Quality Control for Masonry Works: Blockwork, Brickwork and Plaster

Masonry works are the backbone of many structures, providing strength and enclosure. Whether you are building a low rise residence or a commercial tower, the quality of blockwork, brickwork and plaster determines durability and appearance. This article looks at how to control quality throughout the masonry process, from selecting units to applying the final coat of plaster.

Who this helps:

- Junior quantity surveyors learning how to measure masonry works in BOQs

- Estimators preparing cost plans for brick and block walls

- Site engineers managing daily masonry activities

- Quality control managers ensuring compliance with codes in India and GCC

Foundations of masonry works:

Masonry involves assembling individual units with mortar to form walls, columns and partitions. Bricks are fired clay units with high compressive strength, while concrete blocks and AAC blocks are lighter alternatives used for external and partition walls. Mortar binds the units and is made from cement, sand and water. Plaster is a thin layer of mortar or gypsum applied to achieve a smooth finish. Proper selection and storage of materials is crucial – bricks should be uniform and free from cracks, blocks should meet density requirements, sand should be clean, and cement should be fresh.

Step-by-step quality control process:

1. Material approval – Inspect bricks or blocks for dimensions, strength certificates and visual defects. Ensure sand is washed and graded, cement bags are stored in a dry area, and water is potable.

2. Mortar preparation – Calculate the ratio based on project specifications. Common mixes are 1:4 for brickwork and 1:6 for blockwork. Measure cement and sand by volume using gauge boxes. Mix dry materials thoroughly before adding water gradually.

3. Laying bricks or blocks – Set out walls using a reference line. Wet clay bricks slightly before laying but do not soak concrete blocks. Spread a mortar bed of uniform thickness, typically 10 millimetres. Place each unit gently and tap into position, checking alignment and level with a spirit level. Stagger joints in successive courses.

4. Vertical and horizontal alignment – Use plumb bobs and lines to maintain straight vertical walls. Check horizontal levels every course. Maintain consistent joint thickness for aesthetics and structural performance.

5. Reinforcement and ties – Install steel bars or wire mesh at specified intervals in masonry walls subject to lateral loads. Provide wall ties at junctions and openings.

6. Curing – Keep masonry moist for at least seven days to ensure proper hydration of the cement. This prevents shrinkage cracks and improves strength. Cover walls with hessian cloth and sprinkle water regularly.

7. Plaster application – Before plastering, hack or roughen the surface for mechanical key. Apply a dash coat to improve bond. Mix plaster in the specified ratio, usually 1:4 or 1:5 cement to sand. Apply in two coats: a base coat of 12 millimetres and a finishing coat of 3 millimetres. Use a straight edge to achieve even thickness and check plumb.

8. Inspection and documentation – Record test results and inspection reports. Address any non-conformance immediately.

Example quality control parameters:

| Parameter | Test or inspection | Acceptable value |

| Compressive strength of bricks | Laboratory test on sample units | ≥ 3.5 MPa for common bricks |

| Density of concrete blocks | Manufacturer certificate and random sample checks | 1,800 to 2,400 kg per cubic metre |

| Mortar mix ratio | Volume ratio of cement to sand | 1:4 to 1:6 depending on specification |

| Joint thickness | Measurement with gauge rod | 10 to 12 mm uniform |

| Plaster thickness | Measurement with depth gauge | 12 to 15 mm total |

Useful formulas:

- Masonry volume = wall length × wall thickness × wall height

- Number of bricks = masonry volume ÷ volume of one brick (standard brick volume is 0.00198 cubic metres)

- Mortar volume = masonry volume × mortar factor (typically 0.25 for brickwork)

India versus GCC considerations:

In India, burnt clay bricks are widely used for load bearing walls and partitions. Mortar mixes of 1:4 for brickwork and 1:6 for plaster are common. Plaster is generally applied in two coats with a total thickness of about 15 millimetres. In Gulf countries, concrete blocks and AAC blocks are preferred due to fire resistance and thermal insulation. Mortar mixes may be leaner, such as 1:6, and plasters may include gypsum finishes. Standards such as IS 1905 in India and ASTM C90 or BS EN 771 in GCC regions govern masonry units. Climatic conditions also influence curing practices – hot, dry climates in the GCC require more frequent curing to avoid rapid drying.

Common mistakes and how to fix them:

- Using overburnt or underburnt bricks leads to weak masonry; reject defective units and source from approved suppliers.

- Inconsistent mortar proportions cause weak joints; ensure proper measurement and mixing.

- Excessive joint thickness creates weak points; train masons to maintain uniform joints.

- Insufficient curing results in cracks and reduced strength; implement a curing schedule and assign responsibility.

- Plaster applied on dusty or oily surfaces leads to debonding; clean and dampen surfaces before plastering.

- Applying thick plaster in one coat causes shrinkage cracks; always apply in two thin coats.

Mini quality control checklist:

- Verify supplier certificates for bricks, blocks and cement.

- Check moisture content of bricks before laying.

- Ensure correct mortar ratio using gauge boxes.

- Use guiding lines to control alignment and level.

- Maintain uniform joint thickness across courses.

- Insert reinforcement and wall ties as specified.

- Inspect blocks for hollow cells filled with grout where required.

- Keep masonry moist for seven days to aid curing.

- Scratch plaster surfaces for better adhesion between coats.

- Document all inspections and corrective actions.

Frequently asked questions:

Question: Why is curing so important for masonry works?

Answer: Curing allows cement in the mortar and plaster to hydrate properly, which increases strength and prevents shrinkage cracks. Without adequate moisture, masonry becomes brittle and prone to failure.

Question: How do block walls differ from brick walls?

Answer: Concrete blocks are larger in size and lighter than fired clay bricks. Blocks offer faster installation and better thermal properties but require careful handling to prevent damage to edges. Brick walls have smaller units and offer more flexibility in design and finish.

Question: What tests are performed on plaster?

Answer: Field checks include measuring thickness with a depth gauge and tapping the surface to detect hollows. Samples can be taken for compressive strength tests if specified. Visual inspection of smoothness and absence of cracks is also important.

Question: How can I avoid cracks in plaster?

Answer: Use properly graded sand, maintain correct water–cement ratio, apply plaster in thin coats, and cure the plaster for at least seven days. Avoid applying plaster on excessively hot or windy days.

Question: What is the role of a quantity surveyor in masonry works?

Answer: Quantity surveyors measure the quantity of bricks, blocks and plastering in the bill of quantities, prepare rate analysis for materials and labour, check contractor bills and variations, and ensure that material wastage is within allowable limits.

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