Construction errors stem from the design - how much should we care?

Anonymous case study. We fixed errors in a BIM model and compared the impact pre-construction errors would have on the project's cost and schedule.
CAMDEN, U.K. - Jan. 29, 2019 - PRLog -- In a major construction project, we looked at the impact of ignoring seemingly minor errors in BIM design at the planning stage. Many contractors we work with suggest that getting BIM design right at such a detailed level is unimportant on the overall project.

We set out to prove that certain errors in a BIM model can lead to major problems. By getting it right from the start, you can increase the likelihood of achieving your project on time and on budget.

BIM Model Example

The BIM model we chose to examine is one we come across frequently at Kreo: large-scale type A1 (retail) buildings.

We took just one section of the model and chose one specific type of error to fix: the analytical model. In the original model, we found 1,720 analytical model errors. Kreo's machine learning was able to fix around 75% of the errors automatically, bringing the number of errors down to 385.

Analytical Model

When Kreo's AI did the error checking, identified both critical and non-critical to fix. These did not affect the future building's constructability. The errors we discuss in this blog are categorised under the analytical model and are critical to the successful building of the project.

Where two physical elements connect, the analytical representation of the element must have a common node. See the diagram of the error here:

The construction error is where the beams connect. If there is no connection between the beams, they will not hold up the building. This kind of connection is repeated throughout the entire building so the construction error would be multiplied several times.

Direct impact of pre-construction errors

We got Kreo to fix the errors in the analytical model. Then we were able to compare the two versions: one model with errors and one without. We looked at the impact that the analytical model errors would have on:

• Quantity takeoff
• Resources

For quantity takeoff, we compared the masses of the metal structure and concrete in the two versions. The cost difference between quantity takeoff of the original vs the fixed version was minimal (around 1.9%).

When looking at resources, however, there was a different story. The project duration increased from 245 to 290 days once we fixed the error. That's an increase of 15.5% in the project duration that would have been missed.

Knock on effects

Errors in the analytical model are common and can easily go ignored. This lack of attention to detail causes many of the AEC industry's problems. By ignoring errors like this at such an early stage, the project stakeholders ignore the effects on the indirect costs in the long term. An increased project duration increase can result in the need to extend renting periods on roads, temporary accommodation, lease of land…

In a 4D BIM simulation, you can instantly see why a seemingly minor set of errors would cause chaos if left in the plan. The cost and schedule are not the only metrics to be affected. There's also the construction sequence. We took two screenshots of the 4D simulation of the build with and without the error:

You can see the model before and after being fixed. When you realise it would be physically impossible to build your model, it becomes harder to say the errors can be ignored.

Why is it so hard to find and fix pre-construction errors?

Most AEC professionals will read this and agree that it would be ideal to get the pre-construction cost and budget right from the start. Most AEC professionals know how to find and fix these errors. So what stops them? Usually, it's time.

Companies have so little time to bid on projects. According to our research (, around 4 weeks is a normal amount of time given to complete a bid. There are three main reasons that companies struggle to get the bid done in time:

1)     Lack of understanding about how to use BIM, leading to unnecessary delays and mistakes

2)     Lack of collaboration in the AEC industry, meaning getting information from various sources without standardisation

3)     Software designed to speed up people's jobs only helps one or two of the groups involved in the bid, contributing to lack of collaboration (and the vicious cycle continues)

The other factor stopping companies getting this right is money. When companies bid on for a project, they often have to bid low to win the project, even if that means ignoring the details. Clients are also prone to overlooking bids that might be more accurate in favour of the lower bid. This race to the bottom only works for so long, as we saw in the infamous case of Carillion ( this time last year.

What's the solution?

We at Kreo believe that the pre-construction phase of the construction project is key to getting projects to run on time and on budget. CEOs need to start taking pre-construction more seriously. They must give their employees all the tools, education and time needed to achieve better results.

AEC professionals need to start working smarter – not harder. If companies used modern technology to speed up their pre-construction planning, they would be able to bid on more projects. Ultimately, they would be able to evaluate whether a project was realistic before even bothering to bid on it.

Technology is finally ready to increase AEC professionals' productivity. It will make pre-construction errors a thing of the past.

Julia Valentine
Head of Marketing, Kreo
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Location:Camden - London, Greater - England
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