The critical path: Just how critical
You’ve probably heard the term “critical path”
many times. But what does it really mean and how can it
help or hurt you when it comes to delay claims on a project?
The standard nearly all courts recognize what is known as
the Critical Path Method (“CPM”) as the most
readily accepted method of measuring project delays. CPM
is the benchmark that is universally accepted in construction
delay claims litigation.
It is extremely important for anyone
involved in construction to understand how CPM is used for
proving delay claims. If you don’t know how a delay
is measured, you may find it difficult proving you were
really damaged by a delay. Or worse yet, you may find it
difficult defending yourself against an unfair delay claim.
A quick history Commonly known by its initials “CPM,”
it is a method of estimating how long a project will take
to complete. A critical path is determined by taking the
key tasks in sequence and adding up the longest time necessary
to complete all the tasks to determine the project’s
total length. The procedures are the same for small projects
or large projects, but larger projects will benefit from
the use of project management software, since the software
can handle hundreds of tasks and variables with ease.
project management software uses a variant of CPM called
PERT, which means Program Evaluation Review Technique. PERT
was developed in 1958, a year after CPM was first used,
but the name CPM has become synonymous with both methods.
What distinguishes PERT from pure CPM is its use of statistics
to predict completion times. Using three time estimates,
optimistic, pessimistic and most likely, a more realistic
completion time estimate is created.
The basics here is
a quick primer on what it takes to create a CPM schedule.
CPM is focused both on time and sequencing. First, a sequence
of work is determined. Then, assign each sequence a time
interval required to complete it and theoretically you have
a critical path. You need to know the following information
in order to create any sort of CPM schedule:
1. Specific activities: These are unique tasks that have
a distinct length of time for completion. In construction,
these are usually straightforward and fairly easy to identify
2. Milestones: These are events that
identify the beginning or end of a task.
3. Sequence: Getting from bare
earth to a finished building requires
the proper sequence of construction
tasks. Some sequences are obvious,
and others are not. For example, it is
clear that earthwork must come before
roofing. But, it may not be so obvious
whether finishing the plumbing would
come before or after roofing, or
whether it really matters.
4. Dependent tasks: Careful analysis is
often needed to determine the cause and
effect relationships between tasks. Tasks
that depend on the completion of another
task must be identified.
5. Time estimate: The time required
for each activity is needed. An experienced
estimator can shoot from the hip
and use past experience as his guide,
but often input from each trade is
needed to get realistic estimates of time
for their work. It is at this point that
PERT-type statistics would come into
play (whether calculated manually, or
generated by project management software)
in order to arrive at the best estimate<
for a task time.
With the above information available,
a project diagram can be created. Laid
out graphically, all the milestones
(events) are connected together by a network
of activities (tasks) to visualize the
entire project from beginning to end.
The critical path would be the longest
duration of tasks that must be done in
sequence in order to get from the
beginning to the end. There may be
tasks that can be performed in parallel
with other tasks.
There may be tasks that can be performed
at any time after achieving a certain
milestone but have no specific start
date, only a required completion date.
The difference between the time allocated
to perform the task and duration
of the task is commonly known as float
or slack time. All tasks on the critical
path have no slack time.
The real world-
Once a project is planned out and a
critical path defined, there is no guarantee
that the course of the project will
actually follow the plan. A few examples
of why this can happen are:
• Estimates: One of the simple reasons for a schedule
deviation is that everything is based on estimates. The
schedule is only as good as the quality of the estimates,
and for the most part, the people who created the estimates
are not the people who actually perform the work.
• Changed conditions: If actual conditions are different
from those expected at the time estimates were determined,
those estimates may not be realistic.
• Change orders: Almost without exception, projects
will have change orders. What needs to be considered very
carefully is whether or not the change orders affect just
a specific task schedule or the critical path.
Making CPM work for you- Keep in mind though, that just
because there may be change orders, changed conditions,
sloppy estimating or anything else that causes a delay,
if the delays do not affect any of the critical path tasks,
the project as a whole, is not delayed.
Also, applying additional resources
to activities that are not on the critical
path may allow them to be completed
early, but it won’t benefit the overall
project end date.
Remember, improving the estimated
completion date, or getting a project
back on track to finish by the promised
date, depends on your ability to identify
and shorten the tasks or activities that
are on the critical path.
If you have a construction question, submit it to: info@construction-laws.
