

1. Do I need to tie the extended base into the existing base and the existing house structure and if so how?

2. Do I need to build a cavity wall up to floor height or should it be solid wall?

3. If cavity how do I cose the the top and how does this work with DPC etc?

4. Do I need to use a suspended timber floor due to the height from ground level?

Thanks for all your time..

[stoneyboy]

tooladdict,
I would not recommend a solid floor, with a height of 0.8m above ground level I doubt whether a cavity wall would withstand the sideways pressure.
The easiest solution would probably be to use concrete beams with a floor screed (and insulation if you want it) leaving a cavity below.
Assuming the new will be larger than the old and outside it the existing floor and walls can be used for infill. If the existing walls are to be utilised you will need to tooth or corbel them back and build the new walls from there. The top of the cavity wall can be closed with bricks with a vertical dpc.
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