Once you have completed the brickwork for your foundations, they need to be backfilled and waterproofed (USB) before you lay a slab to complete the foundations and start building. Here is your step-by-step guide.
Your tools:
• Spirit level
• Spade
• Square
• Compactor
• Wooden or aluminium Straight Edge
• Wheelbarrow
• Pick
Backfilling
When foundation walls are set, start backfilling with rubble and sand. Make sure the fill is compacted and does not contain vegetation. Use water to ensure compaction. Backfill to 120mm below wall level.
Laying USB
Lay a 20mm layer of sand (sifted) over backfill before laying USB.
Note: If foundation filling needs to be treated for termites, it must be done at this stage. Start laying USB over sand layer.
USB must cover the sides and go halfway over the foundation wall. Tuck USB into corners, hold into position with bricks. All overlaps must be 300mm and should be folded and sealed with jointing tape.