Purpose
ensures uniform loading over ground
eliminates capillary void for damp
enables fill to required level
clean dry and level working surface
Includes…
brick/tile, clinker, gravel, quarry
waste, shale
Must not include…
plaster, timber, thermal block
Advantages
Good tensile strength (also compressive along grain, eg end loaded)
Short lead in time
Familiar material to workforce
Flexible in construction
Disadvantages
Limit to sizes available
Not stable
Beetle, decay and fire?
Vulnerable to poor workmanship
Too easy to adapt
Maintenance cost
Strongest woods (hardwoods) also slowest to grow
