NVQ Diploma in Bricklaying (Construction) Repair, Maintenance and Cladding Systems Syllabus

Repair, Maintenance and Cladding Systems syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Repair, Maintenance and Cladding Systems in NVQ Diploma in Bricklaying (Construction), not a summary of it.

1. 1

   Diagnosing Defects in Masonry

   4 topics

   • Cracking, settlement and subsidence indicators
   • Damp problems: rising, penetrating and condensation
     • Efflorescence and salt attack
   • Spalling, sulphate attack and frost damage
   • Wall tie failure and cavity defects
2. 2

   Repair and Replacement Techniques

   5 topics

   • Cutting out and replacing damaged units
   • Repointing techniques and lime mortar repair
     • Matching historic mortars and conservation work
   • Installing remedial wall ties and crack stitching
   • Inserting retro-fit damp-proof courses
   • Underpinning principles and temporary support
3. 3

   Thin-Joint and Modern Masonry Systems

   3 topics

   • Thin-joint blockwork and adhesive mortars
   • Aircrete systems and rapid build methods
   • Movement joints in modern masonry
4. 4

   Cladding and Rainscreen Brickwork

   3 topics

   • Brick slip and mechanically fixed cladding systems
   • Support angles, brackets and restraint fixings
   • Sealants, mastics and weatherproofing details

Repair, Maintenance and Cladding Systems flashcards for NVQ Diploma in Bricklaying (Construction)

18 of 49 cards from the Repair, Maintenance and Cladding Systems deck — real questions with worked answers.

1. What are the three classic structural movement indicators a surveyor looks for, and how do they differ in cause?

   Cracking (stress relief from differential movement), settlement (downward movement of the building under its own load as the ground consolidates, usually uniform/early), and subsidence (downward ground movement unrelated to the building's load, e.g. clay shrinkage, leaking drains, mining). Settlement is the building bedding in; subsidence is the ground failing beneath it.

2. How can crack orientation help diagnose subsidence versus thermal/seasonal movement?

   Subsidence cracks are typically diagonal, wider at the top than the bottom (or wider at one end), often follow the weak mortar line in a stepped pattern through brickwork, and pass through both the wall and any rendering. Thermal/seasonal cracks tend to be fine, uniform-width, and open and close with the seasons.

3. On the BRE crack-width classification, what category and width range is considered the threshold where cracking becomes structurally significant rather than merely aesthetic?

   Category 2 covers cracks up to about $5\,\text{mm}$ (slight, filled on redecoration). Significance increases at Category 3 ($5$ to $15\,\text{mm}$, may need some masonry replacement). Cracks below $1\,\text{mm}$ (Category 0/1) are negligible to very slight and aesthetic only.

4. What is the leading cause of clay-soil subsidence in the UK and a common aggravating factor?

   Seasonal shrinkage and swelling of shrinkable clay soils due to changing moisture content. The most common aggravating factor is the desiccating effect of nearby tree roots drawing moisture from the clay (and conversely, heave when trees are removed).

5. Define rising damp and state how it is driven and its typical height limit.

   Rising damp is ground moisture drawn upward through porous masonry by capillary action where there is no effective damp-proof course. It typically rises to about $1\,\text{m}$ above ground level, limited by the balance between capillarity and evaporation, and leaves a tide mark with hygroscopic salts (nitrates/chlorides).

6. Distinguish penetrating damp from rising damp in cause and pattern.

   Penetrating damp enters laterally through the wall fabric from outside (defective pointing, cracked render, failed flashings, blocked cavity, spalled bricks). It appears as localised, often higher-level patches that worsen after rain, whereas rising damp is confined to the base of the wall and is fairly constant.

7. What causes condensation dampness and what is the key parameter governing it?

   Condensation occurs when warm, moist internal air contacts a surface at or below its dew point, so water vapour condenses to liquid. The key parameter is surface temperature relative to the dew-point temperature; cold bridges and poor ventilation/insulation promote it, typically showing as black mould in corners and on cold surfaces.

