Steel, CLT & Concrete

Question 1

What are the advantages and disadvantages of steel vs concrete frames?

Answer 1

Tensile Strength - Steel has better tensile strength, concrete needs reinforcing with steel rebar to give it tensile strength
Space - steel can achieve longer spans, better suited for open plan office spaces than concrete, uninterrupted floor plates
Fire - Concrete can endure high temps for long time without losing structural integrity, steel needs to be fireproofed, can be expensive
Acoustics - concrete is much better
Programme - steel long lead in time, whilst fabricated etc, so need to fix design at an earlier stage but quicker on site programme, concrete minimal lead in time but longer on site process due to formwork etc
Cost - steel has risen in the recent history

Question 2

What is the price of steel per tonne currently?

Answer 2

Depending on the logistics / methodology of installation:
- Blue sky £2,500/tonne
- Tight constraints / manhandling - £3,500-£5,000/tonne

Question 3

What are the advantages of a steel frame?

Answer 3

• Quick onsite assembly
• Can be recycled and can construct using re-use (sustainable)
• Lighter than concrete frames meaning can therefore benefit from cheaper foundation solutions

Question 4

What are the disadvantages of a steel frame?

Answer 4

• Requires fire protection which can be costly
• Price of steel often fluctuates, however recently it has levelled out
• Energy intensive to produce

Question 5

What are the advantages of a concrete frame?

Answer 5

• Easily mouldable to the required form
• Inherently good fire, thermal and acoustic properties
• Cheaper than Steel and CLT alternatives

Question 6

What are the disadvantages of a concrete frame?

Answer 6

• Cannot be recycled and therefore less sustainable
• Heavier than Steel and CLT and therefore larger / more expensive foundations are required
• Needs reinforcement and therefore impacted by steel price fluctuations

Question 7

What are the advantages of CLT?

Answer 7

• Quick onsite construction due to pre-fabrication offsite
• Can be sustainably sourced
• reduced onsite labour
• lightweight therefore reduced load on the building (ibex house)

Question 8

What are the disadvantages of CLT?

Answer 8

• More expensive than steel/concrete
• Being able to insure the building may become harder

Question 9

What rates would you expect for concrete, reinforcement, formwork currently?

Answer 9

Concrete - £210/m3
Reinforcement - £1,400/T
Formwork - £60/m2

Question 10

What rates are you currently using for steel in your cost plans?

Answer 10

Columns and Beams - £4,500/T
15% allowance for connections
Intumescent Paint - £750/T

Question 11

What allowances do you have for CLT?

Answer 11

Need to make allowances for:
- Sound insulation
- CLT Slab - £185/m2
- Fire line boarding / encapsulation - 3 layers £250/m2
- Protection from elements during construction
£435/m2

Question 12

How do you fire proof CLT?

Answer 12

• Encapsulate the timber - using fire boarding to cover the exposed surface of the timber
• would always refer to the fire report