A lack of trust in drawings and 3D

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Regular AEC Magazine contributor, Rob Jamieson, shares his frustrations as a string of delays to his house extension could have been avoided with good use of drawings and 3D models.

It can get cold in winter when your house is missing an external wall.

Last year my wife and I bought a new house and decided to have an extension built. I was aware that nothing moves quickly in the building industry — the planning process, fixing neighbours’ objections, getting reference and hiring builders took a whole year in itself — but what has amazed me is how drawings and designs can be so different to how they are interpreted on site.

As I was a building virgin, so to speak, I hired an architect to manage the process. The drawings were completed in 2D with some 3D sketches. It was the first time I’d been directly involved in building work and while it’s not a big project I’ve been living with it every day so I’m very close to the process. And with my experience in CAD I couldn’t help but think where technology could have sped things up.

Drawing, what drawing?

A key stage in the construction was the insertion of steels to support the back of the house and the new extension. These took time to come because the builder would not order them until the bricks had been knocked out and he could measure the size.

I questioned him about this and asked ‘why not take the measurements from the drawings?’

Apparently, years of experience had taught him to never trust drawings from architects. He then proceeded to tell me about a handful of previous jobs where he had encountered problems as a direct result of putting his trust in drawings. Duly the steel was delivered and lifted into position. The height was then measured and the vertical steels ordered.

I understand that it’s an old house so nothing is guaranteed but I became frustrated with this highly serial process. Each previous bit of the build needed to be completed before the next one could start. While I understand that this can lead to better build quality it also means I’ve been eating microwave meals for a lot longer than anticipated.

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A mistrust of drawings can also lead to important details being missed. Our builder started to construct the wall between us and our neighbours too far away from the boundary line. When I questioned this the builder said you needed room to put a rainwater gutter on the roof that and it can’t overhang the neighbour’s property. While this is true in most builds, if he had paid proper attention to the drawing he would have seen that there was not a gutter on the neighbour’s side as the rainwater went down a central channel. With a bit of re-jigging we gained another 10cm back along the wall. I’m now totally convinced that you need a site manager.

Digital dreams

A CEO of Autodesk once said that keeping the design data digital would make them more money longer. Beyond the financial benefits to Autodesk’s shareholders, it’s been widely reported that using 3D can also help identify potential problems.

During the construction process our builder realised that a trough for heating near the glass doors would impact the height of the storage area. Thankfully, because of his experience he noticed this would be a problem before he created the wood shoring for the concrete. My suggestion of looking at the design on a laptop and the 3D drawings fell on deaf ears, and while it would have shown the problem clearly, the builder would only look at the 2D drawings.3D also has the potential to lead to better designs. Earlier on in the construction process, we had found the groundwork was harder than anticipated with more concrete slabs under the top slab. Nine skips later we had a big hole which was filled with new concrete to the new size. Once this was done we realised that the under store could be increased to twice the size without any real additional cost. Why did we not see this before? All of the 2D drawings and 3D sketches were above ground. 3D and the use of volume calculations would have made a massive difference here. Everybody wants more storage.

Of course, keeping things digital 3D on site has its problems. Most laptops wouldn’t survive long in mud, being balanced precariously on a wall or acting as a tea coaster (tea is very important to builders). But paper drawings have their problems too. The latest drawing revision is often the one which is still readable and not necessary the latest issue from the architect!

I don’t think the issues I’ve encountered in the last few months are specifically down to our builders (I still think the builders are very good, well the building inspector does). In the construction industry in general there is an underlying mistrust of architect drawings — 2D or 3D. Paper and prints are still going to be the way builders get their information most of the time whether it’s a small extension or a major building project.

As I write this we have just found out that there is a six-week lead-time on the rear doors. The builder wouldn’t order them until the wall was built. And, most frustratingly of all, they are exactly the same size as the ones on the drawing. I’m hoping for a warm summer as plastic sheeting is not a good insulator!

Rob Jamieson is a marketing manager at AMD. This article is his own opinion and may not represent AMD’s positions, strategies or opinions.

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