Construction Technology

Question 1

What is substructure?

Answer 1

All structure below the superstructure i.e. all structure below ground level including the ground floor bed

Question 2

What is superstructure?

Answer 2

All internal and external structure above the substructureMade up of primary (ext walls, stairs, roof, structural walls) and secondary (suspended ceilings / raised floors, balustrades, doors) elements and finishes (tiles, paint, stair nosings)

Question 3

What is the external envelope?

Answer 3

The materials and components that form the external shell or enclosure of a buildingMay be load or non–load bearing

Question 4

What are the Building Regulations?

Answer 4

Statutory instruments that sets out the minimum performance standards for the design and construction of buildingsSupported by the Approved Documents A to P and other codes of practice

Question 5

25). Name some key sections of the CLG (Department for Communities and Local Government) Building Regulations 2010?

Answer 5

– 2.1 Part A: Structure
– 2.2 Part B: Fire safety
– 2.3 Part C: Site preparation and resistance to contaminants and moisture.
– 2.4 Part D: Toxic substances.
– 2.5 Part E: Resistance to the passage of sound.
– 2.6 Part F: Ventilation.
– 2.7 Part G: Sanitation, hot water safety and water efficiency.
– 2.8 Part H: Drainage and waste disposal.
– 2.9 Part J: Heat producing appliances and Fuel storage system.
– 2.10 Part K: Protection from falling, collision and impact.
– 2.11 Part L: Conservation of fuel and power.
– 2.12 Part M: Access to and use of buildings.
– 2.13 Part N: Glazing – Safety in relation to impact, opening and cleaning.
– 2.14 Part P: Electrical safety.
– 2.15 Part Q: Security – Dwellings.
– 2.16 Part R: Physical infrastructure for high–speed electronic communication networks. – 2.17 Regulation 7: Materials and workmanship. – 2.18 Procedure

Question 6

What are the approved documents?

Answer 6

StructureFire safetySite preparationToxic substancesSound resistanceVenitationHygieneDrainage and waste disposalHeat producing appliancesProtection from falling, collision and impactConservation of fuel and powerDisabled access and facilitiesGlazingElectrical safety

Question 7

What are British Standards?

Answer 7

Publications issued by the British Standards Institution – prefixed BSThey give recommended min standards for materials, components, design and construction practices

Question 8

What are the typical components of site investigations?

Answer 8

Objective is to systematically collect and record data to help in design / constructionShould include anything on adjacent sites that may impact and:Boundary hedges / fencingExisting treesSize, depth and location of services – gas, telephone, electricity, water, drainsExisting buildingsGround water conditionsSoil investigations – trial pits etc

Question 9

What are international standards?

Answer 9

Prepared by the International Organisation for Standardisation – prefixed ISOCompatible with and complement BS’s

Question 10

Tell me more about soil investigations?

Answer 10

Purpose is to determine the suitability of the site for the proposed works and determine adequate and economic foundation designShould determine the potential difficultiesThe method chosen will depend on type of building – function, size etc

Question 11

What are the main site considerations?

Answer 11

Access considerations – approach roads etcStorage considerationsAccommodationTemporary servicesPlantFencing / hoardingSafety and health

Question 12

What is a retained façade?

Answer 12

The facade of the building is retained whilst everything behind the front wall is demolished.Allowance needs to be made for a temporary support structure and also cleaning/ restoration works to the retained façade. Often listed.

Question 13

What are temporary works?

Answer 13

Temporary works do not normally appear on construction drawings but demonstrate methods that might be appropriate and resources necessary to ensure safe construction i.e. propping.

Question 14

What is landfill tax?

Answer 14

Landfill Tax was brought in by the Government on 1 October 1996, to help reduce the amount of waste landfilled in the UK and to promote the reuse and recycling of waste, and research into waste practices.The tax, administered by HM Customs & Excise, applies to all waste disposed of, at a licensed landfill site, unless specifically exempt.

Question 15

At what rates is landfill tax charged?

Answer 15

Landfill Tax is charged at 2 rates:£2 per tonne for all inert waste£38 per tonne for all other taxable waste

Question 16

What is a tower crane and how do you erect one? What would stop a tower crane from working?

Answer 16

A tower crane is a tall crane used for lifting objects into high places. The boom allows a longer reach with 360 access. A longer boom reduces the payload capability.You would usually use a smaller crane to erect a tower craneWeather conditions could prevent it from working, in particular high, strong winds.

