Beam and block floor clearance

[ashdene]

Hi, My new ground floor extension will have a beam and block floor covered with 75mm of cellotex and then a 65mm screed finish, My questions are: how much clearance will I need to allow under the beams to allow ventilation and will the area need to be covered with anything or can it just be left as clean soil?

Many Thanks

 

[jeds]

Minimum void is 150mm. Regulations don't require any form of oversite or seal but it's common to put one in of the ground isn't clean. If you do put one in it must either be above the level of surrounding ground or be drained. (either by being porous or install a drain) A common method is 50mm of no fines semi dry concrete.

 

[EB1caneyeB]

I did a block and beam floor for an 'Orangery' (oooo). Spec said as above min 150mm void 2 air bricks on each flank and oversite covered with geo-textile membrane. Ground under block and beam was left clay/soil level with ground surrounding the 'orangery'.