Lecture 2 Flashcards
What are types of estimation methods in constructuon?
- Material
- Labor and equipment
- Job overhead (plant cost)
- Generar overhead and profit
- Contingencies
Conceptial Estimates
- 2 factors come into play, they are Cost and Value
- estimates are usually around +/- 30% accuracy.
-Created at the initial stages of the project. They are little more than a basic attempt to understand what the final costs could eventually be.
Are created using very basic principles like:
o Square area methods (ft2, m2)
o Volume methods (ft3, m3)
Sometimes created on a napkin
Preliminary Estimates (design development estimates)*
-prelim estimates can reach final costs accuracies of +/- 15%
- As the design progresses, the design teams may see opportunity to
economize the project in terms of alternate construction materials or labor
and equipment. Changing from a concrete envisioned structure to either
wood or steel is an example of such.
-
Detailed or Pre-tender Estimates
- The final and most accurate estimate of the project costs.
- Accuracies can be as high as +/- 3-5% of the actual costs.
- Done by the owner’s representatives or quantity surveyor (QS).
- Every bidder will create a detailed estimate depending on the time an effort
they put into the work. Obviously, the more time allowed the more accurate
the estimate. - Bidders with many years of construction experience tend to have the most
accurate bid estimates. This is due to a long history of creating estimates
and excellent data keeping of previous estimates that are used for future
reference.
Design – Bid – Build
DBB
In the DBB, the owner hires a prime consultant, usually an architect, to help them envision the project and produce conceptual drawings that can be used to hire other professionals like engineers, etc. The design team then works on the project using preliminary estimates to control costs and get the best deal for the owner. After some time, the designs are completed and the owner or their representative for bidding purposes distributes the drawing package and specifications. Contractors are asked to bid on the project and provide a timeline and total cost to complete the work.
This system is typically the slowest in terms of concept date and final turnover date. In terms of risk. The owner is usually in a safe situation, monetarily wise, as they have been provided a firm contract price. The successful bidder is bound by the terms of the system and contracts included, so their estimates have to be very accurate, or they stand to lose a lot of money.
Construction Management Delivery System (CMD)
This system is one of the fast-track types, which means the time line to complete the project can be shortened.
In this system, the owner hires the design team along with a project management team (Construction management company, or CMC) to help design and oversee the project. This allows the project management team to be included at the beginning of the project and have their input included in the overall design. Their experience and knowledge are valuable in the design process. In this system the project can be broken down into phases. This way work can begin earlier than in the DBB system. For example. In the DBB, excavations cannot start until the design have been completed and bidding has been awarded. In the CMD system excavations can be occurring whilst the design team works on the structure. A valuable shortening of the timeline can be appreciated.
Design Build System or DB
This is another fast-track system.
In this system, the owner hires multiple construction companies who then put together
a team of design professionals to create the building or structure. To begin, the
owner will specify a basic needs package of what they want. The project is usually
simple in nature and the owner only wants a project to satisfy some simple basic
needs. Roads, public building like sports facilities are examples.
Once each company has a design package, they are submitted to the owner for their
perusal. The owner then picks the best design for their purposes and awards that
contractor the job.
Common system where the owner is not that concerned with the projects overall look
so long as it functions as intended.
. Lump Sum
As noted above in the delivery systems portion. Lump sums contracts are
prices for a set final cost to perform the work.
They are safe for certain parties but not others in terms of extra fees
incurred.
The contracts usually provide some accommodation for parties in case of
rising costs, or other unforeseen circumstances.
. Cost Plus
As the name implies, these are contracts for the work as it relates to the
costs of materials, labor and equipment plus a specified profit for the
contractor.
Used almost exclusively by contractors involved in remedial work or
renovation work. Eg. Contractors that provide repair services for damages
due to climatic events…
Unit Price
Safe for all parties as it is a cost based on an agreed upon amount prior to
construction.
Used almost exclusively by the excavation trades, as the subsurface
conditions are very hard to be certain of and extra costs could drive the
company into bankruptcy.
Also used in terms of items like bathroom or electrical fixtures.
What are some hidden costs?
- Travel, accommodation, staff expenses, crew transportation, etc.
- Temp offices, facilities, office equipment, lunchroom for crews, etc.
- Temp site services, electric, water, sanitary, etc.
- Weather, climate influences on productivity, snow removal
- Temp enclosures (hoarding and heating)
- Security, fencing, watchman.
- Equipment rentals, storage, site prep & cleanup.
- Printing, signage.
- Other?
Construction safety per WCB Regulations
- Safety / First Aid (crew size, types, # of attendants, ambulance)
- Trenches, Pits, etc…
- Formwork, Scaffolding, Shoring (does false work need Eng seal?).
- Guard-rails, rebar pro, fall restraint, fire suppression, admin costs, certs, etc.
- Training crews, Liability insurance, WCB payments.
- Other?