• • •
Disclaimer The information in this article is based upon
California law and is for general information only. Any
information or analysis presented here is intended solely
to inform and educate the reader on general issues. Nothing
presented or referenced to, regarding facts, documents or
applicable laws, constitutes legal advice. Before acting
or relying on any information, including any information
presented here, consult with a qualified attorney for your
Scholefield, Esq., holds an active PE license in Colorado,
an undergraduate engineering degree from the University
of Florida, and received her JD from the University of San
Diego. Source Code: 20080314tca
Call us now to discuss how you can benefit
by using a different approach to managing to your legal
Njia muhimu: Jinsi muhimu wewe pengine kusikia neno "njia muhimu" mara nyingi. Lakini ni nini hasa maana yake na jinsi gani inaweza kukusaidia au kuumiza wewe linapokuja suala la kuchelewesha madai juu ya mradi? "Kwa mujibu wa sheria za nchi, ""Critical Path Method"" (CPM) ni njia ya kawaida ya kupima ucheleweshaji wa mradi." CPM ni kiwango cha msingi ambacho kinakubaliwa ulimwenguni katika madai ya ucheleweshaji wa ujenzi. Ni muhimu sana kwa mtu yeyote anayehusika katika ujenzi kuelewa jinsi CPM inavyotumiwa kuthibitisha madai ya kuchelewesha. Kama hujui jinsi ucheleweshaji hupimwa, unaweza kupata ni vigumu kuthibitisha wewe walikuwa kweli kuharibiwa na ucheleweshaji. Au, hata zaidi, huenda ukaona ni vigumu kujilinda dhidi ya madai ya kuchelewesha isivyo haki. Kwa kawaida inajulikana kwa herufi zake za kwanza <unk>CPM,<unk> ni njia ya kukadiria ni muda gani mradi utachukua kukamilika. Njia muhimu ni kuamua kwa kuchukua kazi muhimu katika mfululizo na kuongeza muda mrefu zaidi muhimu kukamilisha kazi zote kuamua urefu wa jumla wa mradi. Utaratibu ni sawa kwa miradi midogo au mikubwa, lakini miradi mikubwa itafaidika na matumizi ya programu ya usimamizi wa mradi, kwani programu inaweza kushughulikia mamia ya kazi na vigezo kwa urahisi. Programu ya usimamizi wa mradi hutumia aina ya CPM inayoitwa PERT, ambayo inamaanisha Ufundi wa Mapitio ya Tathmini ya Programu. PERT ilianzishwa mwaka 1958 baada ya CPM kutumika kwa mara ya kwanza, lakini jina CPM limekuwa sawa na mbinu zote mbili. PERT inatofautishwa na CPM safi kwa sababu ya matumizi yake ya takwimu kutabiri nyakati za kukamilika. Kutumia makadirio matatu ya wakati, matumaini, pessimistic na uwezekano mkubwa, makadirio ya muda wa kukamilika ya kweli zaidi huundwa. Kwa ufupi, hii ni orodha ya msingi ya kile kinachohitajika ili kuunda ratiba ya CPM. CPM inahusu wakati na utaratibu. Kwanza, utaratibu wa kazi huamuliwa. Kisha, weka kila mfululizo kipindi cha muda kinachohitajika kukamilisha na theoretically una njia muhimu. Unaweza kupata maelezo yafuatayo ili kuunda ratiba ya CPM: Shughuli maalum: Hizi ni kazi ya kipekee ambayo ina urefu tofauti wa muda kwa ajili ya kukamilika. Katika ujenzi, hizi ni kawaida moja kwa moja na rahisi kabisa kutambua 2. Milestones: Hizi ni matukio ambayo kutambua mwanzo au mwisho wa kazi. 3. Uwe na mtazamo wa kweli Kuanzia ardhi tupu hadi jengo lililokamilika, kazi za ujenzi zinahitaji kufuatana kwa utaratibu. Baadhi ya mfuatano huo ni dhahiri, na wengine si dhahiri. Kwa mfano, ni wazi kwamba kazi ya udongo lazima ianze kabla ya paa kufanywa. Lakini, inaweza kuwa si hivyo dhahiri kama kumaliza plumbing ingekuwa kuja kabla au baada ya paa, au kama ni kweli muhimu. 4. Uwe na uhakika Kazi zinazohusiana: Uchambuzi wa uangalifu mara nyingi unahitajika ili kuamua uhusiano wa sababu na matokeo kati ya kazi. Kazi ambazo zinategemea kukamilika kwa kazi nyingine lazima zitambuliwe. 