insulation under concrete bed

1. With the insulation layer and the DPM below the concrete bed , it is necessary continue the DPM and insulation up vertically around the edges of the concrete bed to unite with the DPC in walls
2. AN advantage of positioning the DPM above the insulation is that it can be used to secure the upstand edge insulation in place while concrete is being placed
3. IF the DPM is laid below the insulation , it is necessary to spread a separating layer over the insulation to prevent wet screed running into the joints between the insulation boards
4. THe separatng layer should be building paper or 500-gauge polythene sheet
5. TO avoid damage to the insulation layer and the DPM , it is necessary to take care in tipping , spreading and compacting wet concrete or screed