Construction Technology

Question 1

What are the various house types you’ve built?

Answer 1

Detached, semi-detached, terraced, blocks of flats (3 storeys high) (really meant standard house types with house builders)

Question 2

Have you ever dealt with any kind of brickwork defects?

Answer 2

▪ Efflorescence
▪ Mortar deterioration
▪ Cracking (compromise structure of building)
▪ Wall ties corrosion
▪ Damp penetration
▪ Damage by the brick cleaners

Question 3

What bonds of brickwork have you come across and which is the most popular?

Answer 3

Types of bonds - Stretcher, Header, English, Flemish, English Garden

Question 4

What is the purpose of a foundation?

Answer 4

Provide support for structure, transferring their load to the ground. They should bear the load of the superstructure.

Question 5

You’ve mentioned you have experience of various types of foundations. Can you give me some examples?

Answer 5

▪ Strip foundations - strip of linear structure that spreads the weight across the total areas of the ground. Typically used to support masonry. (Used in housebuilding)
▪ Raft foundation - a continuous slab that extends across the entire building footprint. This is over a larger area to reduce stress on the ground. Typically used when ground conditions are poor.
▪ Pad foundation - usually square or rectangular structures that are used to support columns. Spreads the loads to the ground. Can be reinforced (as Portland Park)
▪ Pile foundations - columns that extend deep into the ground. Use where bearing capacity of the soil is poor or imposed loads are very heavy. (Distribution of structure isn’t uniform / subsoil water table is high))

Question 6

What are the 2 types of piles?

Answer 6

1. End bearing piles (reply on the resistance f the soil or the rock at the tip of the pile to support the load)
2. Friction piles (transfer load by friction between the surrounding soil and the surface of the pile over its full length - like when you step in the mud!)

Question 7

What are the 2 main construction methods of installing piles?

Answer 7

1. Bored piles (manufactured / cast on site)
2. Driven piles (formed off site under factory-controlled conditions)

Question 8

What is underpinning?

Answer 8

Process of strengthening the foundation of an existing structure / Method for repairing and strengthening foundations.

Question 9

Briefly explain the construction of a swimming pool?

Answer 9

▪ After surveying & marking the area, area is excavated and soil taken off-site
▪ Steel formwork was used to form shape of pool and rebar placed at base
▪ Concrete was poured and cured. Concrete contain Xypex which is a waterproofing solution. At this point we filled the pool with water (with help from the local fire brigade) to test for cracking.
▪ Installation of pipes and wiring for MEP works (filers, pumps, drainage, lights)
▪ Pool was emptied then tiled using a waterproof grout
▪ Installation of MEP
▪ Complete areas around the pool (floor tiles)
▪ Fill. Test systems and chemical balancing
▪ Inspection & handover

Question 10

What are SUDS?

Answer 10

Sustainable Urban Drainage Systems - designed to efficiently manage the drainage of surface water. Alternative or in addition to typical drainage (pipework)

Question 11

What are some of the advantage & disadvantages of using a steel frame?

Answer 11

Advantages
* Faster to erect than concrete (prefab)
* High Tensile strength therefore can span long distances (good for a swimming pool)
* High strength to weight ratio
* Strong
* Durable - resistant to decay, pests and weather
* Recyclable

Disadvantages
* Lower load-bearing capacity than concrete
* Cost - Price of steel is volatile
* Different acoustic and thermal properties to concrete
* May need Fire Protection
* Lack of flexibility on site
* Needs support
* Poor thermal conductivity
* Corrosion

Question 12

What are the components needed to measure steelwork?

Answer 12

1. Structure steel frame including all components - columns, beams, braces, struts (in Tonnes)
2. Connections / Fittings and fixings (e.g. holding down bolts) - in Tonnes. Usually 10%
3. Fire protection £200/t

Question 13

What are some of the advantage & disadvantages of using a concrete frame?

Answer 13

Advantages
* Fire protection is naturally part of the structure
* Easy to fix to (cladding, other finishes)
* Good sound and heat insulation
* High compressive strength - suitable for multi-storey buildings, bridges, handling heavy loads
* Durable
* Flexible on site (poured in situ)

Disadvantages
* Low tensile strength so needs reinforcement to span
* Requires formwork (poured on site)
* Slower to construct on site
* Long curing times (max strength 28 days) - steel is immediate
* Additional items maybe costly (design change)
* Environmental impact - high carbon emission during cement production and transportation
* Weight - heaviest therefore increased foundation costs
* Maintenance if cracks

Question 14

What are the components you would need to measure for a concrete frame?

Answer 14

• Formwork
• Concrete (columns, beams, walls, floor slabs - nr, size, reinforcement, formwork finish)
• Designed joints?
• Reinforcement (would measure using a bar bending schedule)
• Tanking

Question 15

What is formwork?

Answer 15

The structure (usually temporary) used to pour concrete and mould into required dimensions. Usually stripped away once concrete has hardened.

Question 16

What are some of the advantage & disadvantages of using a timber frame?

Answer 16

Advantages
* Quick to erect on site
* Relatively lightweight - easy to transport & handle (reduce costs)
* Sustainable (if from a responsible supplier) - timber is a renewable source with lower carbon footprint
* Aesthetically pleasing (if exposed)
* Thermal performance

Disadvantages
* Requires specialist (joiners) achieve good quality finish
* Potential for wet rot, dry rot, woodworm without treatment/protection
* Need additional fire protection - more combustible that steel or concrete
* Not suitable for long spans / very heavy loads

Question 17

What are retaining walls?

Answer 17

Holds back (or retains) the soil behind it. Typical purpose is resist the lateral pressure of soil where there is a change in ground elevation.

Question 18

Can you give me some types of retaining wall please?

Answer 18

• Gravity - relies on its own weight to resist the pressure. Made using stone, concrete or masonry. Shorter walls or space for a wide base available.
• Cantilevered - made from reinforced concrete or masonry. Thinner stem, uses leverage via a base slab. Taller walls, less materials than gravity.
• Gabion - basket structure (wire mesh boxes), can be used as a more aesthetically pleasing alternative. Basket is then filled with tightly packed rocks. Flexible, permeable, and eco-friendly, often used in landscaping and erosion control
• Crib Retaining Wall - built form interlocking concrete or timber frames filled with soil or gravel. Lightweight and allows water drainage, idea for slopes and landscaping (Benwell - health & Safety issue)
• Sheet piling - temporary measure where sheet piles are driven into the ground. Steel or timber planks driven into the ground. Good for tight spaces or soft soils. Also used in temp works or waterfront applications (Rowlands Gill)