Construction Technology

Question 1

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

Answer 1

• Lightly loaded buildings on poor soils
• Where underground services i:e train lines dictate the use
• Where it may be impractical to create individual strip or pad foundations for a large number of individual loads. In very general terms, if strip or pad foundations would cover 50% or more of the floor area, then a raft may be appropriate.

Question 2

What are the different types of piling and when would you expect them to be used?

Answer 2

• Sheet piles – These are interlocking sheets (normally steel) that are driven into the ground and are used to form basement walls or act as retaining walls.
• Secant piles – interlocking piles (male and female, often different diameters and hardness) are bored to provide a combination of foundations and retaining walls. They can be used to provide a waterproof structure.
• Rotary Bored Piles (Replacement) – an auger is used to excavate the soil and then concrete is poured in once complete. The reinforced steel is then inserted. CFA (Continuous Flight Augured) is where the boring and pouring takes place simultaneously. Support casing can also be used.
• Pre-cast piles (Displacement) – 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.
• Contiguous piles - A row of successive cast-in-situ concrete piles constructed with unconnected small gaps formed using CFA or rotary bored piles. Quick and easy method for retaining walls.

Question 3

What is the difference between Bored and Pre-cast piles?

Answer 3

Pre-cast piles are hammered into the ground. Advantages:
• Piles of any size, length and shape can be made in advance and used at the site. As a result, the progress of the work will be rapid.
• A pile driven into granular soil compacts the adjacent soil mass and as a result the bearing capacity of the pile is increased.

Bored uses a rotary auger to remove the soil and then replace it with concrete pour in-situ followed by steel reinforcement. Advantages:
• Low noise/impact when working near other buildings
• CFA version is quickest version

Question 4

What are the typical components of site investigations?

Answer 4

Objective is to systematically collect and record data to help in design / construction. Should include:
• Boundary hedges / fencing
• Existing trees
• Size, depth and location of services – gas, telephone, electricity, water, drains
• Existing buildings
• Ground water conditions
• Soil investigations – trial pits etc

Question 5

What are grade 1 basements?

Answer 5

Some leakages and damp areas tolerable. Local drainage may be required. Used in Car parking 
Plant rooms (excluding electrical equipment)

Question 6

What are grade 2 basements?

Answer 6

No water penetration but damp areas tolerable dependent on the intended use. Ventilation may be required to control condensation.
Used in Workshops and Plant rooms requiring drier environment than Grade 1 storage

Question 7

What are grade 3 basements?

Answer 7

Dry environment. No water penetration. Additional ventilation, dehumidification or air conditioning appropriate to intended use Ventilated residential and commercial areas including offices, restaurants, and leisure centres etc

Question 8

What are grade 4 basements?

Answer 8

Totally dry environment. Requires ventilation, dehumidification, or air conditioning appropriate to intended use. Used in Archives, Landmark buildings, and stores requiring a controlled environment

Question 9

What are British Standards?

Answer 9

• Publications issued by the British Standards Institution – (prefixed with ‘BS’)
• They give recommended min standards for materials, components, design and construction practices
• Manufacturers have to pay to have their products and manufacturing processes tested in order to receive BSI Kitemark

Question 10

What are international standards?

Answer 10

• Prepared by the International Organisation for Standardisation – (prefixed ‘ISO’ or ‘EN’ or both)
• Compatible with and complement BS’s using noted with ‘EN’
• In June 2018, it was announced that the UK would apply to stay in the European Standards system for industry products and services after Brexit.

Question 11

Name some forms of modern construction methods?

Answer 11

• Cross Laminated Timber (CLT) – Pre-fabricated boards made of dried timber glued at 90 degrees to the previous layer which reduces movement.
  o High strength to weight ratio
  o Acoustic performance and airtightness performance
• Modular construction – Prefabricated units
  o Speed of supply and installation
  o Reduced cost (labour, waste, economies of scale)
  o Quality control
  o Improved safety
  o Reduced storage requirements
• 3D Printing – Computer-controlled sequential layering of materials to create complex three-dimensional shapes

Question 12

What are the main site considerations?

