Construction Technology and Environmental Services Flashcards
Which RIBA Stage is on-site construction?
RIBA Stage 5 - Manufacturing and Construction.
What is buildability?
- Buildability can be defined as the extent to which the design of a building facilitates the ease of construction.
- To help improve buildability, early contractor involvement should be considered to benefit from their experience and expertise.
What are the benefits of off-site construction over in-situ construction?
Safety - Hazards such as falls from height are more likely to occur on site than in a factory.
Efficiency and quality - Construction takes place in a controlled environment.
Sustainability - Reduction in waste produced.
Speed - Work in the factory can be scheduled to begin at the same time as other activities on site, resulting in a shorter build programme.
What is the difference between building works and civil engineering works?
- Building works: all types of buildings such as houses, offices, shops, hotels, hospitals, etc.
- Civil engineering works: drainage schemes, highways, culverts, bridges, retaining walls, etc.
What is the substructure of a building?
- Substructure is the lower portion of the building (in the ground) which supports the superstructure.
- Transmits the loads of the building to the ground.
- Includes foundations, basements and retaining walls etc.
What is ground heave?
- Ground heave is usually associated with clay soil, which swells when wet, cause the upward movement of the ground
- As the soil generally cannot expand downwards or sideways, the result is that the exposed upper surface of the soil rises
What are some of the techniques available for ground improvement?
- Vibro compaction.
- Vibro stone columns.
- Vertical drains and vacuum consolidation.
- Soil mixing.
- Dynamic compaction.
- Dynamic replacement.
What are the different forms of excavation?
- Site clearance operations (removing vegetation and rubble).
- Stripping topsoil.
- Reduced level dig (to reach formation level).
- Cut and fill.
- Excavation for foundations.
What are the key factors the contractor should consider when excavating?
- Nature of the soil and the moisture content of the ground.
- Method of excavation.
- If ground support systems are required.
- Proximity of existing buildings.
- Depth of excavation.
- Underground services and drainage.
Can you explain some of the techniques for waterproofing a basement?
- Tanking - Materials such as asphalt, polythene sheeting, bitumen, etc. are applied internally or externally to provide a continuous membrane to the base slab and walls.
- Drained Cavity - This method accepts that a small amount of water seepage will occur. Cavity walls are formed, and the water seepage is collected in the cavity and drained or pumped away.
Have you come across the term SUDS?
- Sustainable Urban Drainage Systems.
a SUDS are designed to manage stormwater locally (as close to its source as possible), mimic natural drainage, and encourage its infiltration and/or attenuation. - SUDS help reduce the reliance on existing drainage infrastructure.
Can you detail a typical road build-up please?
- Compacted and rolled type-1 subbase (100-250 mm).
- Base course (70 - 150 mm).
- Binder course (50 - 100 mm).
- Wearing/surface course (20 - 40 mm).
What is the purpose of a foundation?
- Foundations provide support for structures, transferring their load to the ground to avoid excessive settlement.
- The foundations should bear the loads of the superstructure.
What are the typical considerations when selecting the type and size of foundations?
- The total load of the building.
- Nature and load bearing capacity of the ground.
- Type of structure.
- Cost.
- Construction constraints (for example, their proximity to adjacent buildings or structures).
What are the different types of foundation?
- Strip foundations.
- Pad foundations.
- Raft foundations.
- Piled foundations.
What is a raft foundation?
- A raft foundation is essentially a continuous slab that extends over the entire footprint of the building.
- The raft spreads the load of the building over a larger area than other foundations, reducing the stress acting on the ground below.
What are pad foundations?
- Pad foundations are typically used to support individual or multiple columns, spreading the load to the ground below.
- They are usually square or rectangular on plan and can be reinforced or non-reinforced.
What are strip foundations?
As the name suggests, the formation is a strip of linear structure that ultimately serves to spread the weight across the total area of the ground and is typically used to support masonry.
What are pile foundations?
- A pile is a column (usually concrete) that extends deep into the ground.
- Where the bearing capacity of the soil is poor or imposed loads are very heavy, pile foundations may be required.
There are two main types of pile:
- End bearing piles.
- Friction piles.
There are two main construction methods:
- Bored piles.
- Driven piles.
In what scenarios might a piled foundation be the best solution for the project?
- Where the structure is heavy and the underlying soil is weak.
- In areas where settlement issues are common.
- Where the sub-soil water table is high.
- Where the load distribution of the structure is not uniform.
- Presence of horizontal forces.
