Half Cellar floor level

[Night Owl]

Looking for a few pointers in regards to the old boiler room in my house (1950's bungalow) which would have been originally solid fuel.  It is approx. 3.28m2 and was constructed partally below ground for some reason but has long been removed. 

 

 

The floor level in the cellar is about 800mm below (slate) DPC and usually has between 6 and 12 inches of water in it during the winter months.  Picture above was taken today where it has all but finally dried out.  I want to bring the floor level up in this room to match the rest of the house, so approx. 800mm needed.  

 

My thought was to get a concrete company in to pour waterproof concrete to approx 300mm below dpc (1.64m3). Install DPM, insulation 200mm, 50mm concrete then screed to existing floor level.  Can anyone see any issues with this approach or suggest a better (easier) way?

 

Would also be interested to know why it was built below ground level.

 

Thanks.

[dpmiller]

was there a coal hatch somewhere?

[Night Owl]

Hi, no not that I can see however the door that accesses the room was on an outside wall.

[Night Owl]

Haven't found a concrete company yet interested in delivering, probably due to the small amount.  Quite a few don't carry pumping equipment too so that would be an extra hire cost.

 

Looks like it might have to be done manually   Anyone got a good formula / mix recommendation for waterproof concrete?