Masonry Notes and Specifications

Structural steelwork transfers loads back into the surrounding masonry through padstones, base plates, and frame cramps. The masonry must be capable of receiving and distributing those loads. Poor or deteriorated masonry will crush under localised bearing pressure — even where a padstone is correctly sized for the wall area — if the mortar joints are open or the units are cracked.

Condition of Existing Masonry

Before any steelwork is installed, inspect the masonry at all bearing locations. If mortar joints are open, crumbling, or absent, or if masonry units are cracked or spalled, the masonry must be re-pointed or replaced before loading commences.

Do not install padstones onto poor-quality brickwork or blockwork on the assumption that the padstone will compensate. A padstone spreads the load over a larger area — but if the masonry below cannot carry even distributed load at that area, the padstone will punch through.

Block Orientation: Narrow Edge Up

Where concrete blocks are used as padstones or load-bearing courses under steelwork, they must be oriented with the narrow edge uppermost (i.e. on edge, not flat). This orientation places the block in its strongest configuration — the full height of the block carries the compressive load, rather than the less stiff flat dimension.

Do not lay blocks flat unless specifically detailed and approved.

Restraint Strapping

All floors and roofs connected to or adjacent to steelwork must be restrained against horizontal movement in accordance with Diagrams 15 and 16 of Approved Document A (Part A of the Building Regulations — Structure).

These restraint straps prevent the wall from moving out of plane relative to the floor or roof — a critical requirement at beam ends and at gable walls.

Restraint straps must be:
– At maximum 2 m centres unless the Diagram indicates otherwise
– Installed at time of construction — not retrofitted after the structure is loaded
– Correctly embedded into the masonry (folded over the face or built into the bed joint)

Movement Joints

Masonry expands and contracts with temperature and moisture changes. Without movement joints, long masonry runs develop cracks at their weakest points (typically at corners or near openings). The specification requires:

– Movement joints at maximum 6 m centres in blockwork
– Movement joints at maximum 12 m centres in brickwork

Where Movement Joints Are Not Achievable

In some layouts — particularly around openings in constrained plans — achieving these spacings is not possible. Where the required joint spacing cannot be achieved architecturally, the specification requires bed joint reinforcement installed horizontally at 450 mm vertical centres in the masonry. This reinforcement provides lateral continuity across cracks that do form, reducing their width and preventing progressive cracking.

Bed joint reinforcement (typically galvanised steel ladder mesh or expanded metal strip) must be compatible with the mortar type and must extend from the centre of one restraint point to the next.

Contact us if you have questions about masonry specification for your project.