Can you explain how end bearing and friction piles transfer the load of the building?
- End bearing piles - The bottom of the pile rests on a layer of strong soil or rock, the load of the building is transferred through the pile onto the strong layer.
- Friction piles - Friction piles work on a different principle, friction piles develop most of the pile-bearing capacity by shear stresses along the sides of the pile. In other words, the surface of the pile works to transfer the forces to the soil.
What are the differences between bored piles and driven piles?
The fundamental difference lies in their point of manufacture. A driven pile is formed off site under factory-controlled conditions and a bored pile is cast on site.
What are the key advantages and disadvantages of driven piles?
Advantages:
- Piles can be precast to the required specifications.
- Piles of any size, length and shape can be made in advance.
- A pile driven into granular soil compacts the adjacent soil mass, the bearing capacity of the pile may increase as a result.
- Fast, neat and clean installation.
Disadvantages:
- Requires heavy equipment for handling and delivery.
- Increased noise and vibrations generated by driving the piles.
- It can be costly if the piles are too short.
What are the key advantages and disadvantages of bored piles?
Advantages:
- Any size or shape of pile can be formed on site.
- There is no risk of damage during delivery and handling.
- Reduced vibrations and noise.
Disadvantages:
- Significant spoils are generated that need to be handled.
- Reliance and coordination on multiple trades (reinforcement crew, piling crew and concrete supplier).
- Unlike driven piles, bored piles do not improve the bearing capacity of the ground.
What are secant pile walls?
- A wall is formed by installing interlocking piles which create a solid barrier free of gaps.
- Typically used to form a retaining wall.
What is underpinning and why might it be required?
- Underpinning is a method for repairing and strengthening existing foundations.
- Stabilising foundations undergoing settlement.
- Stabilising foundations that have moved because of landslips.
- Stabilising foundations affected by erosion, subsidence, or heave.
- Stabilising foundations affected by vibration damage.
- To increase the load capacity of the existing foundations.
- To accommodate a new adjoining building, new basement, or deep sewer.
What is the superstructure of a building?
- The structural components of a building are constructed above ground level (usually everything above the damp-proof course).
- The basic components of a building’s superstructure are columns, beams, slabs, walls, etc.
What is the envelope of a building?
- A building envelope is the boundary between the interior and exterior of a building.
- The materials and components that form the external shell of a building such as brickwork, cladding, curtain walls, etc.
What are the key considerations when designing external walls?
- Weather protection.
- Fire resistance.
- Acoustic and thermal performance.
- Structural performance.
- Appearance/aesthetics.
- Expected lifespan.
- Future maintenance.
Can you briefly explain what a retained façade is?
- The façade of the building is preserved while the rest of the structure is remodelled, or a new structure is built behind it.
- Façade retention is often used when restoring listed buildings.
What are standard brick dimensions in the UK?
Standard bricks are 215mm x 102.5mm x 65mm.
How many UK standard size bricks are required per m2?
60 bricks per m2.
How many UK standard size blocks are required per m2?
10 blocks per m2
What are weep holes?
- Small openings in the outer skin of masonry construction.
- Weep holes provide ventilation for the cavity and allow moisture to drain away.
Can you name two different types of brick bond?
- English bond - Alternating courses of headers and stretchers.
- Stretcher bond - The most common brickwork method. The vertical joints are staggered each time by half a brick.
What is a curtain wall system?
Typically, curtain wall systems comprise a lightweight aluminium frame onto which glazed or opaque infill panels can be fixed.
What are movement joints and why are they used?
- A movement joint is designed to safely absorb the expansion and contraction of construction materials.
- Movement joints can also allow for movement associated with ground settlement or seismic activity.
What are the key differences between wet rot and dry rot?
- Wet rot and dry rot are two different types of fungi.
- One of the main differences between wet rot and dry rot is that wet rot needs a higher moisture content to grow. Wet rot fungus likes to grow on timber with a high moisture content of around 50% and above
- while dry rot will germinate at a lower moisture content of around 20% to 30%.
What are the key characteristics of wet rot?
- Wet and spongy to the touch.
- Affected timbers will appear darker.
- Localised fungal growth.
- Affected timber is vulnerable to shrinkage.
- More likely to be accompanied by a damp, musty smell.
What are the key characteristics of dry rot?
- Dry and brittle appearance.
- There may be orange spore dust.
- White strands (known as hyphae).
- White or grey cloud-like structures.
- Rusty brown fruiting bodies.
