NVQ Diploma in Bricklaying (Construction) Setting Out and Building Solid and Cavity Walls Syllabus

Define 'perpends' and state the rule for maintaining them.

Perpends are the vertical cross (head) joints between bricks. The rule is that perpends in alternate courses must align vertically (be plumb), kept directly above one another, and be of even thickness (about $10\,\text{mm}$) to give a neat, structurally correct appearance.

What is the typical specified thickness of a mortar joint (bed and perpend) in standard brickwork?

$10\,\text{mm}$ for both bed joints and perpend (cross) joints. This nominal joint, combined with the brick co-ordinating size, gives the standard gauge and bond dimensions.

What is meant by 'tolerance' in bricklaying and why is it specified?

Tolerance is the permissible amount of dimensional deviation from the specified/design dimension. It is specified because perfect accuracy is impossible on site; tolerances define acceptable limits so the work remains structurally sound, fits adjoining components and is visually acceptable.

State typical accuracy tolerances for position, verticality (plumb) and level in a brick wall (per BS guidance).

Position on plan: about $\pm10\,\text{mm}$. Verticality (plumb): about $\pm10\,\text{mm}$ in a storey height (e.g. up to $3\,\text{m}$). Level of bed joints (coursing): about $\pm10\,\text{mm}$ over a wall length, and straightness on plan about $\pm5\,\text{mm}$ in any $5\,\text{m}$ length.

What is stretcher bond and where is it normally used?

Stretcher bond is a bond in which every brick is laid as a stretcher (long face showing), with each course offset by half a brick from the one below. It is the standard bond for half-brick ($102.5\,\text{mm}$) thick walls and the leaves of cavity walls.

Explain the 'half-bond' principle and why it matters.

Half-bond means each vertical joint (perpend) is positioned at the centre of the brick in the course below, i.e. offset by half a brick length ($\approx112.5\,\text{mm}$). It ensures continuous perpends are avoided, so loads are distributed across bricks and the wall has maximum strength and stability.

What is a 'broken bond' and how is it set out?

Broken bond is used when a wall length will not divide into a whole number of brick-and-joint dimensions. The setting out is adjusted by inserting cut bricks (e.g. a three-quarter bat) to keep perpends plumb and the bond even, ideally placing the cut centrally or symmetrically rather than at a corner.

In bonding terminology, what are a stretcher, a header, a queen closer and a king closer?

Stretcher: brick laid showing its long face. Header: brick laid showing its short end face. Queen closer: a brick cut in half along its length (quarter-width) used next to the quoin header to set the bond. King closer: a brick cut diagonally to remove part of one end, used at jambs/reveals.

Describe English bond and state its main characteristic.

English bond consists of alternate courses of all headers and all stretchers. A queen closer is placed next to the quoin header to maintain the bond. It is one of the strongest brick bonds, with no continuous vertical joints through the wall thickness, often used for one-brick walls and engineering structures.

Describe Flemish bond and how it differs from English bond.

Flemish bond alternates a header and a stretcher in every single course, with each header centred over the stretcher below. Unlike English bond (whole courses of headers or stretchers), Flemish bond mixes them within each course, giving a more decorative face but slightly less strength than English bond.

Compare English bond and Flemish bond for strength and appearance.

English bond is stronger (more headers tying the wall through its thickness) and is preferred for load-bearing/structural work. Flemish bond uses fewer headers, is marginally weaker but more economical in facing bricks and is considered more decorative/attractive on the face.

What is Quetta bond and what is its purpose?

Quetta bond is a bond (based on a one-and-a-half brick thick wall) that creates a continuous internal vertical void or pocket within the wall. The pockets are filled with reinforcement and grout/concrete, producing a reinforced brick wall with improved resistance to lateral loads and seismic forces.

What is meant by 'reinforced bonding' in brickwork?

Reinforced bonding is brickwork incorporating steel reinforcement — placed in bed joints (bed-joint reinforcement) or in formed pockets/cavities (as in Quetta bond) — and grouted, to increase tensile and lateral load resistance where plain brickwork would be inadequate.

Name two examples of decorative bonding patterns used on brick faces.

Examples include: Flemish bond variants (e.g. Sussex/Single Flemish, Monk bond, Garden-wall bond), Herringbone, Basketweave, Stack bond, Dutch bond, and diaper (diamond) patterns formed with contrasting bricks. These prioritise appearance for facing/decorative panels.

What is 'stack bond' and why is it structurally weak?

Stack bond lays bricks directly on top of one another so all perpends form continuous vertical joints with no overlap (no bond). It is structurally weak because there is no load distribution between bricks; it is used only decoratively and usually requires bed-joint reinforcement.

In a cavity wall, what are the two 'leaves' and why are they built in parallel?

The two leaves are the outer leaf (usually facing brick) and the inner leaf (often blockwork). They are built in parallel (kept rising together) so that wall ties can be bedded across the cavity at the correct positions and the cavity width stays constant and clean throughout.

What is the typical width of a cavity in a UK cavity wall?

Traditionally about $50\,\text{mm}$ clear cavity; modern partial/full-fill insulated cavities are commonly $75$–$100\,\text{mm}$ or wider. The minimum residual clear cavity (with partial fill) is generally $50\,\text{mm}$.

