L1 - Design Economics Flashcards
What is design economics?
Design economics is the assessment of the efficiency of a building
What are different types of efficiency ratios?
Net:Gross
Wall:Floor
Solid:Glazed
GEA:GIA
Site density
£/WC - £/sqft of WCs
£/Reception
What is Net:Gross?
Net to gross is the ratio of useable space, to gross internal area of a building.
What is a common Net:Gross?
Commercial - 75/85%
Residential - 70/80%
What affects the N:G ratio?
Size of core
Size of circulation
Layouts
What is Wall:Floor?
The wall to floor ratio is the amount of facade area needed to accommodate the building’s geometry and structure.
What is a common Wall:Floor?
Commercial - 0.4/0.45
Residential - 0.5/0.6
What affects the W:F ratio?
Number of articulations
Elevation heights
Slab thickness
What sources of cost data are there and can you rank them?
- Recently tendered rates
- Internal benchmarking
- BCIS
- Spons
What is the danger with benchmarking?
Data might not be correctly inputted
Data may be outdated e.g. specification no longer being produced, can’t just TPI it
Not adjusted correctly
What is market testing?
Market testing is obtaining prices from the market.
What is the process of market testing?
Produced a mini-BoQ utilising design team drawings and specifications
Source contact details from recommended suppliers / in house recommendations
Issue mini-BoQ for suppliers to return their rates
What are drawbacks with market testing?
Price is reflective of time obtained not when tendering
Lack of competition
Supplier may not maintain price
What is inflation?
Inflation is the increase in the average level of prices and costs.
What is TPI?
TPI is tender price index
This is an allowance for fluctuations during the period from the base date to tender return.
What is the current TPI?
Q1 2025 - up 2.75%
Q1 2026 - forecast from Q1 2025, up 3.55%
What is the base date?
Date of tender return / priced offer
What is CPI?
CPI is construction price inflation
This is an allowance for fluctuations during the period of tender return to the mid-point of the construction period.
What is the current office market like?
Office refurb market has dropped off, new builds have increased 50% in last 12 months (Q4 2024)
Active demand for Grade A space
Investment remains challenged, yields have peaked
Overseas equity drives market on hotels, leisure and life sciences
What is benchmarking?
Comparison of similar schemes and key project information. This can be displayed using efficiency ratios or £/ft2.
What is the build up to a rate?
Materials, installation, labour, plant, equipment, prelims and OH&P
What is value engineering?
Value engineering is the approach which enhances value by eliminating design inefficiencies and costs whilst maintaining function
What is value management?
Value management is the identification of what Value is to the Client and enhancing it.
How do you conduct a VE workshop?
Gather information
Brainstorm
Evaluate
Develop
Present
Making the design more efficient without reducing essential performance.
