Quality.

    Superstructure: what good looks like

    Masonry, cavity construction, wall ties, cavity trays, lintels.

    What good looks like

    Superstructure: what good looks like

    Cavity masonry, wall ties, cavity trays, lintels and the openings that decide whether the wall keeps water out.

    Superstructure is the stage that generates the most reportable items, because almost every defect is concealed by the next trade. Wall ties are the usual culprit: right type, right density, right embedment, sloping to the outer leaf and free of mortar droppings. Cavity trays and their stop ends govern where water goes when it inevitably gets into the cavity, and a tray without stop ends discharges into the inner leaf rather than out through the weep holes. Lintels need the specified end bearing on full bricks or blocks, not on a cut, and they need their own tray and weeps unless the lintel is designed to do that job. Insulation is fitted tight to the inner leaf with joints staggered and the residual cavity kept clear.

    Basis in regulation

    • Part C, clause 5.4

      External walls: resistance to moisture

      Read the source

      Checked against the live source on 20 August 2026

    Before you start

    Before you start: superstructure

    What needs to be settled before the first course goes above DPC.

    Confirm the wall tie type and length against the actual cavity width being built, not the drawing's nominal width. Have cavity tray, lintel and closer details available at the working face — most tray failures are detailing failures, not workmanship failures. Agree mortar mix and check that units, ties and trays on site match the specification. Set out openings and check head heights against the lintel schedule before the masonry commits you. Make sure scaffold lift heights let ties be built in at the right courses rather than pushed in afterwards.

    Basis in regulation

    • Part C, clause 5.3

      Cavity walls and insulation

      Read the source

      Checked against the live source on 20 August 2026

    Key requirements

    Key requirements: superstructure

    The requirements most often reported at masonry stage.

    Wall ties at the designed spacing, embedded at least 50mm into each leaf, sloping down to the outer leaf and doubled up at reveals. Cavity trays fitted with stop ends and weep holes above every opening and at every cavity interruption. Lintels bearing the specified length onto whole units at each end. Cavity kept clear of mortar droppings, with cavity boards lifted and cleaned as the work rises. Insulation held tight to the inner leaf with joints staggered and no gaps at floor junctions. Movement joints formed at the designed centres, not where they land conveniently.

    Basis in regulation

    • Part C, clause 5.4

      Cavity trays and weep holes

      Read the source

      Checked against the live source on 20 August 2026

    Wall ties and chases in separating walls

    In masonry separating cavity walls, Type A wall ties, compliant with Building Regulations, must be used. Solid separating walls can connect to the inner leaf of an external cavity wall, tied or bonded in accordance with Building Regulations or Robust Details. Chases in separating walls, which can re

    In masonry separating cavity walls, Type A wall ties, compliant with Building Regulations, must be used. Solid separating walls can connect to the inner leaf of an external cavity wall, tied or bonded in accordance with Building Regulations or Robust Details. Chases in separating walls, which can reduce sound insulation, should only be cut as specified in the design, avoiding impact tools where damage is a risk. Their depth should not exceed one-sixth of a single leaf's thickness and should not be cut in hollow blocks unless permitted by the manufacturer.

    Basis in regulation

    Proprietary punching shear systems

    In addition to traditional 'bob-and-hook' or 'U-bar' links, modern construction frequently employs proprietary systems for punching shear reinforcement in concrete slabs, particularly in multi-storey buildings. These pre-manufactured solutions, such as stud rails or shear heads, offer an efficient a

    In addition to traditional 'bob-and-hook' or 'U-bar' links, modern construction frequently employs proprietary systems for punching shear reinforcement in concrete slabs, particularly in multi-storey buildings. These pre-manufactured solutions, such as stud rails or shear heads, offer an efficient alternative to loose bars, often allowing for wider spacing while achieving the necessary structural capacity. Any such system must be fully certified and used in accordance with the manufacturer's installation guidelines and the structural engineer's design.

    Basis in regulation

    Quality Control for Masonry Construction

    All masonry must be constructed accurately, ensuring that work is level, plumb, and true to the design. This includes maintaining the specified bond pattern, using lines and spirit levels to keep courses level, ensuring perpendicular joints are aligned, and adhering to defined tolerances. Gauge rods

    All masonry must be constructed accurately, ensuring that work is level, plumb, and true to the design. This includes maintaining the specified bond pattern, using lines and spirit levels to keep courses level, ensuring perpendicular joints are aligned, and adhering to defined tolerances. Gauge rods should be used for consistent course heights and to check opening widths as work progresses. It is critical that masonry remains undisturbed and protected from vibration until the mortar has adequately set.