Question 17

What is a scaffold?

Answer 17

Temporary working platform erected around the perimeter of a building or structure to provide a safe working place at a convenient heightUsually required for work above 1.5m above ground

Question 18

What is shoring?

Answer 18

Form of temporary support given to existing buildingsPurpose is to provide a precaution against damage or injury for collapse of structure

Question 19

What are hoists?

Answer 19

Designed for the vertical transportation of materials or people

Question 20

What is a foundation?

Answer 20

Function is to safely sustain and transmit to the ground on which it rests the combined dead, imposed and wind loads of the structure

Question 21

What are the main components of concrete?

Answer 21

Cement, aggregate (natural rock, crushed stone, gravel) and water

Question 22

What is a borehole?

Answer 22

A borehole can be used for soil investigation or for geothermal heating solutions.Boreholes are the most suitable method of soil investigation when foundations are over 3m deepGeothermal boreholes are permanent boreholes that use the Earth’s natural heat to raise the temperature of circulated water. This is a closed system and can be used to heat the building above. It’s seen as a sustainable technology.

Question 23

What are piles?

Answer 23

A series of columns constructed or inserted into the ground to transmit the load of a structure to a lower level of subsoilUsed where no suitable foundations conditions near ground level or high water table

Question 24

What are sheet piles?

Answer 24

Sheet piles – a deep trench is excavated and concrete is poured in situ. The piles can be used to form basement walls or act as retaining walls.

Question 25

What are secant piles?

Answer 25

Secant piles – interlocking piles (male and female, often different diameters and hardness) are bored to provide a combination of foundations and basement walls. They go someway in providing a waterproof structure. Secant piles are often seen when a top down construction method is used.

Question 26

What are bored piles?

Answer 26

Bored Piles – an auger is used to excavate the soil and then concrete is poured in once complete. A variation to this is CFA (Continuous Flight Augered) where the piles are bored, Bentonite slurry is pumped in to stop the core collapsing and then concrete (which is denser than Bentonite) is poured in. Bentonite is environmentally harmful and is not C21st.

Question 27

What are pre–cast piles?

Answer 27

Pre–cast piles – pre–cast piles are brought to site and hammered into the ground. Not often favoured due to the high noise levels associated with installation and the lack of flexibility in terms of depth required.

Question 28

What are the different ways that the piles transfer their load to the surrounding ground?

Answer 28

End bearing piles
Friction piles
Settlement reducing piles
Tension piles – tall chimneys, transmission towers and jetties
Laterally loaded piles – bridge piers, trestles to overhead cranes, tall chimneys and retaining walls

Question 29

What is the difference between bored/pre–cast piles?

Answer 29

Bored piles remove the spoil to form the hole by a boring technique. Used in cohesive subsoils forming friction piles and when close to existing buildings where the allowable amount of noise and/or vibration is limited.Pre–cast Concrete piles are used where soft soil deposits overlie firmer strata. These piles are driven using a drop or single action hammer.

Question 30

What are the problems to the PQS regarding cost control with piling? Whose risk is the piling?

Answer 30

The end depth of the piles are never a certainty and the procurement route used determines who takes the risk (traditional/ D&B = the main contractor; management contracts = employer)

Question 31

What is a raft foundation?

Answer 31

Used to spread the load of the superstructure over a large base and reduce the load per m2 of the area
Useful in low bearing capacity soils and heavy individual column loads
Can be a solid raft slab or beam and slab raft – ground beam system and suspended PC concrete ground floor

Question 32

Under what conditions would you expect a raft foundation to be used for a substructure?

Answer 32

A raft can be used for lightly loaded buildings on sites with poor soils
Heavy loads to the raft have the potential to cause the raft to move sideways as a result of raft foundations not being very deep.

Question 33

What is a strip foundation?

Answer 33

Suitable for most subsoils and a light structural design, usually reinforced

Question 34

What are pad foundations?

Answer 34

Provide a base for reinforced concrete or steel columns

Usually constructed from reinforced concrete

Question 35

What are retaining walls?

Answer 35

They act as an earth retaining structure for the whole or part of their heights
Need to consider water pressure and pressure of the retained earth in their design

Question 36

What are the main types of excavation?

