Design Economics & Cost Planning

Question 1

In simple layman’s terms explain what you mean by the term “wall/floor ratio”.

Answer 1

Wall/floor ratio is a design economics concept to maximise efficiency and minimise costs. A low wall/floor ratio means less external surface to insulate from the elements. Low ratio is cheaper to build as they require less materials for the external walls. A low ratio maximises space whilst keeping building and maintenance costs down.

Question 2

What is the most efficient building shape for wall to floor ratio?

Answer 2

A circle would be the most efficient use of walls to maximise floor area.

However, this would lead to increased costs as curved walls/windows/furniture would be more expense and it may also be difficult to maximise the functionality of the space available.

Therefore I would recommend a square shape as the best value floor plan to maximise wall to floor ratio.

Question 3

Name some design economics contributors?

Answer 3

Building height (wall to roof ratio/structure/foundations), building shape, orientation/energy efficiency, wall/floor ratio,

Question 4

How does cost planning affect design development to keep control on project costs?

Answer 4

Cost plans provide an indication of the project cost.

This provides guidance on whether the proposed scheme is above or below the budget and whether the client needs to reduce the design scope, increase the budget or increase design scope if they are not spending the full budget.

Question 5

How would you carry out a preliminary estimate? Say a stage 1 cost plan?

Answer 5

I would take the areas of the building and apply high level rates to these areas.

These rates would be taken from historic benchmarks projects within my company or maybe rates from the BCIS

Question 6

What level of detail would you give for a preliminary estimate, say for example you’ve been given a schedule of accommodation, how would you formulate costs from there?

Answer 6

The level of detail provided to me would be basic so I would match this with a high level costing, applying rates to areas in the schedule of accommodation.

Rates would be from in house company data or BCIS.

Question 7

Brickwork to window ratio?
Benefits for both sides?

Answer 7

Often called the Window-to-Wall Ratio (WWR), is the proportion of wall area that is covered by windows. Generally, a lower WWR is considered better for energy efficiency, while a higher WWR can lead to increased natural light and views.

Question 8

What other costs would you include below the line of your base construction cost?

Answer 8

Professional fees
surveys
contingencies
client direct costs
insurances
planning fees
inflation
VAT

Question 9

What would you exclude from a cost plan?

Answer 9

You may exclude:
- VAT,
- inflation,
- land acquisition costs,
- Section 106 Community infrastructure,
- loose furniture
- Rights of light
- Party wall
- asbestos/contaminated ground

Question 10

What kind of costs would you include in a life cycle costing?

Answer 10

CROME

Construction
Renewal
Operation
Maintenance
End of life

Question 11

What kind of maintenance costs would you include in a life cycle costing?

Answer 11

Redecoration
Inspections
periodic maintenance
repair

Question 12

Would you look to discount any costs included in a life cycle costing?

Answer 12

Discount costs in a life cycle costing refer to the process of adjusting future expenses to reflect their present value.

Question 13

Highgate West - Describe one element / example that was value engineered, what was your role and what was the outcome.

Answer 13

As the project was a hospital project, Altro Whiterock wall cladding was specified as a hygienic wall cladding to a number of the rooms.

I suggested that the extent of the Whiterock specified was excessive and beyond the ER’s and that it could be reduced in some rooms and replaced with a simple paint finish. The suggestion was accepted and the architect reviewed areas where the Whiterock was not essential.

Question 14

Highgate West - Provide an example of how the design was amended following your cost plan?

Answer 14

The quantity of Whiterock hygienic wall cladding was reduced.
Refurb work to some non-essential rooms were removed from the scope.

Question 15

What information is included in the NRM1 document?

Answer 15

• Measurement rules for order of cost estimating
• Measurement rules of cost planning
• Tabulated rules of measurement for elemental cost planning

Question 16

When would you use NRM 1?

Answer 16

Order of cost estimating and cost planning for capital building works

Question 17

When would you use NRM 2?

