Design Economics & Cost Planning

Question 1

Can you tell me some of key factors which impact the cost of a building?

Answer 1

Location
Size 
Shape
Height
Specification
Grouping of buildings

Question 2

How does size impact the cost of a building?

Answer 2

A bigger building will have economies of scale, reducing the price subject to the size being designed efficiently

Question 3

How does the height of a building affect the cost?

Answer 3

A tall building may require more lift cores, reducing net space on each floor plate.

Bigger foundations, beams etc required

Requirements for better facades to deal with greater wind loads and sprinkler requirements for buildings over 30m high (approved doc B)

Question 4

How does the shape of a building affect the cost?

Answer 4

Curved shapes are expensive to manufacture + construct due to complexity

Inefficient shape could cause high wall to floor ratio

Most efficient shape is a square (excl circle because of curve)

Question 5

How does the grouping of buildings affect the cost?

Answer 5

Less facade per m2

Ability to share plant etc

Question 6

What might be risks associated with using BCIS?

Answer 6

Can’t interrogate rates as they are secondary

Sometimes BCIS publish data that is ‘provisional’ and not finalised yet

Question 7

What might be a problem with market testing?

Answer 7

Suppliers may provide lower costs to ‘get in the door’ or win jobs

Question 8

What are some of the key design metrics?

Answer 8

Wall to Floor
Floorplates
Net to Gross
Floor to Ceiling Heights
Shape of the building

Question 9

What is BCIS used for?

Answer 9

You can use BCIS for a source of cost data.

Data can also be manipulated or adjusted to reflect location or dates.

Question 10

What are the RIBA work stages

Answer 10

0 – Strategic Definition
1 – Preparation & Briefing
2 – Concept Design
3 – Spatial Coordination
4 – Technical Design
5 – Manufacturing and Construction
6 – Handover
7 – Use

Question 11

What are the full names for NRM1 and NRM2?

Answer 11

New Rules of Measurement 1: Order of cost estimating and cost planning for capital building works

New Rules of Measurement 2: Detailed measurement for building works

Question 12

How is NRM1 structured?

Answer 12

1 - Context & definitions

2 - Rules for preparing OCE, how to quantify non-measurable works

3 - Rules for cost planning, how to quantify non-measurable works

4 - Tabulated rules of measurement

Appendices

Question 13

What is an order of cost estimate?

Answer 13

• The determination of possible cost of a building(s) early in design stage in relation to the employer’s fundamental requirements.
• Prior to preparation of a full set of working drawings

Question 14

What is an elemental cost plan?

Answer 14

• the critical breakdown of the cost limit for the building(s) into cost targets for each element of the building(s)

Question 15

What are the 3 main ways to measure building works in a cost estimate?

Answer 15

Floor Area Method
Functional Unit Method
Elemental Method

Question 16

What information would you expect from the Client before preparing an Order of Cost Estimate?

Answer 16

 Location and availability of site.
 Statement of building use and size.
 Any refurbishment requirements.
 Initial project/design brief.
 Draft programme.
 Site conditions.
 Budget/cash flow constraints.
 Construction procurement options.
 Life span of the proposed building.

Question 17

What information would you expect from the Architect before preparing an Order of Cost Estimate?

Answer 17

 Design study sketches or drawings.
 Schedules of areas.
 Legislative constraints.
 Initial risk register.

Question 18

What estimates and costs plans are listed in NRM1?

Answer 18

• Order of Cost Estimate
• Formal Cost Plan 1
• Formal Cost Plan 2
• Pre-Tender Estimate
• Bills of Quantities
• Post Tender Estimates

Question 19

What are the key elements of on order of cost estimate?

Answer 19

Facilitating Works
Building Works 
Contractor Prelims 
Contractor OHP
Construction Cost Fees
Other development / project costs
Risk Allowance 
Inflation

Question 20

How is a Cost Plan structured?

Answer 20

• Executive Summary
• Cost Summary
• Schedule of Areas
• Unit Mix
• Pricing Notes, Assumptions and Exclusions
• Cost Reconciliation
• Benchmarking
• Detailed Cost Build Up
• Basis of the Cost Estimate

Question 21

Which would you expect to have a lower wall to floor ratio and why between an office building and a residential building?

Answer 21

You would expect an office building to have a lower wall to floor ratio as they generally have less articulation within the external wall compared to residential buildings.

Question 22

What is Value Engineering?

Answer 22

The systematic approach to enhance value by eliminating unnecessary cost while maintaining function.

Question 23

What RIBA Stages would you do a cost estimate at?

Answer 23

Typically, you would have a cost estimate in the early stages of the project. This would be at Stage 0-
2 where there are less drawings and information.

Question 24

What RIBA Stages would you do a cost plan at?

Answer 24

I would do a cost plan at RIBA Stage 3 and RIBA Stage 4.

Question 25

What are the NRM Risk Categories?

Answer 25

Design development risks
Construction risks
Employer change risks
Employer other risks

Question 26

You mention you advised on a change of wall finishes to circulation areas on Devonshire row bar fit out – what was the cost saving?

Answer 26

Circa £90k

the saving was circa £500/m2!!!

Painted plaster - £40/m2

Glazed brick including metal frame backing boards - £540/m2

Question 27

You mention specified light fittings for the Cat A project, how did this £/sqft benchmark to demonstrate it was not inline with other comparative projects?

Answer 27

Budget was £235/each
Budget was £35/m2

Architect had specified £700+ / each
Architect £80/m2

Question 28

On East Croydon you mention wall to floor ratios, what was this?

Answer 28

0.55 to 0.65

by using bolt on balconies this ratio could be closer to 0.4

Question 29

What would you expect as a good wall to floor ratio on a residential scheme?

Answer 29

0.4

Question 30

What would you expect to have a better w:f ratio – resi or office?

Answer 30

Office as usually less articulation and simple shape building but

Question 31

What are other design efficiencies you are aware of?

Answer 31

Wall to Floor 
Net to Gross
Nr of Cores 
Solid to Glazing 
Nr of lifts per unit (resi)