TAKE OFF’S
Quantity Take offs, the art of counting the intangible, the meticulous translation of a dream into a tangible reality of power and light.
But really… it’s the difference between a guestimate and an estimate.
Let’s get right in…
Take offs are all about breaking the project down into its individual pieces. It’s how we quantify the project to enable us to accurately calculate labor and material costs. Take offs are the difference between a guestimate and an estimate.
It is helpful to develop a standard way to approach each project with take offs which assists in breaking down the project into ‘bite sized chucks’.
Preparing:
1. Take Off Sheet
The process of take offs is first to have a take off sheet (paper or digital) something to record your data. This should include a line for each type of item and a column for the drawing on which it exists. Take Off Sheet.
** A few thoughts on take-off software. There are various software solutions that will do take offs automatically and no doubt these are handy time saving tools, however, these are tools only and this is not advisable if you are learning how to tender or are looking at a type of project you are not familiar with.
No matter the “100% guarantee” by the software sales team, it will make errors, usually errors of omission (miss something). It doesn’t matter if the cause of the error was user error or an error in the software itself, errors are much harder to pick up when unfamiliar with the manual process and principals of take offs, and with automation the error can be multiplied easily if not noticed.
Secondly you will not get the same immersion and familiarity with the project as with manual work, the difference between looking at photos on your phone of an open home and actually go to the open home and walking through it. Walking through the open home you pick up on all the small things, the leaking tap, the chipped paint, the missing light switch… things that would be missed by simply looking at photos.
The most relatable example I can think of is test and tag. Anyone can go do a 1 day course to use a test and tag machine… sure they can plug a lead in and read a result, are they an electrician? No. If there is an error they might have some basic knowledge of what it means or maybe even a simple how to fix it, but they have no idea and knowledge of the principals and calculations used to even come up with the testing criteria. And thus they can only see the smallest slice of a much bigger picture and therefore have very limited ability and skills to control the end outcome.
Give an electrician the same automatic testing equipment and sure it may speed up the testing from a standard meter, but they have a much deeper understanding and knowledge of what they are doing, why they are doing it, what they would expect the result to be and can explain why; and have the training, knowledge and skills to see, and understand errors, and to investigate further, and understand the cause, and fix problems competently, to control the end outcome.
With that being said, any automation is a tool, but make sure you know the manual methods and processes or you could get yourself into a pickle.
2. Drawing Cuts and Typical Areas
Before counting a thing have a quick look through the drawings as a whole. Make note of any cut lines and highlight these crossing out the section that is irrelevant to that drawing (is repeated on another) to ensure you don’t double up on the same item shown on two different drawings. Like wise, make note of any typical areas or drawings, particularly on apartment buildings or office high-rises where there are many duplicates of the same thing.
With typical areas, you want to take off the equipment in the typical area (room or apartment or level, or whatever it is) as an individual area. And then have a separate take off for all the times that each type of typical area appears in order to get the quantity for each typical area. Then multiply the number of the typical area with the number of items in the corresponding typical area to get the total number of items.
Start Counting:
1. Luminaires
It’s beneficial to generally start with luminaires. Luminaires are almost always the most numerous item, spread over the majority (if not all) of the project, and usually require the longest lead time for wholesaler pricing.
Completing the luminaire take offs first gives two benefits; it allows you to get a good feel for the project and allows you to send out pricing requests to wholesalers early in the tender process.
Pre-populating your take off sheet items column with the luminaire’s legend, usually just the symbols and abbreviation Letter/number that appears next to the symbol on the drawings is enough detail as you can reference the legend for the specific fitting details.
Linear lighting is best kept to its own take off sheet to allow for grouping of different lengths under the same fitting type.
Try to keep Emergency fitting grouped together for ease of reference.
Likewise with any lighting control, switches, motion detectors, PE, try to keep these grouped together for easy of reference.
2. General Power
Next get into the general power. Everything that has power, count it. Power accessories are pretty staring forward usually however pay attention to any special notes or requirements such as UPS or ESS power or finishes such as steel, accessible, IP ratings etc.
3. Sub-Circuits
There are a couple of different way to work out sub-circuits.
Manual Method: The manual method consists of manually measuring out each circuit, allowing for the route length and appropriate drop lengths at each fitting and switchboard.
Record each circuit length on a Take-Off sheet with cable size and switchboard and breaker number.
This method is usually used for projects where there is complexity and uniqueness across the project; that is a lack of uniformity and repetition. And gives the greatest detail especially helpful when designing the project also.
Calculation Method: The calculation method is taking the distance between the same fittings plus the drop length and then multiplying this by the number of that type of fitting and adding an estimated feed length multiplied by the number of circuits.
This method is very time efficient, especially for large projects that have simple design and uniformity across the project, such as an office block. The drawback obviously there is less detail and ability for design work with this method.
Both have pros and cons and use as suitable for each project.
4. Sub Mains
Measuring mains and sub-mains is much like the first method for sub-circuits. Work out the path of the sub-main and measure it; taking into account any vertical movement and terminations.
Start by designating each sub-main on the single line drawing with a number which can be used to identify that particular cable. Record the route length next to each number.
Keep in mind that when entering this information into your data base you will need to multiply your route length by the number of physical cables to be installed in order to get the actual meters of cable required to make that circuit.
For example: a 100m route length of 4 x 1C 120mm2 XLPE + 35mm2 E sub-main will require 400m of 120mm2 SDI XLPE cable and 100m of 35mm2 Earth cable. Whereas if this was a 100m route length of 1 x 4C 35mm2 + E it is just 100m of 35mm2 4C+E.
Accuracy in key as every meter can be a significant cost.
5. Switchboards
Switchboards will either be designed or not designed. We will cover the design in our design section.
For take offs it simply matching up with is shown on the singe line with the drawings which will be pretty much complete after having done the sub-mains.
6. Cable support
Cable support can be anything from in-ground works, conduits in slab to cable trays.
Focus on one type of cable support at a time (that is for example to do all the inground works, then move on to all the in slab work, then all the cable tray supports etc.) this helps with keeping things simple and systematic.
In-ground works: This it is a similar process to the sub-mains in which your main focus will be with linear meters and type. Identify each type of trench: Type 1 might have 6 x 100mm E and 2 x 100mm C conduits and be a physical size of 750mmW x 800mmD; Type 2 may be 1 x 32mm E and 1 x 25mm C trench 300mmW x 600mmD. Then measure the linear meters of each type; Type 1 = 250m, Type 2 = 150m.
Then multiply them out:
Eg. Trench 1:
- 250m Trenching
- 250 x 0.75 x 0.8 = 150m3 excavation
- 250m x 0.75 x 0.15 = 28.13m3 of sand
- 250m x 3 E tape = 750m E warning tape
- 250m x 1 C tape = 250m C warning tape
- 250m x 6 100mmE = 1500m of 100mmE Conduit
- 250m x 2 100mmC = 500m of 100mmC Conduit
*Don’t forget bends, pits and route markers… count these as required.
Cable Tray: Same process again; measuring linear meters per type. Depending on the size and complexity of the installation it can be helpful to measure and mark the linear length of each section (type) of tray on the drawings, then take off the total meters of each size of tray one size at a time.
7. Sub-Trades
Taking off any final sub-trade items which you are either providing directly or subcontracting out. Such as comms, security, dry fire, AV etc.
Usually this will be the last thing to look at as you are either only providing support works such as cable containment and will have sent a quote request or being standalone works that don’t really have an effect on other parts of the electrical works.
Final Review
Have a look back through the drawings and specification looking for any notes, additional items (spares or documented additional items), and any possible missed items not taken off.