Estimation

Question 1

What are the 6 estimating methods?

Answer 1

1. Single rate: Functional unit of accommodation.
2. Single rate: Floor area.
3. Multiple rate: Elemental cost per (GFA) m2
4. Multiple rate: Elemental unit rate
5. Multiple rate: Approximate quantities
6. Multiple rate: BQ

Question 2

How do you estimate using the functional unit of accommodation? 2 points

Answer 2

Nr of units x Cost range = Cost
Adjust rate for finishes, location etc.

Question 3

How do you reverse budget using the functional unit of accommodation?

Answer 3

Budget / Cost per unit = Nr of units

Question 4

How do you estimate using the floor area method?

Answer 4

GIFA x Cost range = Cost

GIFA - measured at each floor level

Question 5

What are the advantages and disadvantages of using the floor area method of estimating? 9 points

Answer 5

Advantages
1. Quick.
2. Simple.
3. Ideal for early budgeting purposes.
4. Directly relates to accommodation.
5. Allows for comparisons of different designs.
6. Allow comparisons between buildings that differ in size and shape.

Disadvantages
7. Doesn’t allow for extra ceiling height eg. warehouses. Allowances must be made.
8. Very loose estimation because quantity of key elements do not necessarily increase or decrease per m2 eg. number of walls and doors.
9. Specification adjustments not feasible as quality differentials are element specific.

Question 6

How do you estimate using the elemental cost per (GFA) m2?

Answer 6

Calculate the proportion of the total cost for each element on a similar building then apply to measure for the new building.

Question 7

How do you estimate using the elemental unit rate?

Answer 7

Approximate quantity of each element x Unit rate = Cost of each element

Question 8

Name 6 sources of cost data.

Answer 8

1. Own historical data - preferred.
2. National historical data.
3. Price books.
4. Specialist subcontractor quotes.
5. Magazines.
6. Web sites eg. larger cost consultants.

Question 9

Priorities when selecting cost data? 3 points

Answer 9

1. Similar buildings.
2. Recently tendered buildings.
3. Using several comparable sources.

Question 10

What adjustments to source rates must be made? 3 points

Answer 10

1. Inflation.
2. Location.
3. Quality.

Question 11

What assumptions and exclusions should be included in cost estimates? 9 points

Answer 11

EXCLUSIONS
1. External works / preliminaries.
2. VAT
3. Professional fees.
4. Fittings and furnishings.
5. Land cost.
6. Interest charges.

ASSUMPTIONS
7. Overheads and profit added at 5%
8. Preliminaries added at 10%
9. Contingencies added at 5%

Question 12

What affects the degree of accuracy of an estimate? 3 points

Answer 12

1. Quality of information supplied / available.
2. Quality of sources of cost data.
3. Skill of the surveyor.

Question 13

What are the three adjustment calculations?

Answer 13

Time adjustment = Proposed index / Historical index

Location adjustment = Proposed index / Historical index

Cost x Time x Location = New total

Question 14

How much contingency should you allow for in an estimation? 2 points

Answer 14

5% on new builds and 10% on refurbishment.

Question 15

How do you estimate using the approximate quantities method?

Answer 15

Measurements concentrated to a few items as needed, per element. eg cavity wall - same area for external brick facing, cavity, insulation, internal block skin.