Answer 17

Detailed measurement for building works

Question 18

When would you use NRM 3?

Answer 18

Order of cost estimating and cost planning for building maintenance works

Question 19

What are the pitfalls with using BCIS cost information?

Answer 19

• relies heavily on accuracy of information entered
• Not always easy to understand what works are included and where
• Specialist installations may skew costs
• could be outdated
• economic or political pressures on the benchmark project may not be known
• project difficulties not known
• adjusting for inflation is only an approximate estimate, inflation is not a fixed rate across all materials and trades

Question 20

What are the pitfalls with using in house benchmarking data?

Answer 20

adjusting for inflation is only an approximate estimate, inflation is not a fixed rate across all materials and trades

economic or political pressures on the benchmark project may have changed

Over reliance on historical data could lead to inaccurate predications about the future

Question 21

Elleray Hall - Advise me what market factors had caused the cost rises between cost plans. How did you establish / find out this information?

Answer 21

At the time, the main market factor leading to cost increases was the Ukraine conflict. I established this information through reading articles on the matter as well as witnessing price increases on other projects within our company.

Question 22

Elleray Hall - Describe how you carried out the cost exercise for the partition. What information did you need to carry out this task?

Answer 22

I extracted the costs from the cost plan for existing specification. I then reviewed the works that would be required for replacing the glazed partition with a fixed partition and costed those, using quantities taken from the original costs and rates used elsewhere in the cost plan.

Question 23

Elleray Hall - What was the saving for removing the glazed and movable partitions?

Answer 23

£25k-£30k

Question 24

Elleray Hall - What was the saving for changing the glazed partition to a studwork partition?

Answer 24

Approx. £15,000

Question 25

Elleray Hall - Can you name a VE suggestion other than the partitions or those included in your case study?

Answer 25

It was suggested that the building be built with a higher ground floor level than designed as the site was being dug out to achieve the existing level. However, there was a planning height restriction so this option was not adopted.

Question 26

Arkwright Terraces - How did you adjust costs for location factors?

Answer 26

In the Arkwright cost plan, when using benchmarking I used BCIS to find out the location factor of the original benchmarking and then the location factor of the Arkwright works. I then divided the Arkwright factor by the benchmark factor and used the resulting ratio to adjust the benchmark costs.

Question 27

Arkwright Terraces - What were the potential cost risks at Stage 2?

Answer 27

Design development risk Also included pots in the cost plan for construction risk employer change risk employer other risk

Question 28

Arkwright Terraces - Which BCIS indices did you use to calculate inflation and how?

Answer 28

I used Tender Price Index from cost plan issue date up to expected start on site. I then used the General Building Cost Index to uplift the cost from start on site to expected mid point of construction, to get the average increase across the construction period.

Question 29

What are the risk pots included in NRM1?

Answer 29

Design development risk Construction risk Employer change risk Employer other risk

Question 30

What would be typical contingency levels at each of the pre construction RIBA stages? What would be the approximate split into NRM1 Risk pots?

Answer 30

Stage 1 (Preparation and Brief) 15–20% Stage 2 (Concept Design) 10–15% Stage 3 (Spatial Coordination / Developed Design) 7.5–10% Stage 4 (Technical Design) 5–7.5% These would consist of Design development at 33% Construction risk 33% Employer Change risk 22% Employer other risk 11%

Question 31

Arkwright Terraces - How did you produce the risk allowance figure?

Answer 31

Risk register workshops

Question 32

What are the differences between Employers Change Risk, Construction Risk, Design Development Risk & Employers Other Risk?

Answer 32

Design development risk - used during design process for risks associated with design changes Construction risk - for use during the construction process to provide for the risks associated with site conditions, ground conditions, existing services and delays by statutory undertakers. Employer change risk - use during both the design process and the construction process to provide for the risks of client driven changes Employer other risk - early handover, postponement, acceleration, availability of funds, liquidated damages

Question 33

Why did you include a list of assumptions and exclusions in the cost plan?

