Construction Technology & Environmental Services Flashcards
What is substructure?
All elements of work that are undertaken below the damp proof course that provides the basis for the superstructure to be constructed upon.
What is the external envelope?
The materials and components that form the external shell or enclosure of a building.
These may be load or non-load bearing.
What are the Building Regulations?
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.
What are the approved documents?
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.
S.
What are British Standards?
Publications issued by the British Standards Institution prefixed BS.
They give recommended minimum standards for materials, components, design and construction practices.
What are international standards?
Publications issued by the International Organisation for Standardisation – prefixed ISO.
They are compatible with and complement the British Standards.
What is superstructure?
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.
What are the typical components of site investigations?
Their objective is to collect and record data to help with the design and construction process. This
should include matters in relation to the site that may impact the development for example:-
o Boundary hedges & fencing.
o Existing trees.
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.
What is the purpose of soil investigations?
Their purpose is to determine the suitability of the site for the proposed works and determine adequate
and economic foundation design.
The investigation should determine the potential difficulties associated with the ground conditions and
assist with identifying a suitable foundation solution.
What are the main site considerations?
• Access considerations.
• Storage considerations.
• Accommodation.
• Temporary services.
• Plant.
• Fencing & hoarding.
• Health & Safety risks.
What is a retained façade?
The facade 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.
What are temporary works?
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.
What is a tower crane and what are some considerations during its erection and operation?
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.
What is a scaffold?
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.
What is shoring?
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.
What are the main components of concrete?
• Cement.
• Aggregate (natural rock, crushed stone, gravel).
• Water.
What is a borehole?
• 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.
What are piles?
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
What are the different types of piles?
Sheet piles.
o A deep trench is excavated and concrete is poured in situ.
o The piles can be used to form basement walls or act as retaining walls.
Secant piles.
o Interlocking piles (male and female, often different diameters and hardness) are bored to
provide a combination of foundations and basement walls.
o They support in providing a waterproof structure and are often seen when a top down
construction method is used.
Bored Piles.
o An auger is used to excavate the soil and then concrete is poured in once complete.
Pre-cast piles.
o 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.
What are the different ways that the piles transfer their load to the surrounding ground?
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.
What is the difference between bored vs. pre-cast piles?
• 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.
What are the problems to the PQS regarding cost control with piling and who owns the risk?
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.
What is a raft foundation?
• 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
Under what conditions would you expect a raft foundation to be used for a substructure?
• 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.
What is a strip foundation?
• 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.
What are pad foundations?
• 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.
What are retaining walls?
• 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.
What are the main types of excavation for forming basements?
• 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.
What is a basement?
A storey constructed below ground level.
What are the 3 different types of basement construction?
• Retaining wall and raft which consists of a slab raft foundation to serve as the basement floor that
distributes the building load. The basement walls serve asthe retaining walls.
• Box and Cellular raft which is similar to above however the internal structural walls are used to transmit
and spread loads over the raft and divides the basement into cells.
• 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.
What are the 3 main methods of waterproofing a basement?
• Dense monolithic where the basement is designed and built to form a watertight space using high
quality reinforced concrete. This requires good workmanship and strict control. Success depends on
the water to cement ratio and the degree of compaction. Joints also need to be carefully designed
• Tanking using materials such as asphalt, polythene sheeting, bitumen and epoxy resins. These can be
applied internally or externally to provide a continuous membrane to the base slabs and walls. External
application is better as it protects the structure in addition to the waterproofing.
• Drained Cavity solutions can be used for new or refurbishment work. This allows a small amount of
water infiltration to occur. The water is collected and then drains away to a sump or is directly
discharged using a pump.
What is scabbling?
• Scabbling utilises piston driven carbide tipped heads which impact the surface material at a rapid rate.
• This pulverises concrete or brittle coatings and 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.
What are the technical advantages of steel frames?
• Steel frames are often quicker to assemble in comparison to alternative methods.
• They are 100% recyclable and inorganic meaning they will not warp, split, crack or creep.
• They offer the highest strength to weight ratio of any building material.
• Steel frames are not vulnerable to termites or any type of fungi or organism.
• They are dimensionally stable and do not expand or contract with moisture or temperature changes.
