Expert: Dan Griffin - 5/12/2009

Question
Dan, I have currently got two demountable homes (12m long) opposite each other with a 6m breezeway between them. The demountables are raised 1m off the ground. I wish to put a raised/suspemded slab between them as I think this may be the cheapest option. I am unsure how thick I need to go and how much bracing I will need underneath. The floor will only be used for general living area.

Answer
Dan, is this space to be outdoors or enclosed?  The least expensive way to deal with this slab would be to pour it on fill.  The actual slab would be adequate at 4" thick on well compacted fill.  YOu would need aa perimeter wall or monolithic thickened edge to keep the fill in place.  If you plan to span the slab over a void, the forms will need to be substantial and will probably be lost.  the slab will need to be about 7" with rebar, the perimeter would require walls resting on footings.

I think lumber framing and minimal bearing wall work would be less expensive.