Answer 36

Open – use battered excavation sides cut back to a safe angle (no temp. supports), can easily construct basement walls BUT extra excavation costs and need a lot of free site spacePerimeter Trench Excavation – trench dug wide enough to form basement walls, support as required – basement walls are constructed then the inside of the basement is excavated.Complete Excavation – used in firm subsoils. The Centre of the basement is excavated first, then the basement slab cast while the sides of the excavation are supported by struts

Question 37

What is a basement?

Answer 37

A storey below the ground storey

Question 38

What are the 3 different types of basement construction?

Answer 38

Retaining wall and raft (monolithic) – slab raft foundation (basement floor) that distributes the load, basement walls are retaining wallsBox and Cellular raft – Like above but internal structural walls spread load over the raft, divides basement into cellsPiled – load is carried to the basement floor by columns and transmitted via pile caps and bearing piles (basement has columns in it)

Question 39

What are the main methods of waterproofing a basement? (part A)

Answer 39

Dense monolithic – this is where the basement is designed and built to form a watertight space using high quality reinforced concrete, needs good workmanship and strict control. Success will depend on water / cement ratio and degree of compaction. Joints need to be carefully designedTanking – e.g. asphalt, polythene sheeting, bitumen, epoxy resins. These can be applied internally or externally to provide a continuous membrane to the base slabs and walls. Externally is better as it protects the structure as well.

Question 40

What are the main methods of waterproofing a basement? (part B)

Answer 40

Drained Cavity – can be used for new or refurbishment work. It accepts a small amount of water seepage will occur, and collects and drains this away. Builds an inner non–load bearing wall to form a cavity. The floor is laid to falls, moisture drains to a sump and is discharged direct or pumpedN.B. Basements are rated as to their final use e.g. habitable, plant, storage and the waterproofing solution is often influenced by this.

Question 41

What is scabbling?

Answer 41

Scabbling utilizes piston driven carbide tipped heads which impact the surface at a rapid rate pulverizing concrete or brittle coatings. Scabbling can be very effective in the removal of slightly bonded coatings or where the coatings are impossible to be removed by the shot blasting process. It can also remove level inconsistencies in concrete floors

Question 42

What are the technical advantages of steel frames?

Answer 42

Quick to assemble,100% recyclable – inorganic – will not warp, split, crack or creep –Highest strength to weight ratio of any building material –Not vulnerable to termites or any type of fungi or organism Dimensionally stable – does not expand or contract with moisture or temperature changes.Consistent material quality – produced in strict accordance with national standards, no regional variationsLight steel components are always straightSteel is non–combustible so it will not contribute to the spread of a fire.Lighter therefore poor soil conditions will need steel over concrete

Question 43

What are the technical disadvantages of steel frames?

Answer 43

Needs fire protectionParts may need replacingPrice of steel is variableNeed experienced builders – additional costEven though steel components will not burn they will actually fail (collapse) before a wood component in a fire.

Question 44

What are the technical advantages of concrete frames?

Answer 44

Examining the impact of the steel price rises has found that the whole project costs for concrete framed buildings are marginally less than for steel framed buildings.Fire protection as part of structureSlower form of construction at this early stage will reduce the cash flow early onMaintenance of an insitu concrete frame is lowCladding can be fixed to it and replaced easily. It also provides good sound and heat insulation. Insitu allows for alteration at late stage of constructionCan deal with complex geometry better than steelwork

Question 45

What are the technical disadvantages of concrete frames?

Answer 45

More time consuming. Slower to constructEdges may not be as square and surfaces not as flat as steelThe need for steel reinforcement leads to some of the cost issues associated with steelHeavier so requires larger foundations

Question 46

What are the different parts of a steel beam?

Answer 46

A simple I Beam is made up:Flange (Top and Bottom of the vertical steel)Web, which is the vertical steel part of the IRoot, which is where the Flange and the Web join.

Question 47

What is a Steel Table?

Answer 47

They provide standard information on steel sections in a tabulated form. For each serial size and Universal beam number.

Question 48

What is the weight of steel?

Answer 48

1 cubic inch of steel weight .283 lbs.10mm cubed of steel weight is 0.0078kg

Question 49

What is powder coating?

Answer 49

A tough durable factory applied organic coating on metals, such as aluminium or galvanized steel, available in many colours.E.g. polyester, polyurethane, acrylic, and epoxy which are sprayed on, followed by heat curing to give a film thickness of 50 to 100micorns.Any holes should be made and any cutting done before the coating is applied.

Question 50

What is an RHS / SHS?

Answer 50

RHS = Rectangular Hollow SectionSHS = Square Hollow Section

Question 51

What is intumescent paint? How do you apply intumescent paint?

