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Project Duration

12 replies [Last post]
Vishwas Bindigana...
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Hi Everybody,

Can anyone tell me how to decide on the duration of a project? Is there a thumb-rule used in the market by proffessionals? Is it based on the following -
Region, Built-up area, Type of building, Materials used, etc.?

Replies

David Bordoli
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Hey Speedy...

Are you sure the cold isn’t getting to you out there in Antarctica... I am afraid I didn’t understand a word of that!

David
Vishwas Bindigana...
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Thanx David,

That was mind-boggling info.

Regards,

Vishwas
Dayanidhi Dhandapany
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Dear David,

Thanks for sharing some interesting information on Project duration.

Cheers!!!

Daya
David Bordoli
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Dear All

Okay, a serious answer now… This is the text from an article in the UK magazine ‘Building’ (www.building.co.uk:

Time machine
Completion dates in contracts are more wishful thinking than statement of fact. But what if you could predict the actual time it takes to construct buildings? We look at an aid that’s supposed to transport clients and consultants into a more certain future.

2 July, 2004
By Andy Pearson

How long will it really take to build? Clients everywhere are desperate to find out the answer to this simple question. But in many cases, predicting the duration of construction, and therefore the likely cost to the client, tends to be way off the mark. In fact the DTI’s figures show that almost 40% of construction projects over ran their contact period in 2003.
The problem is that most historical information on project duration available to clients and consultants has been based on the time period stated in the contract and not on the actual time the project took to build. In other words, from the day work started on site to the date of practical completion when the building is handed over with only minor defects.

Now the RICS’ Building Cost Information Service has produced a guide on the actual time taken to construct a building based on its cost and a few key project variables, such as procurement route, client type, project sector, building function and region (all of these are listed in the table opposite). To keep things simple, the guide includes a CD, which allows users to predict the likely construction time for their building.

For a copy of the guide and CD, contact BCIS through their web site at www.bcis.co.uk


If you are a registered user you can see the article on-line along with some typical data tables; graphing those and doing some regression analysis provides a simple tool for estimating activity duration. I imagine the CD that accompanies the book is far more comprehensive.

For those that are interested the book and CD is called ‘Guide to Building Construction Duration’, ISBN 1904839 05 8 and costs GBP 95 + VAT and was published May 2004. It is available from:

BCIS
3 Cadogan Gate
London
SW1X 0AS UK.

Tel +44 (0) 207 695 1500
Fax +44 (0) 207 695 1501
Email sales@bcis.co.uk

Regards

David
david.bordoli@gvagrimley.co.uk
Bernard Ertl
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Vishwas, that is a form of conceptual estimating. There are commercial conceptual cost estimating systems available, but they all more or less require you to define a set of criteria (equipment costs, dimensions, conditions, etc.) and then they extrapolate or calculate an estimate based upon an analysis of a database of historical projects.

Bernard Ertl
InterPlan Systems - eTaskMaker Project Planning Software
Vishwas Bindigana...
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Hi Fellow-Planners,

I was expecting more number of members to participate in this discussion as I feel this is a very interesting topic and quite tricky. I was also following-up with the replies posted, and I sincerely thank you guys for your expertise.

I have been observing the market in India and UAE for the last six years as a Planning Engineer. Please allow me to share my view-points on this matter. Apart from the experience, guess-work, assumptions, critical path analyses, etc. which are the deciding factors in the calculation of the duration of the projects, I have come across some basic ratios which form the detrimental factors for the total duration irrespective of the slab-to-slab cycle, type of structural slab, floor or height, region, etc.

The following would be helpful for you guys to analyze –

1. Substructure - The duration of this item would comprise about 20-25 percent of the total project duration. This excludes enabling and earthworks like shoring and basement excavation.
2. Superstructure - This would generally make-up 40-45 percent of the total project duration. This excludes parapets and other miscellaneous structural works at the roof.

The duration lag for the superstructure from the substructure would depend on the type of substructure and the total nos. of basements in it. For example, if we have a 10-storey building with one basement; the sub-structure would be around 15 days (including ground slab) and the superstructure would be around 120 days. Hence, the total project duration would be somewhere around 300-320 days including the internal & external finishes, MEP works, fittings & fit-outs, etc. The enabling works and the landscaping and road works’ duration will be an add-on to the total duration.

This primitive ratio is applicable to high-rise buildings, commercial & residential complexes and other such buildings where vertical movement is more than horizontal movement.

For projects spread across a large area like industrial buildings, hospitals, institutional campuses, etc. the percentage of substructure and superstructure would be almost equal to that of the finishes.

Hope this is good food for your thoughts. Can anyone throw light on durations for projects of infrastructure (bridges, dams, STPs, etc.) and other types?

Happy Planning.

Vishwas
Shahzad Munawar
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Currently no thumb rule is available to estimate the duration of project.

Duartion is usually evaluted on Planner’s experience keeping in view the Project frame work (type of project).
David Bordoli
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.
David Bordoli
User offline. Last seen 3 years 21 weeks ago. Offline
Joined: 8 Apr 2002
Posts: 416
I read recently of a method that is used almost universally; Its called ‘guessing’. Obviously it’s not as straight-forward as it sounds because there are a number of enhancements to the basic method:
 guessing,
 informed guessing,
 experienced guessing,
 team guessing

:-)

Regards

David
david.bordoli@gvagrimley.co.uk
Andrew Tan
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Dear Vis,
There is no actual thumbrules for scheduling. It depends largely on the project scope and experience of the estimator.
That is why estimator is important to give a duration. Otherwise, you need the Methods Statement from bottom up to get a feel of duration.

Experience counts in this industry.
Dayanidhi Dhandapany
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Dear Vishwas, If you insist on thumb rule, i could tell something about it in buildings. Based on my experience in Malaysian construction industry, they follow floor cycle something like 7days, 10days and 14days etc to move on to next floor(The duration varies based on the formwork type/resources/floor area etc). Just for an example if you know the maximum number of floors in Building blocks(say Block A, B, C etc..), based on the floor cycle you can roughly estimate total duration required to complete structural works, then in the same manner calculate the total duration required for external architectural finishes if any. Then add all these duration with time required for foundation works(Note: All these durations will be on the longest critical path), based on your scope of works that will form the project duration. I hope the above will satisfy something about your requirements. Regards Daya
Bernard Ertl
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If you plan and schedule the work, the critical path (and any risk analysis you employ) should give you a good indication. If you do not plan and schedule the work, you need to use your best guess or some form of conceptual/high level estimating.

Bernard Ertl
InterPlan Systems - eTaskMaker Project Planning Software