Construction Technology Flashcards
What are the approved documents? What ones are applicable to your project?
Approved documents are guidance notes issued by the government that provide performance criteria and examples/solutions for achieving compliance.
One I have reviewed recently is ‘Approved Document B’ which covers fire safety, comparing the fire safety report against the fire resistance minimum standard for an upper floor (60mins with sprinkler system).
Can you please explain how a composite CLT upper floor is constructed?
- Concrete beam in the middle, structural Z beam at side.
- CLT beam running between.
- Raised Access floor on pedestals.
- 10mm Plywood
- Tiles (oversize/cut)
- Fireboarding and stopping between column and curtain walling.
Can you please tell me what different types of retaining wall you are aware of?
Gravity retaining wall - use the gravitational force of their own weight to restrain the lateral force of the earth (can be masonry unit, poured concrete, stone). Suitable up to 3m.
Cantilever retaining wall - Cantilever walls are built using reinforced concrete, with an L-shaped, or inverted T-shaped, foundation. This kind of retaining wall consists of a stem and a base slab (or footing) which sits under the backfill. The vertical stress behind the wall is transferred onto the foundation, preventing toppling due to lateral earth pressure from the same soil mass, allowing cantilever walls to stand unobstructed. Suitable up to 5m.
Embedded retaining wall - Embedded retaining walls work by counteracting the active earth pressure being exerted on the wall above. Embedded retaining walls extend deeper than the excavation to take advantage of the passive earth pressure of the ground below. In some cases, embedded walls can extend to 40m deep. This type of retaining wall is used to form near-surface underground structures, such as basements, car parks and metro stations. (piles)
What type of external wall does the Brent Cross 3 building have? Please describe the components according to a cross section of the wall?
Summarise the energy strategy from the Brent Cross 3 building?
- Energy Source - The building is all Electrical. It has an incoming HV supply and 2No. transformers providing an estimated building load of 2.2MVA. A standby generator is provided for life safety systems. The building is all electrical, with no incoming gas. No renewable are proposed for the scheme.
- Heating and cooling is provided via district heating and cooling networks.
- The floorplates are provided with heating and cooling via the fan coil units and passive chilled beams.
What are thermal bridges? Where are they usually located and how are they treated?
Thermal bridges are weak points in the building envelope which allow heat to pass through more easily, due to materials which are better conductors of heat forming a bridge between the inner and outer face of construction.
They usually occur where elements of the building penetrate through its insulated fabric, i.e. glazing, or where the structure penetrates the building envelope, i.e. steel columns, or at junctions between two or more elements in your building envelope.
You can treat thermal bridges by getting a thermal study and rectifying the areas, i.e. replacing windows, foam spraying insulation on gaps in your roof.
How is a CFA pile built? And a bored pile?
CFA - A continuous flight auger is drilled/rotated into the ground, once at the required depth, concrete is poured through the hollow stem whilst it is slowly removed. Steel reinforcement is usually inserted to enhance structural capability.
Bored pile - Bored piles, also known as drilled shafts, involve drilling a hole into the ground using rotary drilling equipment. Once the hole is drilled, it is filled with concrete and reinforced with steel rebar.
Bored piles can be used to go to greater depth and support higher load bearing capacity.
Can you explain the build up of a flat roof?
- 12.5mm plasterboard
- Vapour control layer
- Joists
- 18mm ply deck
- 2 layers of rigid insulation
- Single ply waterproof membrane
What types of flat roof are you aware of?
Cold Roof/Deck - A cold roof system sees the insulation placed immediately above the ceiling between the joists, with ventilation space above the insulation.
Warm Roof/Deck - A warm roof system sees the insulation sitting above the deck/structural elements, enabling them to be kept close to the temperature of the inside of the building (warm roof).
Invented Warm Roof/Deck - An inverted roof puts the insulation above the roof covering. The insulation is then protected with a layer of chippings or concrete paving.
How is the level of prefabrication measured according to government guidance?
- Percentage of Prefabricated Components
- Degree of modularisation
- Time savings
- Cost efficiency
- Quality control
What are the RIBA plan of work stages?
0 - Strategic Definition
1 - Preparation & Briefing
2 - Concept Design
3 - Spatial Coordination
4 - Technical Design
5 - Construction
6 - Handover
7 - In Use
What are 5 new changes as a result of the Building Safety Act 2022?
- There’s a requirement for a ‘golden thread’ of information. The BSA mandates the creation and maintenance of a comprehensive digital record of safety information throughout a building’s life cycle.
- Requirement for HRB to register with the Building Regulator
- New Gateways introduced.
- HRB with at least 7 storeys / 18m and at least 2 resi units must now have 2 stairs/cores, in order to improve fire safety.
- New principal designer role, separate from CDM which is related to managing compliance of the design and construction works with the building regulations.
What are the BSA gateways?
The Building Safety Act, 2022 features three gateways at key stages in design for higher-risk buildings. These gateways are as follows:
Planning Gateway one – at the planning application stage
Gateway two – before building work starts
Gateway three – when building work is completed
These gateways are also known as ‘hold points’ and are required to ensure building safety. The HSE will require assurance before building work can commence, before a building can be certified complete, and before a building can be occupied.
Name 3 modern methods of construction?
Volumetric (modular) - Three-dimensional units produced in a factory, fully fitted out before being transported to site and stacked onto prepared foundations to form the dwellings.
