Introduction

Welcome to our online course – BIM Basics for Quantity Surveyors and Cost Estimators. The course is centered around the understanding of key aspects of BIM so you can take full advantage of this methodology in your own workflows. The content is split into three sessions that will be recorded and you will be able to watch them on demand. Everyone that enrolls in this course will receive a test at the end to get a BIM basics certificate from Bimmetry and Glodon Singapore.

1st Session – BIM modelling for QS 

2nd Session – BIM management for 5D BIM

3rd Session – Take advantage of BIM on your next QS/ cost estimation project

The course is organized by Bimmetry and Glodon Singapore.

Recording – Session 1 – BIM Modelling for QS

 

Session 1 Content:

So let`s start with what is actually BIM or Building Information Modelling. The keyword here is information. When we talk about 3D modelling, we usually call it 3D modelling, but in the case of BIM we have 3D models and information, or meta-data linked to the 3D geometry. This information is indeed quite useful and gets used in various processes and programs through the lifecycle of the building. Another important abbreviation to be aware of when we talk about BIM is LOD or the Level of Development of the components. The scale on which we measure LOD is 100 to 500. NATSPEC have an especially useful document for the definition of LOD if you want to learn more. But let us quickly explain the scale – When we say a model is in LOD 100, we usually mean it is still in concept design. And this means that there are components, but it is not their final version. If we pick an example with a chair – we have put an object of a chair, but it is still far from the actual chair that would be placed. LOD 200 is the Design Development model. LOD 300 or LOD 350 are the models we use for Construction documentation. LOD 400 is model from which we can fabricate, so we have all the nuts and bolts in it. And LOD 500 is as-built BIM model. As we mentioned in BIM we have additional information and one parameter of this meta-data is usually cost. If we have prices in the BIM models depends on the LOD. In LOD 100 we cannot expect to have cost parameters filled in yet. Usually we make per sq.m. estimates based on the BIM model. In LOD 200 we can extract the quantities from the BIM models and give some approximations. Often for LOD 300 or LOD 350 we have requirements for the data in the BIM models, and you could have specific data and prices filled in the meta data for the objects. In LOD 400 we are expected to have the actual prices linked to all components in the BIM models. And in LOD 500 we have the actual operation and maintenance cost. Why do we mention all this? Because as QS and cost estimation professionals you might get a BIM LOD 350 model with all these prices filled in by the design consultants based on the specification and not even realize it. You might want to have your estimates and pricing done your way, but still this is useful information to compare to.
In the first scenario you get a new project and you know there is a BIM model, but you have no idea what is the quality of it, what is the LOD – level of development, how recent it is. Well, in this case – what you should do is to check the model. And further in the course we will discuss what you should be mindful of and what kind of problems you might be able detect and look for when you make your checks. In the second scenario you might have BIM models that you are very certain of in terms of quality. You also know there is not only 3D geometry, but additional data attached to the models such as cost. You might go forward with more confidence and directly extract the quantities and the estimates, but still you might want to use a tool as Cubicost, in order to get extra quantities like reo and formwork, get automated deductions and format the estimates in the way you want. In the third scenario the design consultants might have issues with sharing their models. This is because they might have their own BIM content created which comes with copyrights and IP, but there is a work-around this. As you don`t need their content except for the quantities from it, you can just use Cubicost for example to import their model or ask them to import it themselves and then use the BIM model directly in Cubicost, which is not anymore a native Revit format anymore and the consultants IP and copyrights are protected and in the same time you have managed to do your job. So, it is all a matter of discussion, just make sure when a consultant doesn`t want to share their model to ask for the reason behind this. As there might be a simple solution that works for everyone as I just mentioned.
Now, let us have a look at the BIM model uses. Why everybody needs these models and what they can do with them? In the conventional design-build process before BIM all the 3D models and 2D drawings were mostly of an interest during a certain phase of the design-build process, the case with BIM is slightly different – the BIM models can be of use during the whole lifecycle of the building and number of stakeholders are interested to have the models. That is why we need to start with the end in mind. During operations, the BIM model becomes a sort of a dossier for the building. You can use various software where your BIM model becomes digital replica of the physical asset and to each component you can attach various maintenance information. You can get notifications for certain objects that need maintenance and see in a web browser in the BIM model exactly what and where needs to be fixed. There are a lot of tools that can make the models useful for the Facility managers, the owners, and the final inhabitants of the spaces. Even without specialized FM software having the BIM model can help for the future maintenance, renovation, and reconstruction. By simply opening the model and seeing where the installations are, who installed the items and when, the manufacturers and the cost – anyone that is responsible for a building will have a great resource to look at.
The construction companies are also interested in the BIM models and there are so many tools nowadays that can make their life easier and improve the quality of the construction product. One quite common scenario in which a general contractor might want to have the BIM model is to run 4D construction animation sequences. 4D sequences are 3D animations linked to the construction programme. The sequences help rationalize the construction on site. We as Bimmetry have developed a tool called Plan Construction, it is a specialized web platform that helps create a storyboard for their 4D sequence. 4D sequences have different purposes from internal construction variation rationalization to marketing and public dialogue medium. Companies start to make more often also 5D sequences where the animation is not only linked to the programme, but also to the financials. And this is a moment where the cost estimation professionals might get involved as well – To test various construction sequence scenarios and their influence on the budget.