Answer 51

Fire Resistant paint, sprayed on in the factory. Touched up by hand on site.

Question 52

What are connections (in relation to steel) and what percentage would you expect them to be?

Answer 52

Plates, bolts or welding. Usually 5% by weight.

Question 53

What is an upstand?

Answer 53

A vertical strip or skirting, such as the weatherproofing where roofing meets an abutment wall. It can be the roofing itself, particularly for mastic asphalt, the top part of a one–piece apron flashing, a mortar skirting or an upstand flashing, and either stepped, raking or level.

Question 54

What is power floated and why?

Answer 54

Concrete is power floated in order to maintain a flatter surface of lightweight concrete that has been applied at a faster rate i.e. in commercial offices.

Question 55

What is post tensioned concrete?

Answer 55

This method is usually employed where stressing is to be carried out on site after casting an insitu component or where a series of pre–cast concrete units are to be joined together to form the required member. In post–tensioning, concrete is cast around ducts or sheathing in which the tendons are to be housed. Stressing is carried out after the concrete has cured by means of hydraulic jacks operating from one of both ends of the member.

Question 56

What is formwork?

Answer 56

Anything that holds fresh in–situ concrete in place until it hardens, such as plywood shutters, steel pan forms, fibreglass moulds or profiled decking, as well as its supporting props, centering or falsework, plus accessories like wedges and clips for tightening joints and to make stripping easy.

Question 57

What is slip forming?

Answer 57

A method for constructing a repetitive structure such as a core, lift shaft or stairwell. The formwork is constantly moving upwards, approx. 1” every 10mins.The concrete that becomes exposed must be cured enough to support.

Question 58

What is jump forming?

Answer 58

Jump forming is where a significant height of concrete is cast and left to cure.The whole formwork module is then moved up and repeated.It works in a similar principle to slip forming but is slower and cheaper in process terms.

Question 59

What is an A182 mesh?

Answer 59

The mesh used to reinforce concrete slabs (generally). The mesh is laid down and the concrete poured over it.

Question 60

In a brick/block cavity wall, how are window openings dealt with in terms of closing the cavity, preventing water penetration and structurally?

Answer 60

Cavity Tray – A damp proof course that crosses the 50mm wide cavity of a cavity wall, stepping up at least 150mm between the outer and inner leaves, to form a gutter that leads to a weephole in the outer leaf. DPC – (Damp Proof Course) – A strip of impervious material the same width as brickwork or blockwork wall to stop moisture rising from the ground up the external leaf.Structurally: Lintel – A small beam over a window/door head to carry a wall load only.

Question 61

What is the size of a brick?

Answer 61

Standard bricks are 215mm x 102.5mm x 65mm

Question 62

What is the frog and which side does it go on?

Answer 62

The frog is an indentation in one of the bed faces of a brick, usually the top.Bricks with two frogs are known as ‘double–frogged’, though these are less common. Unless specifically stated, bricks should be laid frog (or larger frog) facing up, and with mortar filling the frog.This gives a stronger wall and superior sound insulation.

Question 63

How many bricks are in a m2?

Answer 63

There are about 60 bricks per m2.

Question 64

What are the different types of brick bond?

Answer 64

Stretcher – most common, walls just a half brick wideEnglish – alternating courses of headers and stretchers

Question 65

What is a rain–screen cladding system?

Answer 65

It is a cladding that manages the flow of rainwater on a building. It is not necessarily waterproof itself, but more serves as a screen and protection against rain for the rest of the building.

Question 66

How is composite metal cladding fixed to a steel frame?

Answer 66

BoltedRivetedWelded.

Question 67

What other elements will be affected by the type of cladding systems used?

Answer 67

FrameRoofM&E.

Question 68

What is an air brick?

Answer 68

A perforated brick to allow for ventilation into a room or an underfloor space. NOT a weep hole.

Question 69

What are the factors that might affect the choice materials for internal partitions?

Answer 69

Fire rating requirements,Restriction for noise (Db rating),Visually – Opaque/TransparentFixed or movableStrength – If anything is to be fixed to the wall

Question 70

How do you construct a glass partition?

Answer 70

The glass is ‘glazed’ or fixed into a frame, be it either a wooden or a steel frame.The glass is placed in a rebate and secured with putty or beading.This frame is then mounted between the walls / columns required and usually secured with a putty.