Answer 12

• Access – approach roads etc
• Storage
• Accommodation
• Temporary services
• Plant
• Site security
• Safety and health

Question 13

What is TM59 (CIBSE Guidance) 2017?

Answer 13

• Standardised assessment method for dynamic thermal modelling of overheating in homes.
To comply with the CIBSE TM59 Overheating Methodology there are criteria thresholds for mechanically and naturally ventilated homes.

• Not compulsory but widely adopted

Question 14

What is a green roof?

Answer 14

Green roofs are roofs that are purposely fitted or cultivated with vegetation. They are also be known as living roofs or eco-roofs.

Extensive – low maintenance
Intensive – More intensive like a garden. May required additional loading capacity

• Decreased surface water runoff
• Decreased heating and cooling demands for the building
• Increased local biodiversity
• Improved local air quality
• Disadvantage - Higher capital cost

Question 15

What is a blue roof?

Answer 15

A blue roof is a roof designed for the retention of rainwater above the waterproofing element of the roof. This is as opposed to more conventional roofs which allow for rainwater to drain from the roof.
• Can be used to reduced water runoff and therefore flooding
• Can be used for rainwater harvesting which can be used to supplement the mains water supply, WC flushing or irrigation of a green roof.

Question 16

What are the advantages and disadvantages of steel frames?

Answer 16

Advantages
• Quicker to construct
• Recyclable
• Strong tensile strength
Disadvantages
• More volatile pricing
• Low compression strength
• Low sound/fire resistance (needs treating)

Question 17

What are the advantages and disadvantages of concrete frames?

Answer 17

Advantages
• High compression strength
• Good noise resistance
• Good fire protection
• Can mould into complex geometry
Disadvantages
• Slower to construct
• Low tensile strength (improved with steel reinforcement)
• High embodied carbon
• Not as square and flat as steel
• Heavy so large buildings require increase foundation cost

Question 18

What are the risks with building basements?

Answer 18

• Risks of flooding due to poor weather
• Poor ground conditions and natural ground heave or settlement.
• Buried structures
• Contaminated soil
• Loads from adjacent buildings and roads
• Failure of waterproofing, insurance and guarantees

Question 19

What is build-ability?

Answer 19

This assesses the design from the perspective of those that will manufacture, install components and carry out the construction works

Question 20

How did the Grenfell tower’s façade contribute to the spread of the fire in 2017?

Answer 20

The ACM (aluminium composite material) rainscreen cladding fitted retrospectively to the original concrete facade had a gap between which allowed a chimney effect for the fire to spread. 
The celotex insulation and cladding were both found to be flammable

Question 21

What is the Hackitt review?

Answer 21

An independent review of the building regulations related to fire safety by Dame Judith Hackitt who was the CEO of the HSE

Question 22

What did the Hackitt review find?

Answer 22

• the roles and responsibilities of those procuring, designing, constructing and maintaining buildings are unclear
• the package of regulations and guidance can be ambiguous and inconsistent
• the processes that drive compliance with building safety requirements are weak and complex with poor record keeping and change control in too many cases
• competence across the system is patchy
• the product testing, labelling and marketing regime is opaque and insufficient; and
• the voices of residents often go unheard, even when safety issues are identified

Question 23

What did the Hackitt review recommend?

Answer 23

• a new Joint Competent Authority (JCA) comprising Local Authority Building Standards, fire and rescue authorities and the Health and Safety Executive to oversee better management of safety risks of high rise residential buildings
• a set of rigorous and demanding roles and responsibilities for “duty holders” (i.e. building owners) to ensure a stronger focus on building safety
• a single, more streamlined, regulatory route to oversee building standards to ensure that enforcement can and does take place where necessary
• clearer rights and obligations for residents to maintain the fire safety, working in partnership with the duty holder
• a package of regulations that is simpler to navigate but genuinely reflects the level of complexity of building work; and
• continuous improvement and best practice learning through membership of an international body.

Question 24

What actions have been taken since the Hackitt review?

Answer 24

• A snap ban was introduced for combustible cladding on all buildings over 18m. This is likely to change to 11m.
• There is also a proposal to introduce sprinklers to all buildings over 11m. The previous law was over 30m.

Question 25

What is CIBSE?

