Padstone
/ ˈpadstəʊn /
Also known as: bearing pad, template, spreader
Definition
A padstone is a block of dense concrete, engineering brick, or natural stone placed under the end of a beam, RSJ, or lintel where it bears on a masonry wall. Its purpose is to spread the concentrated point load from the beam over a larger area of brickwork or blockwork, preventing localised crushing of the masonry beneath. Without a padstone, the high stress at the bearing point can crack or collapse the wall below.
In practice
Padstone size is specified by the structural engineer as part of the beam design, and depends on the load to be transferred and the compressive strength of the supporting masonry. A minimum size for a lightly loaded domestic RSJ might be one brick course (215x102x65mm), while heavily loaded beams may require padstones several courses deep or cast as a reinforced concrete pad.
The padstone must be bedded level on fresh mortar and positioned centrally under the beam bearing point. Omitting a padstone, or using a standard brick instead of a dense engineering brick or concrete block, is one of the most common and dangerous installation errors - it can cause progressive crushing and cracking of the wall below the beam end.
Building Regulations
Padstone specification forms part of the structural engineer's calculations submitted with any beam installation application to Building Control. The size, material, and compressive strength of the padstone must be sufficient to distribute the reaction load safely into the supporting masonry without exceeding its allowable bearing stress.
Full Building Regulations guidanceSee also