Construction Technology and Environmental Services L1-3

Question 1

WHAT IS SUBSTRUCTURE?

Answer 1

All works undertaken beneath the damp proof course, providing the basis for the superstructure.

Question 2

WHAT IS EXTERNAL ENVELOPE?

Answer 2

Materials and components forming the external shell of a building.

These may be load bearing or non-load bearing.

Question 3

WHAT ARE THE BUILDING REGULATIONS?

Answer 3

Statutory instruments which set the minimum performance standards for design and construction of buildings.

Supported by Approved Documents and other codes of practices, i.e. BRE Digests.

Question 4

WHAT ARE THE APPROVED DOCUMENTS?

Answer 4

A. Structure
B. Fire Safety
C. Site Preparation and damp proofing
D. Toxic substances
E. Soundproofing
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
O. Overheating
P. Electrical safety
Q. Security in dwellings
R. Infrastructure for electronic communications
S. Infrastructure for charging electric vehicles
7. Materials & workmanship

Question 5

WHAT ARE BRITISH STANDARDS?

Answer 5

Publications issued by British Standards Institution prefixed BS.

Minimum standards for materials, components, design and construction of buildings.

Question 6

WHAT ARE INTERNATIONAL STANDARDS?

Answer 6

Publications issued by the International Organisation for Standards prefixed ISO.

They are compatible with and complement the British Standards.

Question 7

WHAT IS SUPERSTRUCTURE?

Answer 7

All internal and external elements above the damp proof course, made up of:

• External walls
• Stairs
• Roof
• Structural walls
• Suspended ceilings
• Raised floors

Question 8

WHAT ARE THE TYPICAL COMPONENTS OF SITE INVESTIGATION?

Answer 8

To collect and record data to assist with the design and construction process. This should include matters that may impact the development, such as:

• Boundary hedges & fencing
• Existing trees
• Size, depth and location of services inc. gas, telephone, electricity, water and drainage.
• Existing buildings
• Ground water conditions
• Soil investigations
• Trial pit information

Question 9

WHAT IS THE PURPOSE OF SOIL INVESTIGATIONS?

Answer 9

To determine the suitability of the site for the proposed works, determining adequate and economic foundation design.

To determine potential difficulties associated with the ground conditions, i.e. contaminated or easily eroded, to identify a suitable foundation solution.

Question 10

WHAT ARE THE MAIN SITE CONSIDERATIONS?

Answer 10

• Access
• Storage
• Accommodation / welfare
• Temporary services
• Plant
• Fencing & hoarding
• Health & Safety risks

Question 11

WHAT IS A RETAINED FACADE?

Answer 11

The facade of the building is retained whilst everything behind the front wall is demolished.

Allowances for temporary support structure and cleaning and restoration works are required.

Often required as a result of listed building requirements.

Question 12

WHAT ARE TEMPORARY WORKS?

Answer 12

Temporary works do not usually appear on construction drawings but may be required dependent on method of construction being used.

May be required as a Health and Safety requirements, e.g. temporary propping.

Question 13

WHAT IS A TOWER CRANE AND WAHT ARE SOME CONSIDERATIONS DURING ITS ERECTION AND OPERATION?

Answer 13

Tall crane used for lifting objects into high place, the boom allows longer reach with 360 degree access.

Longer boom reduces payload capacity.

Smaller cranes are used to erect tower cranes.

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

Question 14

WHAT IS A SCAFFOLD?

Answer 14

Temporary working platform erected to the perimeter of a building, providing a safe working space at a convenient height.

Scaffold is usually required for works 1.5m above ground level.

Question 15

WHAT IS SHORING?

Answer 15

Shoring is a form of temporary support given to existing building when in danger of collapse during repairs / alterations.

To provide 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

Used for soil investigations or geothermal heating solutions.

Boreholes are the most suitable method of soil investigation beyond 3m depth.

Geothermal boreholes are permanent, using Earth’s natural heat to raise the temperature of circulated water. This is a closed system, used to heat buildings above as a sustainable technology.

Question 18

WHAT ARE PILES?

Answer 18

Series of columns inserted into the ground to transmit the load of a structure to lower in the subsoil.

Used where no suitable foundations conditions are present near ground level, or if the water table is high.

Question 19

WHAT ARE THE DIFFERENT TYPES OF PILES?

Answer 19

Sheet piles:
- A deep trench is excavated and concrete is poured in situ, used to form basement walls or act as retaining walls.

Secant piles:
- Interlocking piles (male and female, different diameters and hardness) bored to provide a combination of foundations and basement walls.
- Provide a waterproof structure and are a top down construction method.

Bored piles:
- An auger is used to excavate the soil and concrete is poured in once complete.

Pre-cast piles:
- Piles are hammered into the ground, not often favoured due to noise levels associated with installation and lack of flexibility in terms of depth required.

Question 20

WHAT ARE THE DIFFERENT WAYS THE PILES TRANSFER THEIR LOAD TO THE SURROUNDING GROUND?

Answer 20

End bearing piles - Transfer load through low bearing capacity soil to a strong stratum such as rock or very dense mud.