Answer 33

To ensure there was no doubt about the items included in the cost plan and the way that they were costed. This reduces any potential misunderstandings and disagreements later in the project.

Question 34

Give me some examples of cost plan exclusions?

Answer 34

VAT Party wall awards Rights of light inflation Community Infrastructure Levy Section 106 Asbestos and contaminated soil land purchase

Question 35

Give me some examples of cost plan inclusions/assumptions?

Answer 35

Inclusions: construction costs prelim costs contingency Assumptions: procurement route Materials used Reinforcement quantities

Question 36

Arkwright Terraces - What VE suggestions did you make?

Answer 36

Change the finishes, including floor tiling scope and reducing the quantity of wall tiles in the bathrooms. Replace timber windows with aluminium or uPVC windows

Question 37

Give me an example and details of a cost plan that you undertook?

Answer 37

Harlow Museum Exhibition Extension Using drawings on Cost X OR I undertook the Arkwright cost plan which was for 8 nr two storey terraced houses There were two options, one with traditional build and one with modular build.

Question 38

Arkwright Terraces - Was the traditional or modular build more expensive?

Answer 38

It was only 8 houses so the saving that might be made from a significant number of houses was not realised and the modular build was more expensive.

Question 39

At Elleray community hall, you mention the removal of the glazed portion of the stud wall. What did you consider might have been the reason for the inclusion of this glazed section, and was cost the only objective for this alteration?

Answer 39

The glazed section was there to make the hall seem open and not closed off when the movable partition was open. Another benefit would be that the stud partition won't need cleaning as often as the glazed partition would have.

Question 40

At Arkwright Terraces, which assumptions and exclusions did you make to the cost plan document?

Answer 40

Assumptions were things like strip foundation depth, ground beam reinforcement amount, Exclusions were: VAT asbestos, contaminated ground land purchase costs

Question 41

What would a typical strip foundation depth be?

Answer 41

600mm depth, minimum 450mm to avoid frost action

Question 42

What would typical reinforcement amount be for the ground beams foundation.

Answer 42

I would speak to structural engineers to find out this information. Or look at my guidance table. 200kg/m3

Question 43

at Arkwright terraces, you produced a cost plan to advise the client on the cost of the proposed scheme as well as the time quality and buildability. So just in a nutshell, what was this advice

Answer 43

The advise was that the modular construction would be more expensive but not significantly more and that works would be quicker on site and easier quality check due to offsite manufacturing.

Question 44

What sort of information could you expect at RIBA stage 2?

Answer 44

A concept design that shows layout and room types Outline strategy for structure, services and sustainability

Question 45

Highgate West - Could you tell me some of the value engineering options implemented?

Answer 45

Whiterock reduction Removal of some rooms which did not require essential refurbishment.

Question 46

Highgate West - How did you ensure quality was not compromised during the VE process?

Answer 46

The Value Engineering process revolved around improving value for money for the employer by either reducing costs whilst ensuring the ER's were still achieved, or increasing the value of items for the same cost.

Question 47

Elleray Hall - You talk about market factors affecting costs. What market factors were at play and how did they impact costs?

Answer 47

The industry was still suffering from increased costs due to the Ukraine conflict.

Question 48

Elleray Hall - Could you tell me the cost per m2 for glazed partitions?

Answer 48

I would refer to a price book, historic data or BCIS for a rate. If I had to make an assumption without looking then I would say £1,000-£1,200.

Question 49

Arkwright - What risks did you include within the cost plan?

Answer 49

It was a stage 2 cost plan, the risks pots were design development construction employer change employer other (Things like funding, early handover, acceleration, postponement)

Question 50

Did you engage in any third party advice or second opinions at the Elleray Community Hall project with regards to additional scopes of work, or how did you ensure that the additional works were as you term "good value for money"?

Answer 50

I reviewed contractor's variation costs against costs that we had as a company, price books and potentially quotes from other companies.