Krogers

150mm type 1 50mm sand radon membrane a252 mesh 150mm c35 followed by 120mm insulation 80mm of screed is my floor make up My issue was forming the cavity @ GL hence the original query of forming the cavity within the trench block As I have built the trench block to high and didn’t want to cut them or knock them down!!! so the original gl for the slab was 60.00 I’ve added an additional 60.225 as I asked them to so new GL 60.225 I should of formed the cavity @ 59.775 hence asking if I could form the cavity so now I have to form the cavity @ 60.225 ( above the trench block) which by the time I add screed and insulation takes me to 60.500 FFL ?? Which is fine I either have to take down the trench block and form the cavity or put a 4’ block around and lap the dpc over. But I wondered if I could lap up over the trench and start the cavity on the trench hopefully that makes some sence pictures may be easier tomorrow when I’m back to figure this out

Hi Peter, no height limitation, outer wall is render I was hoping to use the concrete trench within the slab then form the cavity on top of the slab but what your saying is I should put a 4’ block around and use that to cast my slab into??

What are we classing as DPC as there is another dpc above which has got me confused --------------------FFL top of screed ] [--- if i bring my visqueen up and over? -------------------GL @ top of trench currently If i can form my cavity on top of the trench there will be another 225mm of block work above? Have i over complicated all this Keith.

PIcture of trench block

Please see rough sketch attached its a ground bearing slab not block & beam

I have been browsing for a while and finally made an account So I have started my timber frame self build pictures to follow. The foundations are poured, and I'm project managing the brickies as best as I can but think I may have made an error and wanted to check on here before I embarrass my self and potentially have to take down their work or cut it back with a disc cutter 300mm concrete trench blocks have been laid so far but I decided to alter the floor level slightly. I told them to build 900mm of trench block which would off took me to ground level, I then decided to get them to add another 225mm of trench block as I felt the plot sat to low but this is where I think I may have gone wrong I should of got them to form the cavity @ 675mm then continue with 4inch block to take me to 900mm and not continue in trench??? As now to form a cavity ill be increasing the plot by another 225mm?? Or can I cast my 150mm concrete slab into the trench block they’ve already built and bring my dpm over the trench block and then form a cavity off that trench block going up? Ive got 150mm reinforced concrete slab followed by 120mm insulation & 80mm of screed so there will be another dpm/dpc to follow after the trench?? I know they say getting out the ground is the hardest!!! I see why now Keith