• Due to strict manufacturing controls, consistent material quality can be obtained due to production taking place in line with strict standards.
• Steel is non-combustible so it will not contribute to the spread of a fire.
• Steel frames are lighter in comparison to concrete frames and will often benefit from a cheaper foundation solution.
What are the technical disadvantages of steel frames?
• Steel frames require fire protection to be retrospectively installed.
• Fixing components may require replacement over time.
• The price of steel often fluctuates and can result in a lack of cost certainty.
• Installation of steel frames requires experienced builders at an additional cost. Resources can also be difficult to acquire depending on market conditions.
What are the technical advantages of concrete frames?
• Fire protection is often provided inherently as part of the structure.
• Due to offering a slower form of construction in comparison to alternative methods, this will likely result in reduced cash flow expenditure early on in the development.
• Maintenance requirements associated with concrete frames are relatively low in comparison to alternative methods.
• Concrete frames often provide good sound and heat insulation properties in comparison to steel frame
constructions.
What are the technical disadvantages of concrete frames?
• In comparison to steel frames, they are more time consuming to install.
• There may also be complications during the install resulting from colder and inclement weather conditions.
• The need for steel reinforcement can lead to issues around price fluctuations and cost uncertainty associated with steel frames.
• Concrete frames are often heavier and require larger foundations.
Describe a typical Cold Flat Roof Construction
• The void or roof slab is insulated from heat loss from below and is therefore at a colder temperature
than the room below during cold weather.
• Insulation is located above ceiling level.
• Ceiling Joists form the main horizontal members and are fixed to the wall plates.
• Insulation is normally inserted between the roof joists with an air gap or void space being maintained to
allow for cross ventilation.
• There is a risk of condensation forming within the roof void or on the underside of the slab, so good
cross-ventilation is essential.
• Plywood decking is secured on to the joists and finished with the respective roof covering
Describe a typical Warm Flat Roof Construction
• Insulation is placed on top of the roof deck but beneath the waterproof membrane.
• The vapour control layer is usually placed under the insulation.
• This reduces the risk of condensation as the ceiling or roof void is at a similar temperature to the roof.
Describe a typical Inverted Flat Roof Construction
• A roof in which the insulation is placed on top of the waterproof membrane.
• No vapour control is needed.
• The roof void and deck are maintained at similar temperature to the room.
• The insulation protects the membrane from damage but must be anchored down.
Describe a typical parapet wall – roof abutment detail
• The parapet wall or dwarf wall is built along the perimeter edge of the roof.
• The wall height extends above roof level.
• Where the wall intersects with the roof, a flashing or water proofing detail will be required along with a
DPC closer placed above the flashing and at the head of the wall under the coping detail.
Describe a pitched roof detail
• Pitched roofs typically are made up of rafters which span from the apex of the roof and are fixed to the
top of the external wall by a wall plate.
• At the apex of the roof are the ridge tiles which are supported by the ridge board.
• The roof covering whether slate or concrete tiles are typically fixed to roof battens.
• Supporting the rafters and roof coverings are the struts, purlins and roof beams.
• A soffit and eaves board may be fixed to the end of the rafters along with the guttering and rain water goods.
• Vent tiles may also be used to provide natural ventilation to the roof space.
Describe a cladding rainscreen detail
• Rainscreen cladding provides a screening function rather than an enclosure in its own right.
• A rainscreen is used to shield a wall, whether this be of masonry, metal studwork or in some cases glass.
• Usually a rainscreen is designed to permit some controlled leakage with the main functions of resistance
to air and water being provided by the shielded wall behind
Describe a Cladding Stick System
• In the stick system, the curtain wall frame (mullions) and glass or opaque panels are installed and
connected together piece by piece.
• Stick curtain walling systems are versatile and allow for the integration of other systems, such as sliding
doors and windows. They tend to be less specialised and can be built by all types of fabricators as they
are not dependent on having a large factory.
• However, stick systems do require multiple steps to erect and seal the wall, which means more time is
spent on site – an approximate rule of thumb would be that 70% of the work is carried out on site,
with 30% in the factory. This incurs further costs due to additional labour time.