Question 71

What are bonded and unbonded types of screed?

Answer 71

Bonded Screeds – Laid on to a ready prepared rough, cleaned concrete baseUnbonded Screeds – Laid on to a sound, clean Bitumen damp proof membrane to BS4483

Question 72

What are floating and resin bonded types of screed?

Answer 72

Floating Screed – Laid with steel or fibre reinforcements on to the insulating board, which in turn can be laid on to a suitable damp proof membrane. Sound, clean prepared base.Resin Bonded Screed – Laid on to a clean, rough pre–prepared concrete base. The resin acts as a ready installed damp proof membrane to the top screed.

Question 73

What is the purpose of a threshold strip?

Answer 73

A lightly rounded metal strip over the joint between the floor finishes or coverings that meet under the door leaf.Prevents fraying, looks better and interrupts combustible flooring under fire doors

Question 74

What are the main components of a hipped end pitched timber roof structure?

Answer 74

The hips” and hip rafters sit on an external corner of the building and rise to the ridge. Where the building has an internal corner, a valley makes the join between the sloping surfaces. They have the advantage of giving a compact, solid appearance to a structure. The roof pitch (slope) may vary.”

Question 75

What are the elements of a flat roof?

Answer 75

Joists – fixed to wall plates to provide supportFurrings – fixed to joists to give required inclineParticle board – fixed to top of furrings to give flat surfaceFelt – 3 layers bonded with bitumen to give waterproof coveringStone chipping – To give protection to felt and to reflect sunlight

Question 76

What are the advantages and disadvantages of the single layer membrane flat roof coverings?

Answer 76

Single layer membrane – one layer of felt consisting of a base sheet of a base sheet of glass fibre or polyester reinforcement impregnated with hot bitumen during manufacture. It is then coated both sides with a weatherproof bitumen compound. It is then dusted with sand on one layer and a thin layer of polythene on the other and left to cool. After cooling it is cut into strips ready for use.Single layer membrane is too thin and are easily punctured are rarely used. But form the cheapest option.

Question 77

What are the advantages and disadvantages of the built–up membrane system flat roof coverings?

Answer 77

Built up felt – is constructed using three layers of the above felt. The first is laid at right angles to the fall commencing at the eaves. The next is laid parallel to the fall and the final layer at right angles. It is then covered with stone chippings.Built up felt is more common but can be easily punctured if proper care is not taken.

Question 78

What are the advantages and disadvantages of asphalt roof coverings?

Answer 78

Mastic Asphalt roofing has an aggregate with a bituminous binder cast block, reheated in cauldrons to 200C, two coats are required.Reduces defects as it is poured on site rather than rolls which can be damaged in transport.Cools quickly, heat close to the roof. 200C is dangerous, proper H&S drills in place. Hard wearing and can design to allow for transit over them. 60–year guarantee on them.

Question 79

What items would you expect to find on a timber or part glazed door that was required to have a half–hour fire rating?

Answer 79

3 hingesIntumescent strip on door or edge of frameSelf–closing deviseIf glazing panel is present it must be 6mm thick, wired glass to a max of 1.2m2 with 13mm x 13mm wood beads encased with non–combustible materials

Question 80

What is an MF ceiling?

Answer 80

Mineral Fibre plasterboard suspended ceiling.

Question 81

What is a metal grid ceiling – what are the benefits?

Answer 81

Suspended ceiling system formed by a square grid.Quicker to construct.Allows for service runs through the void above thus allowing greater floor to ceiling height.Easy access for service/repairsDamaged tiles can be replaced rather than whole ceiling.

Question 82

What is the difference between rolled and tiled carpet tiles and why do we use each type?

Answer 82

Rolled carpets generally better quality and more expensive. Used in dwellings.Carpet tiles – harder wearing, lower quality cheaper and individual tiles can be replaced therefore easier to maintain. Used in offices, hospitals etc. Also where raised flooring systems are used carpet tiles allow for easier access to services that run in the void below.

Question 83

What is top down construction?

Answer 83

“Top down” is used to speed up the construction process of a building with basement levels. The ground floor slab is cast with an access hatch. The ground below is excavated and another slab is formed. If there is another level, the process is repeated. Piles are usually used as foundations and also act as retaining walls. It allows the building above and basement to be constructed at the same time .

Question 84

What is bottom up construction?

Answer 84

“Bottom up” forms the basement and then works upwards in a traditional manner. Simpler but a longer programme.