May 09

Composite Rate Build Up for Rainwater Downpipes – Approximate Quantities in Elemental Estimate Layout

 

CompositeRate_Rainwater Downpipes

Composite Rate Build up – Rainwater Downpipes

The Elemental Estimate layout and grouping of items will be used in this example. When building up composite rates for Approximate Quantities, you have to follow some basic principles. We are going to illustrate a composite rate build-up for Rainwater Downpipes:

0,6mm Galvanised sheet iron Class Z 275

  1. 75mm Diameter rainwater downpipe 3000mm long with brackets fixed to brick wall or concrete.
  2. Extra over rainwater pipe for shoe (plinth offset) – No 12
  3. Extra over rainwater pipe for eaves offset – No 12
  4. Prepare, prime with a self-etching primer and apply one coat universal undercoat and one full coat high gloss enamel paint for exterior use:  On galvanised sheet iron Class Z 275 rainwater downpipes.
  5. Extra over Eaves gutter for stopped end – No 12
  6. Extra over Eaves gutter for outlet with nozzle for and jointed to 75mm diameter galvanised sheet iron downpipe including galvanised wire balloon grating – No 10

Step 1

First, you have to determine the Group unit of measurement. When you are measuring Rainwater Downpipes in Elemental or Approximate Quantities estimating, the group unit of measurement is the metre (m).

Step 2

The second step is listing all associated Bill items that can be mapped to Rainwater Downpipes by length. These are:

  • Galvanised sheet iron 75mm diameter Rainwater downpipes  – (m) Rate – R50.00
  • Two coats emulsion paint and one coat primer on Rainwater downpipes – (m) Rate – R36.00

Step 3

The third step is listing all associated Bill items which are linked to Rainwater Downpipes, but which cannot be mapped to downpipes by length:

  1. Extra over rainwater pipe for shoe (plinth offset) – (No) Rate – R50
  2. Extra over rainwater pipe for eaves offset – (No) Rate – R60
  3. Extra over Eaves gutter for stopped end – (No) Rate – R45
  4. Extra over Eaves gutter for outlet with nozzle for and jointed to 75mm diameter galvanised sheet iron downpipe including galvanised wire balloon grating – (No) Rate – R15

Step 4

Rate Build Up for items which can be mapped by length. Since your Group unit is the metre (m), you should convert the Bill item rates to Cost per Metre.

Rate Build Up

GROUP – DOWNPIPES

Rate – Cost Per Metre (m)  Rands
1m of Galvanised Iron Rainwater Downpipes    
1m = R50 50
1m of Paint on Rainwater Downpipes
1m = R36 36
Composite Rate – DOWNPIPES 86  

The composite rate for items which can be mapped to the Downpipe by Length is R86 per metre.

Step 5

Rate Build Up for items which are linked to the Rainwater downpipe, but which cannot be mapped to downpipes by length:

Rate Build Up

GROUP – DOWNPIPES

Rate – Cost Per Metre (m)  Rands
Extra over Rainwater Downpipe for Shoe    
1 Downpipe has one shoe (plinth offset) = R50
3000mm = R50
1000mm = 3000/50
1000mm = R16.67 16.67
Extra over Rainwater Downpipe for Eaves Offset
1 Downpipe has one eaves offset = R60
3000mm = R60
1000mm = (1000×60)/3000
1000mm = R20.00 20
Eaves gutter Outlet with Nozzle and Jointed to Rainwater pipe incl. Galvanised Wire Balloon Grating
1 Downpipe is joined to one Gutter Outlet = R15
3000mm = R15
1000mm = (1000×15)/3000
1000mm = R5.00 5
Stopped End
Count number of stopped ends – they are found close to downpipes at the corners of the building where the gutter ends, say 4 No.
3000mm x 4 = 12,000mm
4 stopped ends = R45 x 4 = R180
12000mm = R180
1000mm = (1000×180)/12000
1000mm = R15.00 15
Composite Rate – DOWNPIPES 56.67  

The composite rate for items which cannot be mapped to the Downpipe by Length is R56.67 per metre.

Step 6

Total Composite Rate for Downpipes is (86+56.67) = R142.67

Elemental Layout and Grouping

Items which go into the element ROOF and component Downpipes are stated in the description below:

 

 

Unit Quantity Unit Rate Cost/m2 Subtotal Cost
ROOF
Downpipes:
Galvanised sheet iron 75mm diameter Rainwater downpipes  including stopped ends, outlets with nozzle, shoes, eaves offset and painting.

 

M 142.67
Subtotal Downpipes