ITI/NCVT Mason Building Constructor (AITT Theory) flashcards

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

Safe bearing capacity

The maximum pressure a soil can carry without unacceptable settlement or shear failure, expressed in kN/m2; good soil is about 150-250 kN/m2, soft clay much less.

Slump test

A workability test in which fresh concrete is placed in a standard cone, the cone is lifted and the vertical drop of the concrete is measured in millimetres.

English bond

A masonry bond with alternating header and stretcher courses, giving the strongest traditional bond with no continuous vertical joints through the wall.

Flemish bond

A bond in which each course alternates a stretcher and a header, producing a decorative face pattern that is weaker than English bond in compression.

Queen closer

A brick cut lengthwise into two equal halves, used next to a quoin header to keep the bond pattern correct and avoid a straight vertical joint.

DPC

Damp-proof course: a continuous impervious layer at plinth level, at least 150 mm above ground, lapped 100 mm at joints to stop rising damp.

Reduced level

The height of a point relative to a datum, found on site as height of instrument minus the staff reading (foresight) taken on that point.

Height of instrument

The reduced level of the line of sight of a levelling instrument, calculated as the known reduced level plus the backsight staff reading.

3-4-5 method

A setting-out technique that produces a right angle by forming a triangle with sides in the ratio 3:4:5, or any multiple of those lengths.

Wall tie

A metal tie built into both leaves of a cavity wall at about 450 mm vertical and 900 mm horizontal spacing, sloping outward to drain water.

AAC block

Autoclaved aerated concrete block of about 550-650 kg/m3 density, laid with 2-3 mm thin-bed adhesive and valued for light weight and insulation.

Toothing

The stepped end of a brick wall left for future bonding, formed by leaving one-quarter brick projecting on alternate courses.

Efflorescence

A white salt deposit on masonry caused by soluble salts migrating to the surface with water and crystallising as the water evaporates.

Repointing

Raking out defective mortar joints to 15-20 mm depth, cleaning and wetting them, then refilling with fresh mortar weaker than the masonry.

Curing

Keeping concrete or plaster moist for a set period, at least 7 days for ordinary Portland cement, so that cement hydration continues and strength develops.

Water-cement ratio

The mass of water divided by the mass of cement in a mix; typically 0.45-0.55 for concrete, higher ratios reduce strength and durability.

Mortar grade M

A high-strength cement mortar of about 1:3 cement to sand by volume, giving roughly 10 N/mm2 cube strength at 28 days.

Water retentivity

The ability of mortar to hold its mixing water against suction from absorbent masonry units; low retention causes poor bond and weak joints.

Rise and going

The vertical height of a stair step (rise, typically 150-190 mm) and its horizontal depth (going or tread, typically 250-300 mm).

Rise of an arch

The vertical distance from the springing line to the crown; a semicircular arch has a rise equal to half its span.

Lintel bearing

The length of a lintel that rests on the masonry each side of an opening, normally 100-150 mm, to transfer the wall load safely.

Plinth area estimate

A preliminary cost estimate found by multiplying the plinth area of the building by a standard rate per square metre for that class of construction.

Dry volume factor

The multiplier of about 1.30-1.33 applied to the wet volume of mortar to allow for bulking of sand and voids between particles.

Brick count per cubic metre

About 500 standard modular bricks (190 x 90 x 90 mm) make one cubic metre of brickwork when 10 mm mortar joints are included.

Fall protection threshold

Guardrails, nets or harnesses are required for work at heights of 1.8 m or more; a guardrail has a top rail at 1.0 m and a toe board.

Permit to work

A written authorisation required before high-risk tasks such as hot work, confined-space entry or work at height, listing hazards and controls.

Tool-box talk

A short briefing held before work begins, covering the task sequence, hazards, control measures and any changes since the last briefing.

Vitrified tile

A tile with water absorption below 0.5 percent, very dense and frost resistant, requiring a suitable adhesive rather than a thick mortar bed.

Skirting

The finishing strip at the base of an internal wall, typically 100-150 mm high, protecting the plaster and covering the floor junction.

Slenderness ratio

The effective height or length of a wall divided by its thickness; for unreinforced masonry the limit is about 27.

Buttress

An external pier built against a wall, often with a battered face, to resist lateral thrust from roofs, arches or retained earth.

Seasoning of timber

Drying timber to a moisture content of about 12-15 percent so that it shrinks and warps before use, not after installation in shuttering or joinery.

Spirit level

A tool with a sealed bubble vial, typically 600 mm long, whose bubble centred between the lines shows that a surface is horizontal or vertical.