CONSTRUCTION TECHNOLOGY & ENVIRONMENTAL SERVICES

Question 1

What is substructure?

Answer 1

• All elements of work that are undertaken below the damp proof course that provides the basis for the superstructure to be constructed upon.

Question 2

What is the external envelope?

Answer 2

• The materials and components that form the external shell or enclosure of a building.
• These may be load or non-load bearing.

Question 3

What are the Building Regulations?

Answer 3

• Statutory instruments that set out the minimum performance standards for the design and construction of buildings.
• Supported by the Approved Documents and other codes of practice.

Question 4

What are the approved documents?

Answer 4

A. Structure.
B. Fire safety.
C. Site preparation and damp proofing.
D. Toxic substances.
E. Sound proofing.
F. Ventilation.
G. Hygiene.
H. Drainage and waste disposal.
I. Not in use.
J. Heating appliances.
K. Protection from falling, collision and impact.
L. Conservation of fuel and power.
M. Disabled access and facilities.
N. Glazing.
O. Not in use.
P. Electrical safety.

Question 5

What are British Standards?

Answer 5

• Publications issued by the BSI prefixed BS.
• Give recommended minimum standards for materials, components, design and construction
  practices.

Question 6

What are international standards?

Answer 6

• Publications issued by the International Organisation for Standardisation – prefixed ISO.
• They are compatible with and complement the British Standards.

Question 7

What is superstructure?

Answer 7

• All internal and external works items above the damp proof course.
• This is made up of:
  o External walls.
  o Stairs.
  o Roof.
  o Structural walls.
  o Suspended ceilings.
  o Raised floors.

Question 8

What are the typical components of site investigations?

Answer 8

• Their objective is to collect and record data to help with the design and construction process. This includes matters in relation to the site that may impact the development for example:
  o Size, depth and location of services including gas, telephone, electricity, water & drains.
  o Existing buildings.
  o Ground water conditions.
  o Soil investigations.
  o Trial pit information.
  o Boundary hedges & fencing.
  o Existing trees.

Question 9

What is the purpose of soil investigations?

Answer 9

• To determine the suitability of the site for the proposed works.
• To determine adequate and economic foundation design and identify a suitable foundation solution.

Question 10

What are the main site considerations?

Answer 10

• Access considerations.
• Storage considerations.
• Accommodation.
• Temporary services.
• Plant.
• Fencing & hoarding.
• Health & Safety risks.

Question 11

What is a retained façade?

Answer 11

• The façade of the building is retained whilst everything behind the front wall is demolished.
• Allowances needs to be made for a temporary support structure and also cleaning & restoration works to the retained façade.
• Retained facades are often required as a result of listed building requirements.

Question 12

What are temporary works?

Answer 12

• Temporary works do not normally appear on construction drawings but may be required depending on the construction methodology being used.
• Temporary works may also be required as a result of health and safety requirements to ensure a safe method of construction for example temporary propping.

Question 13

What is a tower crane and what are some considerations during its erection and operation?

Answer 13

• 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 crane.
• Weather conditions could prevent it from working, in particular high, strong winds.

Question 14

What is a scaffold?

Answer 14

• Scaffold is a temporary working platform erected around the perimeter of a building or structure to
  provide a safe working place at a convenient height.
• Scaffold is usually required for work 1.5m above ground level.

Question 15

What is shoring?

Answer 15

• Shoring is a form of temporary support given to existing buildings.
• Its purpose is to provide a precaution against damage or injury due to collapse of the structure.

Question 16

What are the main components of concrete?

Answer 16

• Cement.
• Aggregate (natural rock, crushed stone, gravel).
• Water.

Question 17

What is a borehole?

Answer 17

• 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 deep.
• Geothermal 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 which is adopted as a sustainable technology.

Question 18

What are piles?

Answer 18

• A series of columns constructed or inserted into the ground to transmit the load of a structure to a
  lower level of subsoil.
• They are used where no suitable foundations conditions are present near ground level or if there is a high water table.

Question 19

What are Sheet piles?

Answer 19

• 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 20

What are Secant piles?

Answer 20

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

Question 21

What are Bored piles?

Answer 21

• An auger is used to excavate the soil and then concrete is poured in once complete.

Question 22

What are Pre-cast piles?

Answer 22

• Piles are and hammered into the ground. This is not often favoured due to the high noise
  levels associated with installation and the lack of flexibility in terms of depth required.

Question 23

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

Answer 23

• End bearing piles - transfer load through low bearing capacity soil to a strong stratum such as rock or very dense sand.
• Friction piles - bear on frictional resistance between their outer surface and the soil in contact.
• Settlement reducing piles - usually incorporated beneath the central part of a raft foundation in order to reduce differential settlement to an acceptable level.
• Tension piles - resist uplifting forces that might otherwise cause the structure to be extracted from the ground due to uplifting forces such as hydrostatic pressure, seismic activity or overturning movement.

Question 24

What is the difference between bored vs. pre-cast piles?

Answer 24

• Bored piles are defined when the process for removing the spoil to form the hole for the pile is carried out by a boring technique.
• They are used primarily in cohesive subsoils for the formation of friction piles and when forming pile foundations close to existing buildings where the allowable amount of noise and/or vibration is limited.
• Pre-cast Concrete piles are generally used where soft soil deposits overlie firmer strata. These piles are usually driven using a drop or single action hammer.
• Issues can arise due to the noise levels associated with the installation method of pre-cast piles.

Question 25

What are the problems to the PQS regarding cost control with piling and who owns the risk?

Answer 25

• The end depth of the piles are never certain and the procurement route used determines who takes the risk.
• For example under a traditional or design & build procurement the main contractor would normally take risk ownership whereas under management contracting the risk would remain with the employer.

Question 26

What is a raft foundation?

Answer 26

• Raft foundations spread the load of the superstructure over a large base and reduce the load per m2 of the area.
• Raft foundation solutions are useful in low bearing capacity soils.
• They can be a solid raft slab or beam and slab raft such as a ground beam system and suspended PC concrete ground floor.

Question 27

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

Answer 27

• 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 28

What is a strip foundation?

Answer 28

• Strip foundations are formed by creating a shallow continuous excavation to support the
  perimeter and internal walls.
• They are also referred to as strip footings and are suitable for most subsoils and a light
  structural design.

Question 29

What are pad foundations?

Answer 29

• Pad foundations provide a base for reinforced concrete or steel columns.
• They are usually formed by making an isolated excavation in the shape of a square or rectangle.
• They often have reinforcement mesh as part of the construction and spread the load to a layer of
  bearing soil or rock below.

Question 30

What are retaining walls?

Answer 30

• They act as an earth retaining structure for the whole or part of their heights.
• They are used to support and retain soils laterally so that it can be retained at different levels on the two sides.

Question 31

What are the main types of excavation for forming basements?

Answer 31

• Open excavations that use battered excavation sides which are cut back to a safe angle. This eliminates the need for temporary earth work support and can be used to construct basement walls. This requires additional excavation costs and significant working space when compared to other methods.
• Perimeter Trench Excavation can be used to form basement walls. This method requires earthwork
  support with the basement walls being constructed and then the inside of the basement is excavated.
• Complete Excavation can be 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.