Padstone

A padstone is a solid block of dense, high strength concrete built into a wall under the end of a beam or lintel. It's usually precast to a size that courses in with the brickwork or blockwork around it, such as 440 x 140 x 102 or 440 x 215 x 100.

The end of a beam delivers a lot of load onto a small area. Ordinary bricks or lightweight blocks can crush under that concentrated load, so the padstone sits between the beam and the wall and spreads the load out over a longer length of masonry, at a pressure the wall can take.

It also gives the beam a level, solid seat to sit on.

Under each end of steel beams and heavily loaded lintels: knock-throughs, wide openings, and beams carrying floors or other beams. They're most important where the wall below is lightweight blockwork.

• Precast concrete padstones: the usual choice, in stock sizes that course with brick and block (lengths of 215, 330, 440 and 660 are common). Typically C40/50 concrete or stronger.
• Cast in place padstones: concrete poured into a formed pocket, for odd sizes.
• Engineering bricks: a few courses of Class A or B engineering brick sometimes stand in for a padstone, where the engineer allows it.

The size is set by the structural engineer from the load at the beam's end and the strength of the masonry below. The padstone is bedded on a full bed of mortar, set level, and all padstones under one beam are set to the same height so the beam sits level.

• The pocket it goes into must be cut back to solid, sound masonry and cleaned out. Flues, voids or soft bricks under it need the engineer's advice.
• The bedding mortar should go off before the beam's weight goes onto it.

• Steel Beam: sits on the padstone at each end
• Brick / Blockwork: the padstone is built into the leaf and spreads the load into it