Contactors often do scan to BIM, which is a 3D scanning of a site or a building to produce accurate as-built drawings or to study existing site or construction. Developers on the other hand might want to use the BIM models for space management and tender management. There are a few tools that are specialized for the developer’s portfolio asset management, which are different to the FM tools. But let`s see now how the BIM models are useful for the consultants. Design consultants use BIM to produce 2D documentation and 3D visualizations. You can use the BIM models to make AR and VR walkthrough the models. As we live in three dimensional space, the 3D representation helps us a lot to visualize the design before building it. It also helps us to make clash detection. Here is the moment to mention that as we have multiple consultants on a construction project, so we have multiple models. We usually have architectural firm producing the architectural model, structural engineer modelling the structure, MEP consultants doing the services models. All these models get linked into a single file and by visual digital inspection of the models, we can easily see any clashes that are happening. We can also run automated clash detection and run regular design meetings and report the status of the clashes.

We already mentioned that you could get involved in animated construction simulation including the cost – 5D sequencing. You can also get the models, extract the quantities, and speed up your work greatly. For example, Cubicost can help you do that. All you need to do is insert the Revit model into Cubicost and you have all the quantities structured and you can further add cost to it. The great thing about Cubicost is that it will not only extract the quantities, but it will make automated deductions, which the BIM authoring tools don`t always do. So, if you have a window for example, the volume will be automatically deducted from the wall mass. Cubicost will also automatically generate the quantities for your structural components’ reinforcement and formwork. You basically need 1 minute to import the model and 50% of your cost estimation job is done.

The other great feature of Cubicost is that it will notify you in case you have overlapping geometries, which happens quite often with the BIM design models. But what happens if you don`t have a BIM model and you only have 2D drawings. You can still automate your work greatly using a tool such as Cubicost. You can basically select the outlines of the components such as columns, beams, walls and you can generate a 3D cost model based on the drawing lines and schedules. This is a lot quicker than if you would do this manually. Cubicost is much easier tool to learn compared to the sophisticated design BIM authoring tools, it is designed for QS and cost estimation professionals. Last, but not least you can automatically estimate complex curved geometry like ramps and sloped walls including the reo and the formwork and generate in 3D all the finishings from the architectural schedules. So everything you would base your cost on is an actual 3D geometry and you can visualize all the deductions in 3D. And finally if you are QS and cost estimation professional you could use BIM models just to cross-check your manually generated estimates compared to the automatically extracted ones from the BIM models. It is always good to double check quantities and estimations.

Often people don`t make a difference between a 3D modelling software and BIM authoring tool. For example, BIM authoring tool is Revit, Archicad and Vectorworks. They produce 3D geometry, but every object is recognized by the program as a different CATEGORY with certain properties. For example, a column is a structural component, it has material, profile, cost and so on. The 3D modelling software as Sketch Up and Rhino also generate 3D geometry, but it doesn`t have the meta-data that the BIM models usually have. There are plug-ins and workarounds to turn 3D geometry to BIM model, but essentially this is the major difference. Revit produces 3D geometry and meta data information, while 3D studio max usually is used when we only need 3D representation without the additional information. This is good to be remembered as if you hear that certain model was created in Rhino, then you might not have the data you need from this model, you can reference the 3D geometry, but you might not be able to extract the quantities that you would usually be able to extract from Revit.

Let’s discuss some of the most common problems you might have when you use external BIM models. As with the example with Rhino, you might have complex organic geometry such as stadium canopy that has been modelled in Rhino and imported into the Revit model. In that case your quantities might not come up as you would expect them. Structure might not be detected as well as the other pieces. Using Cubicost you can still use this geometry as a reference to recreate the model as a 3D cost model. This is a quite common scenario – to have certain object not modelled in the correct category. For example, stairs might be modelled just as generic mass model, and of course this won`t be picked up in the quantities schedule as stairs.

As we saw in the Revit interface video, often we have 2D lines instead of actual 3D objects, but it still looks ok for the drawings, the problem comes in the scheduling, you won`t get the quantities for objects that are drawn with 2D lines only. There might be some naming/ type mistakes in the model. Let`s say two identical types of windows might be named differently. You might also have duplicating geometries. Cubicost might help you fix this, but it is a common issue in BIM modelling.

There are some general recommendations to be followed

As the objects to be modelled in the right categories. And stairs to be modelled separate from the railings to get them scheduled correctly in Cubicost. Ramps to be modelled as ramps instead of sloped mass for example and set the structural components as structural.

Well, one thing is in case you are involved early in the design process to mention that the BIM models will be used for QS. And set some requirements to be included in the BIM execution plan, for which we will talk in the next session.

You can of course also review the models. You can open them in Revit directly or in Cubicost, which is way easier for QS professionals to learn and see where you might have some inaccuracies. This kind of issues happen often, but on the other hand they are a very small percentage of the modelled geometry, so it is still worth to take the models and get the most of them.

To get a general quick check you can choose a portion of the building take some estimates automatically and manually and see if the results are similar, this will quickly point you to some conclusion about the quality of the BIM model.

On most projects, we have a BIM Lead/ BIM manager who can be on the client-side, construction side, or consultant side depending on the contract. Usually, this is the person responsible for the BIM execution plan, who defines the future use of the models. If you have special requirements for the models, this is the person to talk to. Also, most consultants have their own BIM office leaders and project dedicated BIM project managers and coordinators. The document controller is the one to make sure the BIM models and documentation is correctly uploaded on platforms such as Aconex or Procore.