cost to raise the ground level - flood prone area

Hi All,

i'm looking at a site where its in flood prone area in victoria and i believe they will ask to lift the floor level by 350mm. does anyone know how much it costs per m2 to to fill in the land? or would it be better to build on stumps?

also the below photo would that just be on stumps?

 

350mm might not be enough to protect given increased rainfall due to climate ..... storm surge as well.

I would think the engineering might e 25k, but the risk of flooding will still exist.

 

The requirement if for habitable area floor levels to be 300mm above the designated flood level. You will need to know what the flood level will be then add 300mm. Once you know that you can decide on floor structure

 

I would say that’s probably not on stumps but is a slab that has a turned down edge.

 

The way to tell if a brick house in on stumps, is to look for the ventilation grilles.

A brick house on stumps, in Victoria, should have regularly spaced ventilation grilles set into the brickwork below floor level (i.e. to ventilate the subfloor). They will be visible from the outside.

 

Whether council will approve a slab is another matter - some will require bearers & joists so as not to affect overland flow.

 

cheers for that, do you know how much additional cost it would be per m2 / TH to do different foundation/raise the ffl? as apparently slab is cheapest for flat blocks.

 

Sorry, I don't know the answer to that. It would depend on the height and other structural issues. Turned down edges are good for up to around 400mm to get a flat slab but they are generally used for blocks that have a slight slope to get a flat slab. An engineer and council/state policy would need to be consulted to see what type of slab would be approved for that particular flood zone requirements.

 

i looked at the sewer interactive online maps and was able to get RL levels from neighbouring properties the photo above had 100mm below flood level so that kinda makes sense as it looks to be about 400mm above ground from the screenshot above unfortunately the block i'm looking at is about 345mm below flood level requiring it to be 645mm minimum above flood level. at that heigh range for a flat block what would you think would be most suitable construction for foundation? block can do 4 townhouses potentially 5. i find this interesting the building side of it.

 

In my experience the regulations wouldn't allow density like that on a block with some floodzone. This is not gospel but density and floods don't mix as it impedes the flow of water too much. In WA you wouldn't be able to do it at all but I gather in other states they are more relaxed.
645mm is a much larger height - you'd really need some specific advice before purchasing as it adds a lot to the complexity and possible cost.

 

all around it is town house sites, neighbouring property is 4 villas most recent one was the above screenshot one which was a adjoining lot for 5 townhouses built in 2015 another adjoining one is 3-4 th