For tasks related to the design, such as estimating, coordination and scheduling, paper plans and specifications are the typical starting point, even if the architect used 2D or 3D CAD systems for the design. These require contractors to manually perform quantity take-offs to produce an accurate estimate and schedule, which is a time consuming, tedious, error prone and expensive process.[1]

As it says above, there are difficulties for contractors that they face each project, but it seems that BIM can be big of a help:

The quantity and cost estimation is better to be made during the design process. It will be very unfortunate to find out after all made decisions in the scheme phase that project is over the budget. BIM model not only offers alternative choices that could help in reducing the cost and enhance the quality of the project but also improve collaboration and accuracy between design and construction team. Especially when the contractor recalculates the required component amount for cost estimation during bidding. It requires time, however if the client would offer BIM model with required information, the contractor could concentrate time not on counting but optimizing the choice of building components and minimizing the project expenses.

As it is written in (Eastman, Teicholz, Sacks, & Liston, 2008) p.224 about traditional method:

Scheduling is therefore a manually intensive task, and it often remains out- of -sync with the design and creates difficulties for project stakeholders to easily understand the schedule and its impact on site logistics.

That means that traditional method again takes time and creates problems for project participants. However:

The construction of the 4D models enables the various participants (from architects, designers, contractors to owners) of a construction project, to visualize the entire duration of a series of events and display the progress of construction activities through the lifetime of the project.(Introduction to 4D Research.Retrieved from Stanford University: http://web.stanford.edu/group/4D/)

4D BIM tools offer the possibility of using building components with time properties, so that it allows to create planning schedules with visual simulations that can be used for site logistics, visual communication of the planned construction process between all contractors, tracking construction process and etc. This will improve collaboration and planning on the building site between different contractors.

Today, many types of building components are produced and/or assembled offsite in factories and delivered to the site for installation. BIM provides the capability for contractors to input BIM component details directly, including 3D geometry, material specifications, finishing requirements, delivery sequence, and timing, etc. before and during the fabrication process.[2]

This statement not only proves that BIM can improve better information channel between design team and contractors who manufacture specific building components but also more accurate time of transportation. Also that could reduce the time for storing the building component on site so the quality of them doesn’t drop and reduce expenses for keeping the building components in the manufacturer storage area.

Clash detection is an important operation to use in a design process as it is reducing the errors during the construction of the building. It identifies overlapping of the building components and gives opportunity to solve the problems before the mistake is made. If we refer to the traditional 2D drawings, it takes a lot of time to manually discover all the clashes. It also can be prone to error and require up to date drawings.

On the other hand 3D BIM can automatically identify the clashes and visually present it to the contractors. The clashes can be categorized by the type of components so each individual contractor can see their field of interest. However the model should be accurate to ensure that there will be no problems such as wrong piping, ducts and structure sizes.