Construction Technology & Environmental Services Flashcards
What is sub-structure?
All elements of the work that are undertaken below the damp proof cause 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.
They are supported by the Approved Documents and other codes of practice.
What are the Approved Documents?
A - Structure
B - Fire
C - Site Preparation and Damp Proofing
D - Toxic Substances
E - Sound Proofing
F - Ventilation
G - Hygiene
H - Drainage and waste Disposal
J - Heating Appliances
K - Protection from Falling, Collision, and Impact
L - Conservation of Fuel and Power
M - Disabled Access and Facilities
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 Standardization - Prefix ISO.
They are compatible with and complement the British Standards.
What is Superstructure?
- All internal and external works items above the DPC. This is made up of:
- External Walls
- Stairs
- Roof
- Structural Walls
- Suspended Ceilings
- 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:
- Boundary Hedges & Fencing
- Existing Trees
- Size, Depth & Location of Services
- Existing Buildings
- Ground water Conditions
- Soil Investigations
- 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
- Storage
- Accommodation
- Temporary Services
- Plant
- Fencing & Hoarding
- Health & Safety Risks
What is a retained facade?
The facade of a building which is retained whilst the entirety of the building the wall (facade) is demolished.
Allowances need to be made for a temporary support structure, and also cleaning and restoration works to the retained facade.
Retained facades are often required as a result of listed building consents.
What are temporary works?
Temporary works do not usually 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 & safety requirements to ensure a safe method of construction, for example temporary propping.
What is a tower crane and what are the 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 degrees 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 above 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
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 earths 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 a sustainable technology.
What are piles?
- A series of columns constructed or inserted into the ground to transfer the load of the structure to firm strata.
- 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?
1 - Sheet Piles.
- A deep trench is excavated and concrete is poured in-situ.
- The piles can be used to firm basement walls or act as retaining walls.
2 - Seacant Piles.
- Interlocking piles (male and female) 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
3 - Bored Piles
- An auger is used to excavate the soil and then concrete is poured in when complete.
4 - Pre-Cast Piles
- Piles are hammered into the ground. This is not often favored due to the noise levels associated with installation and the lack of flexibility in terms of depth required.
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What are the different ways that the piles transfer their load to the surrounding ground?
1 - End-Bearing. Transfer load through low bearing capacity soil to a firm stratum such as rock or very dense sand.
2 - Friction. Bear on frictional resistance between their outer surface and the soil in contact.
3 - Settlement Reducing Piles. Usually incorporated beneath the central part of a raft foundation in order to reduce differential settlement to an acceptable level.
4 - Tension Piles. Resist uplifting forces that might otherwise force the structure to become 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 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 is never certain and the procurement route used determines who takes the risk.
- For example, under a traditional or design and build procurement the contractor would normally take 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 foundations are useful in low bearing capacity soils.
- They can be a solid raft slab or a beam and raft such as a ground beam system and suspended PC concrete floor.
Under what conditions would you expect a raft foundation to be used for a sub-structure?
- 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 cutting a shallow continuous excavation to support the perimeter and internal walls.
- They are also referred to as strip footings and are suitable for most sub-soils and light structural design.
What are Pad foundations?
They act as an earth retaining structure for the whole or part of the 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 and are cut back to a safe angle. This eliminates the need for any temporary support work and can be used to construct basement walls. It 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 center of the basement is excavated first, then the basement slab is 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. Consists of a slab raft foundation to serve as the basement floor and distributes the building load. The basement walls serve as the retaining walls.
- Box and cellular raft. Similar to the 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. Can be used for new or refurbishmnet 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 utilizes piston driven carbide tipped heads which impact the surface material at a rapid rate.
This pulverizes 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?
- Often quick to assemble in comparison to alternative methods.
- 100% recyclable and inorganic, meaning they will not warp, split, crack or creep.
- Highest strength to weight ratio of any building material.
- Steel is not vulnerable to termites or any type of fungi or organism.
- Dimensionally stable and do not expand or contract with moisture or temperature changes.
- Consistent material quality due to strict manufacturing controls.
- Non-combustible and will not contribute to spread of a fire.
- Lighter in comparison to concrete resulting in cheaper foundation solution.
What are the technical disadvantages of steel frames?
- Require fire protection to be retrospectively installed.
- Fixing components may require replacing over time.
- Price of steel often fluctuates and can result in lack of cost certainty.
- Installation of steel frames requires experienced builders at additional cost. Resources can be difficult to acquire pending market conditions.
What are the technical advantages of concrete frames?
- Fire protection is 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 constructions.
What are the technical disadvantages of concrete frames?
- Time consuming to install in comparison to steel frames.
- 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.
- Concrete frames are often heavier and require larger foundations.
Describe a typical Cold Flat Roof Construction.
- The roof void or slab is insulated from below and it is therefore at a colder temperature than the room below during cold weather.
- Insulation is located above the 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 to the joists and finished with the respective roof covering.
Describe a typical warm 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 structure.
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.
