you place scaffolding on the edge of the roof of a house until it starts falling then place a block on top of the end of the scaffolding line and continue to place more scaffolding on top of the block

What I expected to happen was...:
the scaffolding should fall of the edge of the block when placed

What actually happened was...:
you could make scaffolding lines up to hight limit

Steps to Reproduce:
1. place scaffolding on the edge of a cliff/pillar of blocks until it starts falling
2. place a block on top of the end piece of scaffolding
3. place more scaffolding on that block till it falls, then repeat step 2