NSSCO Building Studies 6186 flashcards

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

Personal protective equipment

Clothing and equipment worn to reduce injury risk on site, including helmet, safety boots, high-visibility vest, eye protection, gloves and dust mask. It is the last defence after eliminating or engineering out the hazard.

Scaffold inspection interval

A scaffold must be inspected by a competent person before first use, after alteration or adverse weather, and at intervals not exceeding seven days. Results are recorded on a tag or register.

Ladder 1 in 4 rule

For every four units of height, the foot of the ladder sits one unit out from the wall, giving an angle of about 75 degrees. Ladders used for roof access extend at least one metre above the landing.

Excavation spoil distance

Spoil, materials and plant are kept at least one metre back from the edge of an excavation to reduce surcharge loading. Trenches deeper than 1.2 m are supported or battered, and gas is tested before entry.

Drawing scale 1:100

One millimetre on the drawing represents 100 millimetres on site, so a 10 m wall measures 100 mm on paper. A 1:50 scale shows the same wall at 200 mm and gives twice the detail.

First-angle projection

An orthographic convention in which the object sits between the viewer and the plane, so the plan is drawn below the front elevation and the side view appears on the opposite side.

Revision cloud

A scalloped line drawn around an altered area of a drawing, usually with a revision letter or number beside it, so readers can see exactly what changed since the previous issue.

Title block contents

The panel on every drawing recording project name, drawing title and number, scale, date, revision status and the author or practice. It controls which version is used on site.

Performance specification

A specification that states the required outcome or standard the finished work must meet, leaving the contractor to choose materials and methods. It contrasts with a prescriptive specification naming exact products.

Bill of quantities

A document listing measured items of work with description, unit and quantity, taken off the drawings and specification. Contractors price each item, and the total forms the tender sum.

Retention

A percentage, commonly five to ten per cent, deducted from each interim payment and held as security. Part is released at practical completion and the balance after the defects liability period.

3-4-5 right angle method

A setting-out technique based on Pythagoras: mark 3 units along one line and 4 along another, then adjust until the diagonal measures 5 units. The corner is then exactly 90 degrees.

Height of collimation

The reduced level of the instrument's line of sight, found by adding the backsight reading to the benchmark level. Subtracting a foresight from it gives the reduced level of that point.

Profile board

A horizontal board set beyond the excavation line on stakes, carrying nails that mark wall faces, centre lines and foundation width. Strings stretched between profiles guide the excavation and brickwork.

Strip foundation width rule

The width of a strip footing is commonly at least three times the wall thickness, and its depth below ground at least one metre or below the frost line, whichever is deeper.

Damp-proof course level

The DPC is built into the wall at least 150 mm above external ground level and laps the damp-proof membrane in the floor, forming a continuous barrier against rising damp.

Raft foundation

A thick reinforced concrete slab covering the whole building footprint, used where soil is weak or variable so loads are spread and differential settlement is reduced.

English bond

A one-brick wall bond with alternating courses of stretchers and headers. It is strong and was traditionally used for thick walls, though it is slower to lay than stretcher bond.

Wall ties spacing

Metal ties connect the two leaves of a cavity wall, fixed at about 900 mm horizontally and 450 mm vertically. The cavity is kept clear of mortar so moisture can drain and ventilate.

Water-cement ratio

The mass of water divided by the mass of cement in a concrete mix. A lower ratio gives higher strength and durability; extra water improves workability but weakens the hardened concrete.

Concrete cover to reinforcement

The depth of concrete between the steel surface and the outside face, typically 25 to 40 mm. Adequate cover protects bars from corrosion and gives fire resistance.

Suspended timber ground floor

A floor of joists spanning between sleeper walls and wall plates, finished with boards, with a ventilated void beneath. Air bricks in the external wall keep the void dry.

Screed

A sand-cement layer, usually 40 to 75 mm thick, laid over a concrete slab to give a level surface for floor finishes. It must cure and dry before tiles or vinyl are laid.

Roof pitch calculation

Pitch is the rise divided by the run, expressed as a ratio or angle. A roof rising one metre over a two metre run has a pitch of 1:2, about 26.5 degrees.

Wall plate

A timber member bedded level on top of the wall to receive the feet of the rafters. It spreads the roof load and is strapped down to resist wind uplift.

Mortise and tenon joint

A joint in which a projecting tenon on one timber fits into a matching mortise cut in another, often fixed with a wooden peg or glue. It resists both pull and sideways force.

Water seal depth

The depth of water held in a trap, about 50 mm, that prevents sewer gas from passing into the building. The trap must be ventilated so the seal is not siphoned away.

Soil stack

The vertical pipe carrying discharge from water closets to the drain. It continues above roof level to ventilate the drainage system and protect trap seals from pressure changes.

Ohm's law and power

Voltage equals current multiplied by resistance (V = I × R), and power equals voltage multiplied by current (P = V × I). These are used to size cables and protective devices.

Cement types

Ordinary Portland cement suits general work, rapid-hardening cement gives early strength for quick striking, and sulphate-resisting cement is used in aggressive ground or marine conditions.

Plaster backing coat mix

The first coat on masonry is commonly a one-to-three or one-to-four sand-cement mix about 10 to 15 mm thick, with a finer finishing coat applied after the backing has set.

Rising damp diagnosis

Moisture rising through a wall because the damp-proof course is missing, bridged or damaged, leaving a tide mark usually under one metre. Penetrating damp and condensation have different patterns.

Break-even point formula

The number of units or jobs needed to cover costs, calculated as fixed costs divided by selling price per unit minus variable cost per unit. Above this point the business makes profit.

Critical path

The longest sequence of dependent activities through a project programme, which sets the shortest possible project duration. Any delay on a critical activity delays the whole project.

Bricks per square metre

For a 222 by 106 by 73 mm brick with 10 mm joints, the module is 235 by 85 mm, giving about 60 bricks per square metre of half-brick wall. Add five to ten per cent for wastage.