Observations on Architects CAD Data and Professional Liability

(Adapted from an original text by Chris Dennehy and published with his permission.)

These thoughts are concerned with the long term archiving of drawings and other documents and are not about the day to day backing up of computer documentation though some bits may be relevant to daily back up. They also raise the specter of unauthorized amendments by other parties.

Documents may be required for a number of reasons, firstly a client might just possibly come back for a second round or secondly, one might be unfortunate enough to have to mount a legal defense, appraising things from the latter viewpoint should take care of the first instance.

In either situation you require drawings and possibly correspondence and relevant product documentation. With the advent of computer technology this is the first time since written records were kept, in whatever form, that we have been unable to see the record with the naked eye, obviously it is therefore necessary to maintain some method of retrieving this information in a form we can read, with the way technology is changing this is very difficult indeed.
It should be noted that insurance companies tend to sue everybody and anybody remotely connected with you and/or the project in question in the hopes of striking the jackpot and getting somebody other than themselves to pay up.

The printed image:

In days of old we ended up with just one negative on tracing paper, suitably scratched out and amended all over with (hopefully) revision notes that actually meant something capable of being correctly interpreted in years to come by somebody unfamiliar with the job.

If we were lucky it was actually on tracing paper and not on one of those modern long life films that discolored and shattered into fragments after a few years.
This single negative presented storage problems, placing them in rolls is/was a sure fire way of making them more or less unprintable after a few years, though some offices still do it. The one thing it did have was clear evidence of amendment which was generally acceptable as normal practice for the time, it was/is possible for experts to say whether the amendment was recent or dated back to the time of origin of the drawing if things become really difficult.

To mount a successful defense to-day, it may be necessary to show the complete history of the job.

The current practice of maintaining a copy on disk of each revised drawing with it’s revision notes as it is issued has a lot going for it as it provides a record in chronological order of each change made. The disk space required is, of course, enormous as it the storage space required for storing the negative if retained. Keeping a copy of revisions as they are made is relatively simple under most Architectural CAD programs.
Changes in printing techniques are now beginning to, or will, cause problems perhaps in the not very distant future. The dyeline technique is now almost gone except for the smaller office which clings onto obsolete machinery. The A0 photocopier machine is costly, has a large footprint and heavy maintenance costs, the quality of its prints is generally disliked and it is gradually being replaced by machines that print directly from the HDD (and which can also scan in drawings but see note below). When it comes to upgrading their plotters, many offices which do not have high printing volumes are now replacing their plotters of various sizes with the newer types which can, in theory at any rate, produce a plot in 45 seconds, and have dispensed altogether with large format printing machines.

The change from pen plotters to ink jets has itself made changes in reproduction techniques, if you take a file designed for pen plotting and now plot it on an ink jet without any amendments the chances are that it will look very different from the original. When plotting with pens, lines were heavier because of problems with the pens themselves and it was also common practice to use a colored ink pen for shaded areas as this printed on the dyeline machine in different weights of gray adding depth to the drawing.

All this means that the chances of reproducing something in a few years time that looks exactly like the paper original the client has tucked away someplace and handed to his lawyer is getting more and more remote; just think how much mileage a good lawyer is going to make out of two documents claimed to be identical but which look different. A simple font change is going to give them a field day.

If it is decided to dispose of drawings to reduce storage requirements, I suggest that door schedules and any other documentation relating to fire precautions are retained. In a recent fire in a domestic situation, several people were killed in circumstances where this should not have been the case, investigations showed that the owner/occupiers had replaced fire doors with “nice glazed doors”.

As the legal system seems to be light years behind the computer industry and it’s practices, it will be interesting to see what happens when somebody arrives into court waving a CD and saying its all here judge but we can’t open it.

The problem is further exacerbated by :-


Programs that come with a hardware lock/key/dongle whatever you wish to call it, present particular problems in relation to backwards compatibility and the possibility of having to resurrect long dead drawings, the legal considerations of this does not appear to be fully considered by program vendors.

e-mailing drawings etc.,

E-mailing your drawings/documents to others presents certain problems of authenticity, how do you prove that the drawing you sent was changed by the other party and the defects that arose were due to that change. On the other hand e-mailing drawings to other members of the design team does have certain advantages, generally they either overlay their own information on top of yours (services engineers) or axe out anything not of interest to them (structural engineers), this means that there is at least some semblance of your drawing floating around which can be resurrected if your system fails.
I have no idea how this could be made to work, but to obtain protection from defects caused by unauthorized changes to drawings, some form of data lock is going to have to be found that allows others to add their information to your drawings while at the same time preventing your drawings from being amended. Such a lock would have to extend to the layer structure, layers turned on/off could cause as much trouble as amended drawings. Apart from interchange between offices all using the same CAD system, most drawings are either exchanged using .dwg or .dxf formats. Therefore, such a system would have to extend into these realms. To reduce the risk as much as possible, I suggest that drawings issued electronically should be cut down as much as possible and only incorporate such detail as is required by the recipient.

Is data interference far fetched? I don’t think so. As sure as God made little apples, somebody somewhere is going to find themselves on the wrong end of a defects case and decide that the best way out of it is to alter the other persons drawings and shift the blame.

Drawing issue sheets are all very well but they are unlikely to provide a definitive proof of the issue of drawing. Someplace, sometime, a drawing has got out without one and that’s the one that’s going to be quoted at you.

One reaction is likely to be that only printed copies should be issued, in the electronic age however, this would represent a retrograde step and is unlikely to prove acceptable to the construction and engineering industries.