Panellised - Flat panel units built in a factory and transported to site for assembly into a three-dimensional structure or to fit within an existing structure.
Hybrid - Volumetric units integrated with panellised systems.
What are the different types of pre-fabrication?
Panellised wood framing - Long timber frames that have been laminated and coated with plywood or roofing material make up panelised wood framing systems. They are frequently utilised for building roofs.
Sandwich Panels - Sandwich panels are made up of two layers of materials with an insulating core between them. The exterior layers may be made of concrete, plywood, or stainless steel, while the insulating layer may be made of rubber, foam, or paper.
Steel framing systems - Steel framing systems offer a fast-track metal (galvanised steel) stud panel framing system providing a carrier for insulation, exterior cladding and interior boarding. Cold-rolled galvanized steel sections are typically supplied to site as individual components which are assembled in-situ using screwed connections. Components can be supplied pre-cut to required lengths or cut as needed on site.
On the enabling works, how did you establish the existing info was inaccurate?
The trial pit holes (using vac ex) revealed that services were not in the location specified on existing drawings.
What other non-invasive excavation methods could you have used?
Air pick - Air picks are tools that use compressed air to loosen soil without damaging buried cables, pipes and roots.
Hydrovac - Using pressurized water to break up soil.
Insulated hand tools - Insulated tools to prevent operatives being electrocuted.
What are the advantages and disadvantages of using vac-ex?
Advantages:
- Non destructive so well suited for sensitive excavation where risk of live services or tree roots etc.
- Decreases risk to operator as the intake nozzle can be controlled remotely.
- It allows for precise excavation.
- It can be faster and more efficient than manual digging.
Disadvantages:
Cost: The initial investment in vacuum excavation equipment can be high, and operating costs may also be significant.
Limited Depth: Vacuum excavation may not be suitable for very deep excavations, as its effectiveness decreases with depth.
Debris Management: The process generates a slurry that needs to be properly managed and disposed of, which can add to the complexity and cost of the operation
What is vacuum excavation?
Its a non-invasive method of excavation. It works by using high pressure air to loosen the soil, which is then sucked up by the vacuum.
Who initiated the water re-routing design change on the enabling works?
The design change was initiated as a result of an EW by the contractor and resolved by the design team.
What was your role on the design change?
I was responsible for assessing the contractor’s quote for the design to provide the client with confidence that it represented fair value.
What was the ground conditions on the enabling works project?
Chalk substrata.
Rock chalk strata.
What is the current standard for underground services?
PAS 128, relates to underground utility detection, verification and location. It provides a standardised methodology to ensure accurate and reliable utility surveys, ranging from D (a desktop utility record search) to A (verification by physical identification).
How was the vac-ex the fastest method?
Because scans and slit trenches (using vac-ex) would be required for the other methods, so less stops and starts to the excavation process.
What are the different services and their colours?
In the UK, underground services are marked with specific colors to indicate the type of utility. Here are the standard color codes:
Red: Electric power lines, conduit, and cables.
Orange: Telecommunication, alarm, or signal lines.
Yellow: Gas, oil, steam, petroleum, or other flammable materials.
Green: Sewage and drain lines.
Blue: Drinking water.
Purple: Reclaimed water, irrigation, and slurry lines.
Pink: Temporary survey markings, unknown/unidentified facilities.
White: Proposed excavation limits or route
How was the vac-ex approach deemed the safest?
As it as a non-invasive excavation method, and can be controlled remotely.
What was the rate of vac-ex on the project?
£2000 per day.
What was the output of the vac-ex?
7m3 per day.
What are slit trenches?
Slit trenches are long, narrow trenches usually employed to locate and confirm the position of underground services.
What was the cost difference between the 3 options?
Full vac ex option - £1,266,608.57
Perimeter slit trenching - £1,072,194.70
Slit trenching with GPR scans - £1,308,021.63
What is a walk on ceiling?
A walk-on ceiling is a specialized type of ceiling designed to support the weight of individuals walking on it.
What is a composite metal deck?
A composite metal deck is a type of structural decking used in construction to create floors and roofs. It combines a metal deck with a concrete slab to form a single, strong unit.
What is a capital cost?
The initial purchase cost.
Why was it 8 weeks quicker?
It was 8 weeks quicker as the metal deck could support operatives weight as well as the high-level M&E equipment (HEPA filter). Meaning they could install from the deck rather than having to be on the ground floor with a MEWP, thus stopping the ground floor M&E installation progressing.
What were the main items included in your impact report on your government project?
Introduction
Time
Cost
Quality
Risk
Conclusion
What are the challenges of constructing on chalk substrata?
- Highly porous, can absorb lots of water.
- If highly weathered, can behave more like soil than rock. Less weathered has stronger compressive strength.
- Chalk is susceptible to dissolution from slightly acidic groundwater leading to things like sinkholes.
What is a district heating?
District heating is a system that uses a singular central heat source to distribute hot water through a network of insulated pipes to multiple individual dwellings. It is commonly used to fulfill heating and hot water requirements in apartment complexes and provides low-carbon energy efficiently.
Heat is produced from a variety of potential energy sources including fossil fuels, biomass, geothermal or waste heat. At the building, the heat is transferred via heat exchangers into the internal heating and hot water systems.
What are the advantages of district heating?
What is a cooling network?
District cooling provides chilled water for indoor cooling purposes to multiple dwellings, similar to how a district heating system works.