8. How can salt analysis distinguish rising damp from condensation?

   Rising damp brings up groundwater salts, so a salts band (nitrates and chlorides) is found at the top of the rise. Condensation is distilled water with no salt deposition. Presence of hygroscopic nitrate/chloride salts therefore indicates rising rather than condensation dampness.

9. What is spalling of brickwork and what is the underlying mechanism?

   Spalling is the flaking, crumbling or breaking away of the face of a brick or masonry unit. The usual mechanism is freeze-thaw: water absorbed into a saturated, non-frost-resistant brick freezes and expands by about $9\%$, generating internal pressure that fractures the face.

10. Explain sulphate attack on mortar: the reaction, the visible signs, and a key prerequisite.

    Soluble sulphates (from bricks, soil or groundwater) react with the tricalcium aluminate ($\ce{C3A}$) in Portland cement to form expansive ettringite, which swells the mortar. Signs are horizontal cracking along bed joints, expansion/bulging and render oversailing. A key prerequisite is persistent saturation (water), so it is common in chimneys, parapets and retaining walls.

11. What brick frost-resistance and soluble-salt designations are used to specify durable masonry?

    Frost resistance: F2 (freeze/thaw resistant, formerly F), F1 (moderately), F0 (not frost resistant). Soluble salt content: S2 (low, formerly L) and S1 (normal, formerly N). For exposed work such as parapets and below DPC, specify F2,S2 bricks.

12. Why are parapets, copings and freestanding walls especially prone to frost and sulphate damage?

    They are exposed to wetting on two or more faces and cannot dry from a sheltered side, so they remain saturated for long periods. High moisture content drives both freeze-thaw spalling and sulphate attack, which is why frost-resistant, low-sulphate units (F2,S2) and effective copings/DPCs are essential.

13. List the main causes and consequences of wall tie failure in older cavity walls.

    Causes: corrosion of unprotected/galvanised steel ties (the zinc coating depletes), embedment in aggressive mortar, or poor original installation. Consequences: the leaf becomes structurally disconnected, leading to horizontal cracking at regular tie-course intervals, bulging or bowing of the outer leaf, and risk of collapse. Corroding ties also expand and can lift bed joints (about every sixth course).

14. What regular crack pattern is the diagnostic signature of wall tie corrosion?

    Horizontal cracking in the bed joints at regular vertical intervals corresponding to the tie spacing — typically every $450\,\text{mm}$ (about every sixth course) — caused by the expanding rust (which occupies several times the volume of the original steel) jacking the joints open. The outer leaf may also bow outward.

15. State the typical maximum spacing requirements for wall ties in a standard cavity wall.

    Generally $900\,\text{mm}$ horizontally and $450\,\text{mm}$ vertically, giving roughly $2.5$ ties per $\text{m}^{2}$. At openings, movement joints and free edges (within $225\,\text{mm}$), ties are placed at maximum $300\,\text{mm}$ vertical centres.

16. Describe the correct procedure for cutting out and replacing a damaged brick.

    Rake/drill out the surrounding mortar joints, carefully cut and remove the spalled brick (without damaging neighbours), clean and dampen the opening, butter the bed and perpends of a matching replacement brick, push it firmly into place to align with the face, then point up the joints to match the existing profile and colour.

17. What is a 'bat' replacement and when is it used in masonry repair?

    A bat is a cut portion of a brick. When a face is spalled but the brick cannot be fully removed (e.g. a header tying into the structure), a brick slip or bat of matching brick is bonded into the cut-back face to restore appearance and weathering without disturbing the full unit.

18. What is repointing, and why is over-raking or grinding joints discouraged on heritage brickwork?

    Repointing is raking out decayed mortar to a sound depth (typically $2$ to $2.5$ times the joint width, about $15$ to $20\,\text{mm}$) and replacing it with fresh mortar. Disc-grinders are discouraged because they widen joints, damage arrises and the soft historic bricks, harming both appearance and weathering.

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