Friction piles - Bear on frictional resistance between their outer surface and the soil in contact.

Settlement reducing piles - Incorporated beneath the centre of raft foundations in order to reduce differential settlement to an acceptable level.

Tension piles - Resist uplifting forces causing movement such as hydrostatic pressure, seismic activity or overturning movement.

Question 21

WHAT IS THE DIFFERENCE BETWEEN BORED VS. PRE-CAST PILES?

Answer 21

Bored piles:
- The process for removing the spoil to form the hole is carried out by a boring technique.
- Used primarily in cohesive soils to form friction piles and when forming pile foundations close to existing buildings as noise and vibration is limited.

Pre-cast piles:
- Used where soft soil deposits overlie firmer strata, driven using a drop or single action hammer.
- Issues can arise over noise levels associated with installation of pre-cast piles.

Question 22

WHAT ARE THE PROBLEMS TO PQS REGARDING COST CONTROL WITH PILING AND WHO OWNS THE RISK?

Answer 22

Pile depth is never certain and the procurement route used determines who takes the risk.

For example, under traditional or D&B procurement the Contractor would take risk, however under Management Contracting the risk remains with the Employer.

Question 23

WHAT IS A RAFT FOUNDATION?

Answer 23

Raft foundations are the most popular type of raft, one solid, reinforced concrete slab.

Raft foundations spread the load of the superstructure over a large base, reducing load per m2 of the area.

Useful in low bearing capacity soil, e.g. silts / clay.

They can be solid raft slab or beam and slab raft such as a ground beam system and suspended PC concrete ground floor.

Beam and slab raft foundations have beams and thick edges, increasing strength (heavier loads of walls and columns).

Question 23

WHAT IS A STRIP FOUNDATION?

Answer 23

Strip foundations are formed by creating a shallow continuous excavation to support the perimeter and internal walls.

They are referred to as strip footings and are suitable for most subsoils and a light structural design.

Question 24

WHAT ARE PAD FOUNDATIONS?

Answer 24

Provide a base for reinforced concrete / steel columns.

Formed by making an isolated excavation in the shape of a square / rectangle.

Usually have reinforcement mesh installed within and spread the load to a layer of bearing soil or rock below.

Question 24

UNDER WHAT CONDITIONS WOULD YOU EXPECT A RAFT FOUNDATION TO BE USED FOR A SUBSTRUCTURE?

Answer 24

Used for lightly loaded buildings on sites with poor soils.

Heavy loads have potential to cause movement sideways as a result of rafts not being very deep.

Question 25

WHAT ARE RETAINING WALLS?

Answer 25

Act as an earth retaining structure for part or all of their height.

Used to support and retain soils laterally so it can be retained at two different levels on two sides.

Question 26

WHAT ARE THE MAIN TYPES OF EXCAVATION FOR FORMING BASEMENTS?

Answer 26

Open excavations that use battered excavation sides which are cut back to a safe angle, eliminating the need for temporary earth work support. This requires additional excavation costs and significant working space when compared to other methods.

Perimeter Trench Excavation requires earthwork support with the basement walls being constructed, then the inside of the basement excavated.

Complete Excavation - firm subsoils only. The basement is excavated from the centre first and basement slab cast while the sides of the excavation are supported by struts.

Question 27

WHAT IS A BASEMENT?

Answer 27

A storey constructed below ground level.

Question 28

WHAT ARE THE 3 DIFFERENT TYPES OF BASEMENT CONSTRUCTION?

Answer 28

(1) Retaining wall and raft consists of slab raft foundation serving as basement floor to distribute the load. The basement walls serve as retaining walls.

(2) Box and Cellular, similar to above, however internal structural walls are used to transfer and spread loads over the raft and divides the basement into cells.

(3) Piled solution where the main superstructure loads are carried to the basement floor by columns and transmitted to the ground via pile caps and bearing piles. In this example, the basement has numerous columns passing through it.

Question 29

WHAT ARE BEARING PILES?

Answer 29

End bearing piles develop most of their load-bearing capacity at the toe of the pile, bearing on dense soil or a hard layer of rock.

The pile transmits through soft, compressible strata onto firm strata, alike superstructure columns continued.

Question 29

WHAT ARE PILE CAPS?

Answer 29

A dense mat-like structure that rests on the pile, increasing the stability of the structure.

Used to cover the top of dock pilings to protect from water ingress and damage.

Question 29

WHAT ARE THE 3 MAIN METHODS OF WATERPROOFING A BASEMENT?

Answer 29

(1) Dense Monolithic

(2) Tanking

(3) Drained Cavity

Question 30

WHAT IS DENSE MONOLITHIC BASEMENT WATERPROOFING?

Answer 30

Dense Monolithic:

• Two piece rather than usual three piece construction - the floor and footings are poured simultaneously, then the walls built atop.
• Designed and built to form a watertight space using high quality reinforced concrete, requiring good workmanship and strict control.
• Success is dependent on the cement to water ratio and degree of compaction. Joints also need to be carefully designed.