What is the purpose of wall ties in a cavity wall?

Wall ties span the cavity to connect the two leaves, transferring lateral wind loads between them and making them act together structurally, while still allowing the cavity to resist moisture transfer. They also prevent the slender leaves from buckling independently.

State the standard spacing rule for wall ties in the field of a cavity wall.

For cavities up to $75\,\text{mm}$ with leaves $\geq90\,\text{mm}$: a maximum of $2.5$ ties per $\text{m}^{2}$, normally set out at $900\,\text{mm}$ horizontally $\times\,450\,\text{mm}$ vertically, staggered. This equals $1/(0.9\times0.45)\approx2.47$ ties per $\text{m}^{2}$.

State the wall tie spacing rule at openings, reveals and movement joints.

Additional ties must be provided at unbonded edges (jambs of openings, reveals, movement joints and roof verges). These are spaced vertically at not more than $300\,\text{mm}$ centres, within $225\,\text{mm}$ of the opening edge.

Which way should a wall tie be laid and why does the drip/twist matter?

The tie must be laid level or with a slight fall to the outer leaf, with any drip (twist or kink) pointing downwards and positioned in the middle of the cavity. This ensures water running along the tie drips off into the cavity (or to the outer leaf) rather than tracking across to the inner leaf.

Why must the cavity be kept clean and how is mortar droppings prevented?

Mortar droppings on ties or at the cavity base can bridge the cavity, allowing damp to cross to the inner leaf. The cavity is kept clean by using a cavity batten (timber/board) laid on the ties as work proceeds to catch droppings, then lifted, cleaned and reset higher.

What is a cavity batten and how is it used during construction?

A cavity batten is a length of timber (often with wires/lifting eyes) rested on a row of wall ties inside the cavity to catch mortar droppings. As the wall rises to the next tie level, the batten is lifted out, cleaned and laid back on the next ties, keeping the cavity clear.

What does DPC stand for, and what is its function in a wall?

DPC stands for Damp-Proof Course. It is an impervious horizontal (or vertical) barrier built into the wall to prevent moisture rising from the ground (rising damp) or penetrating across the structure (e.g. at openings), protecting the building from dampness.

At what minimum height above finished ground level should a horizontal DPC normally be placed?

At least $150\,\text{mm}$ ($\approx2$ brick courses) above the finished external ground/paving level, to prevent rain splash-back and ground water bridging over the top of the DPC.

What is a cavity tray (DPC tray) and where is it installed?

A cavity tray is a DPC formed across the cavity, stepping up from the outer leaf to the inner leaf, installed above openings, at abutments and where the cavity is bridged or stops. It collects water within the cavity and directs it out through weep holes to the outer face.

What are weep holes and how are they spaced above a cavity tray/lintel?

Weep holes are open perpend joints (or proprietary vents) left in the outer leaf just above a cavity tray to drain collected water to the outside. They are normally spaced at maximum $450\,\text{mm}$ centres (at least two per opening).

Explain how partial-fill versus full-fill cavity insulation is installed.

Partial-fill insulation boards are fixed against the inner leaf and held with tie clips/retaining discs, leaving a residual clear cavity ($\geq50\,\text{mm}$) on the outer side. Full-fill insulation (e.g. mineral wool batts) completely fills the cavity between the two leaves, built in as the leaves rise.

How is the cavity closed at a window or door reveal (jamb) and why?

The cavity is closed at the reveal using a vertical DPC and an insulated cavity closer, so the two leaves are sealed at the opening. This stops moisture crossing the cavity into the inner leaf and prevents a cold bridge (thermal bypass) at the jamb.

When forming an opening, what supports the masonry above and what is a key bearing rule?

A lintel (steel, concrete or other) spans the opening to carry the load of the masonry above. It must have an adequate end bearing — typically a minimum of $150\,\text{mm}$ each end onto the masonry — and be bedded level on a full mortar bed.

What is a pier in brickwork, and what is the difference between an attached pier and an isolated pier?

A pier is a thickened/strengthening column of brickwork. An attached pier is bonded into and forms part of a wall to give it extra stability or local load-bearing strength. An isolated (detached/free-standing) pier stands alone, independent of any wall, e.g. a gate pier supporting a gate or beam.

How are internal (partition) walls bonded into an external wall, and what is a junction?

A junction is where two walls meet (e.g. T-junction of an internal wall into an external wall). Bonding is achieved either by tying the internal wall into the external one with a proper masonry bond (alternate courses interlocking) or with wall ties/connectors, so loads transfer and the walls act together.

Define 'toothing' and 'indents' in brickwork.

Toothing leaves alternate bricks projecting (and recesses left) at the end of a wall so a future wall can be bonded in seamlessly. Indents are recesses (pockets) deliberately left in an existing wall into which the bricks of a new adjoining wall are built to bond the two together.

What are the main methods of forming a tie connection between a new and existing wall?

Methods include: traditional bonding/toothing (interlocking alternate courses), leaving indents to receive new brickwork, using proprietary expanding/stainless wall starter ties fixed to the existing wall with a vertical profile, and bed-joint reinforcement tied across the junction.