Sri Lanka NVQ L3 Mason flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Respirable crystalline silica

Fine dust from cutting concrete, bricks or stone that reaches deep lung tissue and can cause silicosis; control it with wet cutting, extraction or approved respirators.

Wet cement dermatitis

Prolonged skin contact with wet cement or mortar causes alkaline burns and dermatitis; wear gloves and long sleeves, and wash skin promptly with clean water.

Hearing protection threshold

Hearing protection should be worn when noise exposure reaches 85 dB(A) averaged over an eight-hour day; masonry cutting and grinding commonly exceed this level.

Cement bag storage

Stack cement bags on pallets at least 150 mm off the floor in a dry, ventilated store, keep stacks stable and low, and use the oldest stock first.

Aggregate storage bays

Sand and coarse aggregate are stored on hard, drained surfaces in separate bays with dividing walls so different materials and sizes do not mix or become contaminated.

Underground service check

Before any excavation, confirm the position of buried water, electricity and telephone services from drawings or the utility owner, and hand-dig near marked services.

3-4-5 right angle method

Measure 3 units along one line and 4 along the other, then adjust until the diagonal reads 5 units; any multiple such as 6:8:10 gives a true right angle.

Height of instrument

Height of instrument equals the reduced level of the benchmark plus the backsight; the reduced level of a new point equals the height of instrument minus the foresight.

Diagonal check for square

For a rectangular building, measure both diagonals and adjust the corners until the two lengths are equal; unequal diagonals mean the setting out is not square.

Brick trowel

A flat, diamond-shaped steel blade with a handle used to pick up, spread and trim mortar in brick and blockwork; it is the mason's main laying tool.

Bolster chisel

A wide flat chisel struck with a club hammer to cut bricks and blocks cleanly across a face; wear eye protection because chips fly.

Wheelbarrow capacity

A standard builder's wheelbarrow holds about 60 to 70 litres, that is 0.06 to 0.07 cubic metres, which is used to count loads when batching or transporting concrete.

Spirit level check

Check a spirit level by taking a reading on a flat surface, reversing it end for end and comparing; the bubble must give the same reading both ways.

Mortar mix 1:4

One part cement to four parts sand by volume gives a general-purpose mortar for bricks and blocks; the same gauge box or bucket must be used for every batch.

Mortar usable life

Cement mortar should be used within about two hours of mixing, or one hour in hot weather, before it starts to set; adding water to stiffened mortar weakens it.

Slump test

A cone slump test measures concrete workability in millimetres; a low slump is a stiff mix and a high slump a wet mix, and the test is done soon after sampling.

English bond

Alternate courses of stretchers and headers give a strong wall with no continuous vertical joints; header courses at the quoins need quarter closers to finish correctly.

Bed joint thickness

Standard mortar bed and cross joints are about 10 mm thick, kept between 8 and 12 mm; joints that are too thick reduce wall strength.

Racking back

When a wall is left unfinished, build the end in steps of about 450 mm rather than a vertical straight joint, so the next section can bond into it.

Through stones

Long stones laid across the full wall thickness every 1 to 1.5 metres tie the two faces together and stop a rubble wall from splitting into separate leaves.

Natural bed of stone

Stone is laid on its natural bed, the plane in which it was formed in the quarry, because this orientation gives the greatest strength and resistance to weathering.

Hearting in rubble walls

Small stones and chips packed into the middle of a rubble wall are called hearting; they fill voids and must be well bedded in mortar, not poured in loose.

Scratch coat

The first coat of plaster or render, about 8 to 10 mm thick, is combed or scratched to give a key for the next coat before it sets.

Render thickness

External render is normally built up to 15 to 20 mm in two coats, each coat not more than about 10 to 12 mm thick, to avoid shrinkage cracking.

Curing plaster

New plaster and render should be kept damp for about seven days by light spraying; rapid drying causes shrinkage cracks and weak, dusty surfaces.

Deduction for openings

When measuring masonry, openings larger than the stated limit, commonly 0.5 square metres, are deducted from the wall area; smaller openings are not deducted.

Concrete measurement unit

Concrete is measured and paid for in cubic metres, formwork in square metres, and steel reinforcement in kilograms or tonnes in a bill of quantities.

Waste allowance

Allow roughly 5 to 10 percent extra material for breakage, cutting and spillage; blocks, bricks and tiles need a larger allowance than cement or sand.

Cement bag volume

One 50 kg bag of cement has a loose volume of about 0.035 cubic metres, so roughly 28 to 30 bags make one cubic metre of loose cement.

Toolbox talk

A short briefing, usually five to ten minutes, held at the workplace before work starts; it covers the day's tasks, hazards and controls and lets workers raise concerns.

Near miss reporting

An incident where nobody was hurt but harm was possible must be reported and recorded so the cause can be corrected before a real accident happens.

Method statement

A written document describing the safe sequence, plant, labour and controls for a specific construction task; workers follow it and supervisors check compliance.