Registered mail:

Can be a help in proving the date of a document, a simple procedure is to enclose documents that might be contentious in a registered letter and mail them to yourself where they are retained in a secure vault (doubtless everybody has one), unopened until you are in court, you are then relying on the post office to maintain their proof of delivery dockets and to prove delivery on a specific date.

Disk life:

It is generally recognized that a magnetic disk has a maximum life of around 5 years but as manufacturers only give around 3 years guarantee with their product then I think it unwise to rely on a drive for more than this period, I suspect that removable drives have a much shorter life span than their guarantee because of the abuse they suffer and are, in my opinion, not really suitable for long term storage.

Tape Drives

I don’t think that tape drives can be relied on for much more than short term storage, most manufacturer’s only give a 2 year guarantee on the unit, they also rely on the software operating systems and programs being maintained in use and/or the retention of old machines in working order that can be relied on to operate them.

There is also the problem of wear with drives which deposit data on a tape using helical based technology, the screw can apparently become misaligned over time and trying to open data placed on a tape say a couple of years  previously may not be possible.

As tape drives change all the time (continuous improvement is the manufacturer’s term for finding how to take another shortcut and make it cheaper), trying to open an old tape on a new drive could be interesting.

The life of a tape should also be taken with a grain of salt, they might last the number of years specified, but will you still have the operating system and equipment to run them, then of course there’s Murphy’s Law, the break in the tape will contain the data you want.

This looks like the best bet at the moment as every machine has a CD drive but they also rely on the software operating systems and programs being maintained in use to retrieve the data. New types of CD are supposed to arrive next year with greater capacities but I don’t know if you can use them in the same drives or if they can be re-written.

[[[Placing pdf files on CD’s may not be a bad idea. Kodak claims a 200 year shelf life! Acrobat reader could be on every CD to help ensure future readability.]]]
DVD or Blu-ray

I know this has tremendous potential but think I’d wait and see how this one’s going before I plunged.

Manufacturer’s brochures:

Manufacturer’s change their specifications from time to time. A 20 year old brochure showed that a defendant had met the manufacturer’s specifications at the time, thus relieving him of responsibility for the fault which developed. The standards were well below those currently in operation. The opposing lawyers were rather disappointed.

Clients brief:

A person was doing house inspections for a lending company. A fault developed and a house purchaser sued. The company by whom he was retained stepped back and he was not in a good position. Fortunately for him, he unearthed an old written company instruction sheet listing what was to be inspected. He had followed the instructions to the letter and was saved, so keep the client’s brief.


One further point, occasionally everybody has to report on the condition of a building. If you notice something that needs to be repaired or replaced, it is not enough to say so. You must also say when it is to be repaired/replaced. When inspecting a pumping station a consultant recommended that a pipe carrying chlorine be replaced. The client noted the report but took no action. The pipe failed and a workman received serious injuries. The judge ruled that the consultant was 80% responsible because he had not stated when it should be replaced. To be on the safe side, include a carefully worded definition of all the times you give such as “immediately means – on receipt of this document”. Bear in mind however that the period given to repair/replace an item should allow, where necessary, for its manufacture and/or delivery, therefore include a note to that effect in your report when calculating the time for an action to be taken, otherwise you could be faulted for being unreasonable. Send the report as fast as you can by registered/recorded delivery or some other approved method where a record of delivery is obtained and can be verified, maybe years later. Very careful thought has to be given to the method of delivery, it has to be verifiable, somebody is going to have to sign for it, at the same time it has to be as fast as possible so you can’t be faulted for delay and the opportunity for somebody to refuse a report and leave you unable to deliver it has to be removed.

There are a lot more whereas’s, heretofore’s and whatsoever’s than mentioned above that should be included in a report and the definitions of times and method’s of delivery of a report, particularly one that could be contentious, is a lot more complex than indicated in the foregoing paragraph which barely indicates the tip of the iceberg – take care and keep several copies.


If the maintenance of an archive that is fully up to date is essential then:
Keep a record of the dates on which operating systems were introduced and upgraded.

Do the same for all changes in software programs and hardware reproduction and storage systems.

Keep a hard paper copy of every document relating to a project in a place that is safe from water, fire, vandalism, general decay and any other risk you can think of.

Upgrade every computer generated document each time you change operating systems and programs on to the most robust storage medium available at the time.

Keep duplicate copies of everything in separate locations and I don’t mean each side of the desk.

Change your hard drives on a regular basis.

Review your long term storage media and retrieval systems on a regular basis and update when necessary.

Maintain an insurance policy that covers electronic data loss. This should also include a lump sum payment for somebody to redraw lost drawings. Remember the computer industry says that a firm experiencing data loss has a good chance of going out of business within 6 months.
It is perfectly obvious that most of this is not going to happen unless you want to give up architecture and become an archivist, so whatever you do, it is going to be important to show that you have taken all reasonable precautions. Make sure your definition of reasonable prevails.


For those of you who haven’t tried it, scanning hand drawn drawings into CAD systems may not be as attractive as it first sounds unless they are to be stored and printed without amendment. Hand drawing is not accurate in computer terms and although lines on the drawing may look vertical/horizontal to our eyes they are probably wavy to the computer, by the time you have everything straightened out, including hand drawn text, removed coffee stains and the like, it may well be quicker and easier to redraw it directly into the program.

Now the traditional disclaimer:

Anyone who relies on the above personal opinions/thoughts and bases their approach to document archiving/storage and general and data security on them without doing their own research, taking appropriate technical and legal advice and checking things out for themselves is a raving lunatic.


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