Answer 25

Chartered Institute of Building Service Engineers

Question 26

What is BSRIA?

Answer 26

Building Services Research and Information Association

A non-profit distributing association promoting knowledge and providing specialist services for construction and building services stakeholders

Question 27

Can you describe how you would construct, and measure a piled basement box?

Answer 27

Measure what element?
The piling element would be based on the construction information, the type of piling required, the proposed materials to be used - waterproof concrete etc.

Question 28

Please advise on the different basement types you are aware of?

Answer 28

Type A (Barrier) - Least protection 
Type B (Structurally Integral) - secant Piled Wall / Reinforced Concrete wall to Eurocode wall - waterproof concrete - Middle 
Type C (Drained) - delta systems - Top

Question 29

When would you use a concrete frame

Answer 29

Residential development / tower - quicker / safer - not a big open plan footprint.

Question 30

When would you use a steel frame?

Answer 30

In a warehouse / commercial space - open plan space.

Question 31

What is a transfer slab and why are they used?

Answer 31

A transfer slab is essentially a beam constructed out of concrete and steel reinforcements that is created with a slab of concrete. It is used to transfer the floor loads to the support post and pillars.

Question 32

How would you measure a steel frame and a concrete frame.

Answer 32

Steel on tonnage, concrete on m3. Based on measuring the details and calculating this way.

Question 33

What are the RIBA Stages Of Work

Answer 33

0 - Strategic Definition

1 - Preparation and briefing

2 - Concept Design

3 - Spatial Co-Ordination

4 - Technical Design

5 - Manufacturing & Construction

6 - Handover

7 - Use

Question 34

What are the commonly understood phases of a construction project

Answer 34

1 - Inception - Making the decission to build

2 - Outline Design - Defining outline scope of the clients requirements

3 - Pre Construction - Detailed design, procuerment, appointment of a contractor

4 - Construction

5 - Completion / Handover - Testing, comissioning & explaining / handing the building over to the client

6 - Occupation & use

7 - Decomissioning / demolition

Question 35

What are some of the current legislations & regulations (national & international) in the construction industry & what are their impact

Answer 35

Housing Grants, Construction and Regeneration Act 1996 - Intension is to ensure that payments are made promptly throughout the supply chain and that disputes are resolved swiftly

Local Democracy, Economic Development and Construction Act 2009 (both of which have to do with payment and dispute resolution)

Construction (Design and Management) Regulations 2015 (CDM 2015) - Defines the roles and duties of the client, principal designer, designers and contractors within a construction project to ensure H&S have been recast several times, but finally appear to align with the directive.

• Building Act 1984 and its associated regulations - It’s stated purpose is to “secure the health, safety, welfare and convenience of persons in or about buildings and of others who may be affected by buildings or matters connected with buildings”.
• They set out a list of specific requirements for the construction and alteration of buildings.
• They are subdivided into “dwellings” and “non-dwellings” and are supplemented by a series of approved documents providing guidance on how the requirements of the regulations can be satisfied.
• They also provide for a regime of certification of compliance, including local authorities, approved inspectors and competent person schemes.

The Health and Safety at Work, etc Act 1974 (HSWA) - Is the primary piece of legislation covering occupational health and safety in Great Britain. Sometimes referred to as HSWA, the HSW Act, the 1974 Act or HASAWA. It sets out the general duties which:

• employers have towards employees and members of the public
• employees have to themselves and to each other
• certain self-employed have towards themselves and others

Dame Judith Hackitt’s report following the independent review of building regulations and fire safety made a number of recommendations, including the introduction of a new process into the planning regime, involving a new regulator and “hard stop” gateways for high risk residential buildings, at a point before construction can start, or before they can be occupied.

Covid-19 pandemic guidelines - Led to a raft of legislation, mainly concerned with carrying out construction work in a ”covid-safe” environment, with the various UK (and worldwide) jurisdictions taking different views on many things, such as social distancing, numbers of people gathering, working patterns, protective equipment, travel and transport, vaccination and mandatory isolation.

Structural changes to many pieces of legislation following the UK’s departure from the EU. The UK legislation no longer follows EU law, therefore changes to many pieces of legislation have had to be made as these were originally based on EU directives.