Replacing wooden floor with concrete

[subzero]

Hi

We have taken up a wooden ground floor (joists and fibreboard) due to problems with joists rotting caused by inadequate airflow.

We want to install a concrete floor as a replacement.

Having done a bit of research about how to go about this, would like to know if we are proceeding correctly -

There is approx a 2ft depth down to a base soil layer

We have begun by laying a 'hardcore' base of old bricks and rubble, to bring the base level up a bit.

What should be next? -

Layer of sand
DPM
2nd layer of sand
Concrete (what sort - fibre mix?)
Screed (is screed really necessary?)

OR

Millwaste
Sand
DPM
Sand
Concrete

?

Also does the perimeter of the concrete floor require a polystyrene buffer between the concrete and the brick walls?

The layer of bricks at floor level has been damp-proof injected at some point (10 years+). Will this require another treatment or does it not matter if concreting?

Many thanks in advance

 

[RedHerring2]

You ought to install some insulation.

100mm minimum hardcore
50 mm sand blinding
dpm
100mm insulation
waterproof membrane (to stop the water from the concrete being lost throught he insulation. You could tape the joins instaed, but the barrier is better)
100mm concrete
30mm+ screed.

Ensure that the dpm laps up and past the dpc in the walls.
25mm upstand of insulation around the edge. I always place this before placing the 100mm bottom ones. It helps to keep the side ones in place.

I can't comment on the dpc injected into the walls, It depends on the efficacy of it.

Are you confident that you won't be reducing the ventilation to other underfloor areas?