5. Uwe na mtazamo mzuri. Wakati wa kukamilisha: Wakati unaohitajika kwa kila shughuli. Mtakadiriaji mwenye uzoefu anaweza kupiga risasi kutoka kwenye kiuno na kutumia uzoefu wa zamani kama mwongozo wake, lakini mara nyingi pembejeo kutoka kwa kila biashara inahitajika kupata makadirio ya kweli ya wakati wa kazi yao. Ni katika hatua hii kwamba PERT-aina takwimu ingekuwa kuja katika kucheza (kama mahesabu manually, au yanayotokana na programu ya usimamizi wa mradi) ili kufika katika makadirio bora kwa ajili ya kazi ya muda. Pamoja na habari ya juu inapatikana, mchoro wa mradi unaweza kuundwa. Ili kuelezea kwa njia ya picha, hatua zote (matukio) zimeunganishwa pamoja na mtandao wa shughuli (kazi) ili kuiona mradi mzima kutoka mwanzo hadi mwisho. Njia muhimu ni muda mrefu zaidi wa kazi ambazo zinapaswa kufanywa kwa mfululizo ili kupata kutoka mwanzo hadi mwisho. Kunaweza kuwa na kazi ambazo zinaweza kufanywa sambamba na kazi nyingine. Kunaweza kuwa na kazi ambazo zinaweza kufanywa wakati wowote baada ya kufikia hatua fulani lakini hazina tarehe maalum ya kuanza, tarehe ya kukamilika inayohitajika tu. Tofauti kati ya muda uliotengwa kutekeleza kazi na muda wa kazi ni kawaida inajulikana kama kuelea au muda wa kuteleza. Kazi zote juu ya njia muhimu hawana muda wa kuteleza. Katika ulimwengu halisi, mara tu mradi unapopangwa na njia muhimu imewekwa, hakuna dhamana kwamba mwendo wa mradi utafuata mpango huo. Mifano ya sababu hii ni: • Makadirio: Moja ya sababu rahisi kwa ajili ya kupotoka ratiba ni kwamba kila kitu ni msingi juu ya makadirio. Wakati wa kuandaa ni bora kama ubora wa makadirio, na kwa sehemu kubwa, watu ambao waliunda makadirio sio watu ambao hufanya kazi. • Hali iliyobadilika: Ikiwa hali halisi ni tofauti na zile zilizotarajiwa wakati makadirio yalipoamuliwa, makadirio hayo yanaweza kuwa ya kweli. • Marekebisho ya maagizo: Karibu bila ubaguzi, miradi itakuwa na mabadiliko ya maagizo. Nini inahitaji kuchukuliwa kwa makini sana ni kama au si amri ya mabadiliko kuathiri tu maalum kazi ratiba au njia muhimu. CPM inaweza kuwa muhimu kwa ajili ya kazi yako, lakini kumbuka kwamba tu kwa sababu kuna mabadiliko ya amri, mabadiliko ya hali, makadirio sloppy au kitu kingine chochote kinachosababisha kuchelewa, kama kuchelewa si kuathiri yoyote ya kazi muhimu njia, mradi kama nzima si kuchelewa. Pia, kutumia rasilimali za ziada kwa shughuli ambazo si juu ya njia muhimu inaweza kuruhusu wao kukamilika mapema, lakini si faida ya jumla ya mradi mwisho tarehe. Kumbuka, kuboresha tarehe ya kukamilika inayokadiriwa, au kupata mradi nyuma kwenye kufuatilia kumaliza kwa tarehe ya ahadi, inategemea uwezo wako wa kutambua na kufupisha kazi au shughuli ambazo ziko kwenye njia muhimu. Ikiwa una swali la ujenzi, lipe kwa: info@construction-laws. • Taarifa katika makala hii inategemea sheria ya California na ni kwa ajili ya habari ya jumla tu. Taarifa yoyote au uchambuzi uliotolewa hapa unakusudiwa tu kumjulisha na kumfundisha msomaji juu ya masuala ya jumla. Hakuna kitu kilichowasilishwa au kutajwa, kuhusu ukweli, nyaraka au sheria zinazotumika, huunda ushauri wa kisheria. Kabla ya kutenda au kutegemea habari yoyote, ikiwa ni pamoja na habari yoyote iliyotolewa hapa, wasiliana na wakili wa sifa kwa Scholefield, Esq. ambaye anashikilia leseni ya kazi ya PE huko Colorado, shahada ya uhandisi ya shahada ya kwanza kutoka Chuo Kikuu cha Florida, na alipokea JD yake kutoka Chuo Kikuu cha San Diego. "Kifungu cha ""Kufanya kazi"" cha 2008: ""Kufanya kazi"" ni njia ya kuelezea jinsi ya kufanya kazi kwa njia ya kisheria."