Estimating & Tendering
Estimating work involves dealing with
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Measurements and quantities
Pricing and rates
Subcontract packages
Tender preparation
Types of contract
-Lump Sum or Hard Money contracts
-Cost plus %-age contracts
-Cost plus fixed fee contracts
TERMINOLOGY
Provisional Cost sum, is a cost to supply and fix an item
Prime cost item, is the price for supply only
Example 1
A $10 000 PC sum was allowed for A/C in the contract. The
actual cost ended up being $8 500, so the client gets a $1 500
refund.
Example 2
A $10 000 PC sum was allowed in the contract. Actual cost was
$11 500. Charge the client the extra $1 500 plus your margin
of say 10-%, a total of $1 650.
Example 3
$35/m2 for a 100 m2 tiled floor was allowed in the contract. If
the tiles the client chose cost $30/m2, the client gets a refund
of $5/m2 x 100 m2 = $500.
More Terminology
Client Contingencies: This is an amount set into the contract to
cover an unknown amount of work. Say you allow $10 000 for
excavating through rock. At the completion of the contract
the contractor must accurately account for the actual costs
and offset it against the allowance made.
Contractor Contingencies: Contractors can use contingency
allowance for unknown events that they are contractually
bound for. In this instance it covers the contractors risk and
can be a %-age on the contract value and dependant on how
risky you think the job is. If the contingency is not used, it is
not returned to the client but increases the contractor’s
profit.
Factors to consider when tendering
- How much work have you already got on? Do you want or
need more work?
- Can you handle more work and is it going to be profitable?
- Are you technically and financially capable?
- Who is the client or Architect? Good to work with?
- How many tenderers are there likely to be?
- Who is the main competition? Are they desperate for work?
- What are your chances of success?
EARTHWORKS
Demolition?
Clearing and levelling the site
Setting out new buildings
Excavating for footings
Minor demolition example
Estimate:
Machine hire: 20 hrs @ $60/hr = $1 200
Labour: 1 person 20 hrs @ $25/hr = $500
Truck hire: 15 hrs @ $50/hr =
$750
Dumping fees: 85 ton @ $8/ton = $680
Total = $3 130
Terminology
A Foundation is the prepared soil that you are going to start
building on
A Footing is usually made from reinforced concrete and is the
first thing you build upon that foundation
ESTIMATING SHEET
Project:
Estimator:
Location:
Extended
Date:
Sheet No.
Description
Unit
Form 1/A
of
Quantity
Rate
Estimate
Example – raft slab footing
5 x 5 m in plan with 500 x 300 mm beams around the perimeter
and a 100 mm thick slab. Edge rebate for brickwork.
86
100
120
150
500
300
150
TRENCHING incl edge form
Description
Unit
Setting out: 1 person ½ day
hr
Backhoe 1 day
hr
Clear site to 150 mm
m2
Labour: 2 persons 1 day
hr
Spoil removal 6.8 m3
ton
Total to summary
Qty
4
8
25
16
11
Rate
30
55
25
30
11
$
120
440
625
480
121
$1 786
CONCRETE placement and finishing
Description
Unit Qty
Labour 2 persons 1 day
hr
16
Concrete pump*
No.
1
Vibrator (own)
No.
1
Miscellaneous
Total to summary
• Due to limited site access
Concrete supply
m3
6
Rate $
30 480
350 350
100
$930
120 $720
Quantity of concrete (Use centre lines to measure)
5000 mm
5000 – 2 x 60 = 4 880
5000 – 2 x 150 = 4 700
5000 – 2 x 300 = 4 400
5000 – 2 x 350 = 4 300
86
100
120
150
500
300
150
Slab:
4.4 x 4.4 x 0.1 =
1.94 m3
Beam: 0.3 x 0.5 x 4.7 x 4 =
2.82 m3
Wedge: 0.15 x 0.15 x 0.5 x 4.3 x 4 = 0.19 m3
Rebate: -0.12 x 0.086 x 4.88 x 4 = -0.20 m3
4.75 m3
Add 20% 0.95 m3
5.7 m3
Say 6 m3
REINFORCING
Description
Unit Qty
Reo bars 6 Y16
20 lm x 6 + 20% lap/waste
lm
144
Ligatures pre-fab W10
@ 0.6 m cts. 20/0.6 + 20%
No. 40
Fabric F72 to slab
5 x 5 = 25m2 + 20% laps
m2
31
Chairs and ties
item
1
DPM 100 x 2 m roll
No.
1
Total to summary
Labour 2 persons 1 day
hr
16
Rate
$
2.80 403
2.50 100
5.50 171
50
50
86 86
$810
30
$480
SUMMARY
Labour
Trenching
$1 786
Reo
$480
Concrete
$930
Material
Reo
$810
Concrete
$720
Total $4 726
Example – Carpentry
Say we have a four walled room 5 x 5 m with 2.7 m high walls.
All timber is 70 x 35 pine with studs at 600 mm c/c.
Description
Unit Qty
70x35 top and bottom plates
lm
41
70x35 studs 38@2.7
lm 103
70x35 noggins 4@5.1
lm
21
Damp Proof Course roll
No.
1
Nails and Dynabolts
item
First fix carpenters 2p x 2 day
hr
32
Miscellaneous
Total to summary
Rate
2.60
2.60
2.60
21.50
$
107
268
54
22
20
35.00 1120
100
$1 691
How many bricks per square metre of wall?
Standard brick size 230 x 76 mm
Mortar joints nominally 10 mm
Area taken up by one brick is 0.240 x 0.086 = 0.2064 m2
We get 1/0.02064 = 48.45 bricks/m2
For small areas round off to 50/m2 and add a %-age for waste
Tendering process
- Ensuring that you are invited to tender, if that is limited
- Taking the tender documents, which consist of drawing,
specifications and sometimes a bill of quantities, and breaking
them down into packages. These packages must be
appropriate for your subcontractors to bid for.
- Inviting subcontractors to bid and evaluating the bids.
- Adding up all construction costs plus the preliminaries or
overheads plus your margin to form the tender price.
- Finally, you need to submit the tender as per the instructions,
and don’t be late!