    Basis in regulation

    Formwork Removal and Concrete Protection

    Formwork intended for exposed concrete finishes should have tight joints to prevent grout loss and ragged edges, and its design should facilitate easy stripping without damaging the concrete. Holes for fixings must be carefully drilled to avoid surface defects. Crucially, formwork must be removed wi

    Formwork intended for exposed concrete finishes should have tight joints to prevent grout loss and ragged edges, and its design should facilitate easy stripping without damaging the concrete. Holes for fixings must be carefully drilled to avoid surface defects. Crucially, formwork must be removed without shock or disturbance to the concrete, and supports for load-bearing elements should remain in place until the concrete has achieved adequate strength as specified by the design.

    Basis in regulation

    Fireplace recess minimum dimensions

    The construction of fireplace recesses, whether in external cavity walls or internal walls, requires specific minimum dimensions for safe operation. For example, recesses built within an external cavity wall may require specific projections or clearances, while internal wall recesses have their own

    The construction of fireplace recesses, whether in external cavity walls or internal walls, requires specific minimum dimensions for safe operation. For example, recesses built within an external cavity wall may require specific projections or clearances, while internal wall recesses have their own dimensional requirements to ensure structural integrity and fire safety. These dimensions accommodate the appliance and prevent heat transfer to surrounding combustible elements.

    Basis in regulation

    Limitations for chases in separating walls

    Chases in solid separating walls have strict limitations to preserve acoustic integrity; horizontal chases must not exceed one-sixth of the leaf thickness, and vertical chases must not exceed one-third. Chases should be fully filled with mortar and staggered on opposite sides of the wall to prevent

    Chases in solid separating walls have strict limitations to preserve acoustic integrity; horizontal chases must not exceed one-sixth of the leaf thickness, and vertical chases must not exceed one-third. Chases should be fully filled with mortar and staggered on opposite sides of the wall to prevent back-to-back cutting, which would severely compromise sound insulation. Chasing is generally prohibited in hollow blocks unless explicitly permitted by the manufacturer.

    Basis in regulation

    Cavity fire barrier installation at eaves and corners

    Cavity fire barriers in external walls must be correctly installed within the cavity gap between the inner and outer leaves of masonry. At building corners or where a gable meets an external wall, the barrier should be installed vertically to maintain continuity, which may require cutting back insul

    Cavity fire barriers in external walls must be correctly installed within the cavity gap between the inner and outer leaves of masonry. At building corners or where a gable meets an external wall, the barrier should be installed vertically to maintain continuity, which may require cutting back insulation. Additionally, at party wall junctions in eaves, fire stopping should extend across the cavity and into the soffit void to compartmentalise against fire spread.

    Basis in regulation

    Reinforcement lapping for load transfer

    When individual reinforcing bars or mesh are joined, they must be lapped over a sufficient length to ensure a continuous transfer of tensile forces across the joint. The required lap length depends on the bar diameter, steel grade, concrete strength, and bond conditions, and is specified by the stru

    When individual reinforcing bars or mesh are joined, they must be lapped over a sufficient length to ensure a continuous transfer of tensile forces across the joint. The required lap length depends on the bar diameter, steel grade, concrete strength, and bond conditions, and is specified by the structural designer. Careful consideration must be given to cover depth when lapping mesh, to avoid exceeding the specified cover or requiring additional loose bars.

    Basis in regulation

    Punching shear reinforcement design

    Punching shear is a localised failure mechanism occurring in slabs subjected to concentrated loads, such as from columns. Where the concrete's shear resistance is insufficient, additional reinforcement is incorporated to transfer these forces effectively. This additional reinforcement typically cons

    Punching shear is a localised failure mechanism occurring in slabs subjected to concentrated loads, such as from columns. Where the concrete's shear resistance is insufficient, additional reinforcement is incorporated to transfer these forces effectively. This additional reinforcement typically consists of specific bar shapes, like straight bars in top/bottom layers or 'bob-and-hook' or 'U-bars' as shear links, detailed according to the structural design.

