The formwork block (interlock)

How this node works

Two hollow polystyrene blocks, stacked dry. Their top and bottom edges interlock like a building brick, so a course locates itself on the one below without glue or mortar. Plastic webs cast into the block hold the two EPS faces a fixed distance apart and carry the steel reinforcement in the cavity between them. Concrete poured into that continuous cavity fills it and, on hardening, becomes a monolithic reinforced wall - permanently jacketed in insulation on both faces.

Key points

• Outer form (EPS)
• Web tie of the block
• Pour cavity (R.C.)
• Interlock between courses
• Reinforcement
• Inner form (EPS)