Point Cloud Model Eliminates Waste During Complex Construction

One of the most challenging builds ever seen on Grand Designs comes in on time and on budget after 3d laser scanning confirms accuracy of just-built items prior to ordering prefabricated components.

Construction is risky. Thats why the final bill is often 30% higher than anticipated. Errors lead to rework which increases waste, elongates the schedule, and increases the cost. It also raises stress levels for all concerned, especially when the budget is fixed. So how do we reverse the trend? How do we bring projects in on schedule, and on budget?

We could simply change expectations from the start; for a one-year build we could schedule it over two years, and for a 1million job, we could plan to only spend 600k from the outset. Chances are the project will come in early and under budget; a sure sign of success, right? Well not really. The project will underwhelm because the value just wont be there. The alternative is to tighten up on everything and to better predict when and why things might go wrong before they do so that we can alter course and avoid them.

An upfront investment in design (with talented designers) will always pay dividends in terms of the quality and usefulness of the end-product. Similarly, investing in a conditions survey of the existing site and surroundings will pay dividends for design and construction strategy and predictability. This isnt rocket science and no one will disagree or think me a genius for writing it. The truth is, the more information we have, the better placed we are to make good decisions.

So why then do we generally stop surveying before we start building? I dont mean checking levels of course that continues I mean checking that whats been built is what was designed. Again visually we do that, but accurately? Hmmm, not always. Perhaps because we never needed to. With skilled trades working on site, almost any new component can be made to fit the existing; if working with wood you just keep on measuring and trimming. But if working with prefabricated components (manufactured off-site and shipped in) like steel or concrete the game changes significantly.

Get those wrong and the build stops. Why then do we design and detail prefabricated components as a parallel process to the layout and construction of less precise wet trades on site? Surely if one ends up even slightly different from its design which is a common occurrence the project is delayed and the cost escalates. Construction projects are in effect enormous and sometimes unpredictable change-management initiatives. We know this all too well and yet still we continue to push on without taking time out to accurately check the progress as we go.

I say all but there are some who refuse to leave change to happen without trying everything within their power to manage it. And those folks tend to achieve far better results. Take a look at Helen Seymour-Smith; the architect, project manager, and perhaps most importantly in this case the client for an audacious project in one of the most challenging locations imaginable. Helen and her husband Chris decided to build on the site of a tumbledown barn, precariously perched on a hillside in the Cotswolds an area of outstanding natural beauty.

Initially the planning authorities said no way! but the couple pulled a rabbit out of the hat and gained special planning permission to build a house of exemplary architectural merit underground. To make their challenge even harder they set out to build the first accredited passive house (www.passivhaus.org.uk) in England which would require almost no heating or cooling thanks to its incredible levels of insulation and airtightness.

With a fixed budget and no wiggle room the Seymour-Smiths wanted to get the most value out of their investment without risking any overspend. That meant sticking to a sensible schedule and eliminating any waste from errors on site. Easy! you say. Perhaps; except that the design included a veritable mix of prefabrication involving steel frames and precast concrete wall panels and in-situ ground works and wet trades. Thats just the kind of stuff that gives rise to poor fit and finish; which will do nothing for airtightness, the schedule, or the budget.

Helen realized this, so got smart. Theres an old saying in the building game, measure twice, cut once and thats exactly what Helen did when her dream project was showcased for all the world to see on Channel 4s Grand Designs TV show. Keen to eliminate her exposure to risk, Helen turned to 3D laser scanning to accurately measure the size, shape, and location of the formwork and reinforcement. After only 3 seven-minute scans [taken from different positions] using a FARO 3d laser scanner, we had a complete 3D point cloud model of the site. Then using the Pointools plug-in for AutoCAD, Helen combined the accurate 3D point cloud model with her detailed design model inside AutoCAD Architecture to compare the just-built items with the as-designed model.

This was particularly vital for the ply box-slots around the slab edges that the pre-cast concrete wall panels would sit in. Seymour-Smith explained the risks they faced, Had we got this wrong, the concrete wall panels simply wouldnt have fit – and unlike a bit of wood, concrete panels such as these can’t be reshaped on site. The cost of getting it wrong would have been immense. At best, the team would have been forced to cut into the floor slab, compromising its structural integrity and wasting precious time and money. At worst it would have been a case of starting over.

Of course nothing went wrong. The 3D point cloud model confirmed that all was good; the work already done on site was spot on and the concrete pour went ahead as scheduled. The pressure was off, the risk of errors eliminated. The concrete wall panels arrived on site and slotted into place perfectly. But that wasnt the end of it. The airtightness results for PassivHaus status blew them away (if youll excuse the pun). We needed to achieve fewer than 0.6 air changes per hour to meet the PassivHaus standard and we achieved just over 0.2. Thats 3x better than PassivHaus requirements and 50x better than UK Building Regulations enthused Helen.

Oh, and did I mention? The project was completed on time and on budget, their grand design was realised.

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About the Author

Joe Croser

Joe Croser ... has more than 20 years of sales, marketing and product experience in the architecture, engineering and construction (AEC) industries. Joe is the Managing Director of Oundle Group, a business development consultancy that helps technology firms grow. Joe also ‘gives back’ as an Enterprise Programme Mentor at the Prince’s Trust – a charity that helps young people build new lives. Before starting Oundle Group in early 2012, Joe was the Vice President of Products at Pointools – a company he helped grow by more than 70% in just twelve months. Prior to that he was Global Marketing Director with Bentley Systems, Inc. There he provided marketing leadership for more than 75 percent of the company's revenue-generating products and software subscription offerings. During his five-year tenure, Bentley's revenues increased by 60 percent from $300m to $500m. Before joining Bentley in 2005, Croser served as Technology Strategy Director for Parkview International London PLC, a Hong Kong-based property developer. Prior to that he gained valuable project experience working with some of London's best known owner-operators and AEC design firms including the BBC, BAA, Richard Rogers Partnership, Buro Happold and Reid Architecture. Joe studied architecture in Oxford where he gained a Bachelor of Arts degree. Joe Croser Managing Director, OundleGroup www.OundleGroup.com +44 (0)7837 034 080 Follow me on twitter or get connected via LinkedIn     Contact Joe Article List Below