    Basis in regulation

    Concrete cover for fire resistance

    Adequate concrete cover to reinforcement is essential to ensure a structure achieves its specified fire resistance period. Eurocode 2 provides guidance on the required cover depths to protect the steel reinforcement from the effects of high temperatures during a fire event. Typically, the cover need

    Adequate concrete cover to reinforcement is essential to ensure a structure achieves its specified fire resistance period. Eurocode 2 provides guidance on the required cover depths to protect the steel reinforcement from the effects of high temperatures during a fire event. Typically, the cover needed for structural integrity under normal conditions often also provides a minimum fire resistance period for standard elements like columns, beams, and slabs.

    Basis in regulation

    Steelwork specification and durability

    Structural steelwork must meet specified strength, durability, and fire resistance requirements. The design should detail methods for fixing or connecting steel components, particularly for bolted or unconnected applications. Steel sections must conform to relevant British Standards for dimensions a

    Structural steelwork must meet specified strength, durability, and fire resistance requirements. The design should detail methods for fixing or connecting steel components, particularly for bolted or unconnected applications. Steel sections must conform to relevant British Standards for dimensions and masses. Additionally, steelwork requires an appropriate protective coating system applied prior to installation to ensure adequate durability against environmental exposure.

    Basis in regulation

    Protection against frost attack and persistent wetting

    Effective detailing is crucial to limit persistent wetting of masonry, thereby reducing the risk of frost attack and related damage. This includes ensuring external ground surfaces drain away from walls, and that sills and copings have adequately weathered surfaces and projecting throatings. Parapet

    Effective detailing is crucial to limit persistent wetting of masonry, thereby reducing the risk of frost attack and related damage. This includes ensuring external ground surfaces drain away from walls, and that sills and copings have adequately weathered surfaces and projecting throatings. Parapet and freestanding walls, unless constructed with highly durable bricks (e.g., F2/S2), must be protected by a coping with an overhang, throating, and a continuous, projecting DPC.

    Basis in regulation

    Party wall construction and blockwork junctions

    Party wall insulation should be installed progressively as the wall is built to ensure full coverage and protection from adverse weather. Where different types of masonry blocks are joined, it is standard practice to use a reinforcing mesh to maintain structural integrity across the material change.

    Party wall insulation should be installed progressively as the wall is built to ensure full coverage and protection from adverse weather. Where different types of masonry blocks are joined, it is standard practice to use a reinforcing mesh to maintain structural integrity across the material change. All excess mortar must be removed to prevent cold bridging or acoustic flaws. Working platforms must be fit for purpose and capable of safely supporting all intended loads.

    Basis in regulation

    Moisture Protection for Closed Panel Systems

    Closed panel building systems, such as timber frame or SIPs, must be robustly protected against moisture ingress to ensure long-term durability. This requires careful consideration of material choices, detailing at low levels, prevention of thermal bridging, and the effective integration of damp-pro

    Closed panel building systems, such as timber frame or SIPs, must be robustly protected against moisture ingress to ensure long-term durability. This requires careful consideration of material choices, detailing at low levels, prevention of thermal bridging, and the effective integration of damp-proof courses, membranes, and cavity trays. Proper design and installation of external wall cavities and panel junctions are crucial to prevent moisture-related issues.

    Basis in regulation

    Wall tie positioning and spacing in masonry

    Wall ties are critical for connecting masonry leaves and must be correctly spaced, both horizontally and vertically, according to design and building standards. Proper placement involves locating ties at specific intervals, including increased density around openings, and ensuring they are fully emb

    Wall ties are critical for connecting masonry leaves and must be correctly spaced, both horizontally and vertically, according to design and building standards. Proper placement involves locating ties at specific intervals, including increased density around openings, and ensuring they are fully embedded in mortar joints with correct staggering, especially with full-fill insulation. The cavity must remain clear of mortar droppings to ensure proper insulation performance and prevent bridging.

    Basis in regulation

    Critical dimensions at this stage

    Browse all critical dimensions
    England
    Low-rise traditional

    Original editorial guidance based on publicly available Approved Documents. Not building control approval, a warranty determination, or a substitute for the full source document.

    We use cookies to keep you logged in and improve ProPlot. Privacy Policy