Help with pouring basement concrete floors Ask questions and find answers on a range of subjects relating to self build projects

[TOKENKING]

Hi,
I have a few questions about concrete floors that I’m trying to get answers to before I contact BC.
This is a DIY basement refurb with building control approval. DPM has been inspected and OK to pour concrete floors. There are four separate rooms to pour ranging from 13.7 Msq to 3.8 Msq all at 100mm thick. Jabcore hardcore replacement/insulation 100mm thick is installed above DPM with an additional layer of DPM covering ready for concrete. My plans require “100mm of concrete” with no further detail. Site access is terrible and I want to avoid ready mixed and pumping in as it will need to be done in two phases due to room layout. My preference is to do It with a couple of mixers and lots of hard work doing a room at a time.

Is it a requirement to reinforce the concrete as it has an insulation layer below? If so what type?

I’ve looked at NHBC standards for site mixed concrete to try and get a guide on what mix to use
ST 2 or ST3 if un reinforced, ST5 if Reinforced.
What proportions would a builder use If I got them to do it and would they reinforce it?
Any comments/ help/advice is most welcome
Cheers

[stoneyboy]

Hi tokenking
You should aim for st3 or st4, whether you use reinforcement will depend on loads on the floor. If you go manual mixing you will need 75+ mixes in a 1 bag mixer. The electric mixers are usually 1/2 bag so 150 mixes.
Gauging of the mixes is important and this is where consistency can go wrong.
Don’t forget edge insulation which will also allow for expansion.
Regards S

[TOKENKING]

Hi Stoneyboy,
Thanks for the reply. I think I'm going for ST4. The ground conditions below the floor are well compacted building rubble and soil that I used a whacker plate on prior to compacting the sand blinding. I don't think it needs any reinforcing for loadings as its just a domestic floor but I might use A252 mesh centrally placed to prevent shrinkage cracking. I have a half bag mixer so I'm going to start with the smallest room and see how it turns out.
Is the edge insulation OK at 50mm thick? BC are happy with U values for the floor as is and all external walls will have 100ml insulation in the stud walls.
Thanks again for your help with this.
Cheers

[stoneyboy]

Hi tokenking
50mm will be fine.
Regards S