General CAD tips

Calum and Carl have worked as Technicians specialising in the production of construction detail and tender information on major construction projects for over 40 years (combined experience). During this time, they have identified a number rules that will help speed up the production and accuracy of AutoCAD drafting. Carl and Calum pioneered the development of an 'Elemental Approach' to AutoCAD (from as early as 1989), and this methodology along with the basic rules of CAD operation is a significant factor in terms of OGH’s ability to produce highly accurate information in a timely manner.

Some of OGH's basic rules on CAD use:-

Don’t:-

• Don’t use Auto Snap - the F3 button is one of the most dangerous on the key board if you are working at speed - contrary to popular belief, in addition to being unsafe in terms of accuracy, it slows down production (AutoCAD can snap to lines that have zero length! - and they are more common than you think!) - we are currently trying to source a keyboard that does not have this button!

• Don't use desktop tools - they reduce your speed by as much as 50% - learn to work off the key board [using our comprehensive list of single and double keystoke shortcuts], they also occupy valuable [and expensive] areas of the screen better reserved for drawing on;

• Resist the use of drop down menu's wherever possible - it is 2 or 3 times quicker to enter the appropriate keyboard command [by moving the mouse away from the work area you are also ‘taking your eye off the ball’];

• Don't snap to end points unless totally unavoidable - use 'Offset', 'Extend', 'Copy' and 'Fillet' to create objects (assuming the lines you are working with have been created properly in the first place?) (AutoCAD can snap to lines that have zero length! - and they are more common than you think!);

• Don't work on a new drawing or new revision until it has been 'Saved-as';

• Don’t use the company initials as a basis for layer identification - the letter A will suffice and is quicker to type in - everyone will know that it is the architect's layer and layers beginning 'A' happen to fall near the top of the list (below numbers) so our architectural layers are very easy to find! 

Do:-

• Remove all desktop tools - this opens up the screen to show more of what you are working on, and these ‘tools’ only slow you down;

• Set the Auto-save so that your work is automatically saved every 10 minutes to your own hard drive - make sure you direct it to a purposely-created folder. In our experience, the auto save function is totaly reliable (if it is set up correctly!) [note that the increment save should be set to zero!];

• Complete your timesheet in detail - those that instruct you to make changes to your drawings often have very short memories!

• Save your work (Qsave) often, but most importantly before you leave your work station or answer the telephone - retrieving the Auto-save file takes time, and you may lose a few minutes work if the system crashes, so make 'Qsave' one of your habits. Always save your drawing before printing, applying hatch patterns or attaching xref’s – these operations commonly precede a machine 'crash';

• When creating the layer names, use capital letters – this saves time, and the 'Caps Lock' key on your key board will last as long as the rest of the keyboard!

• Keep check of your layer discipline - make sure you have the correct layer as current at all times unless copying a previous feature;

• Insert xref's on layer '0' or a dedicated and aptly named layer such as 'A0xref';

• When you start work, create the paper space sheet and set up the view ports, layer switching, etc. within the first 30 minutes! - those not so conversant with CAD may want to see how you are progressing the drawing - a heap of lines in model space may not impress them after a couple of days have passed! [Maintaining an A3 desktop reference set of drawings will be found useful to all].

• Create architectural layers by using the letter 'A' followed by the level number (if drawing plans); followed by a short and clear description e.g. ext walls; int walls; windows; doors; insulation; lintels; cav closer; timber; plank; PB; mechanical; mortar etc... Avoid using CI/SfB number referencing in the layer discipline unless specifically requested by the Client – it is unnecessary;

• Before creating blocks, ensure all lines and components are in layer 0. Before inserting a block, ensure the current layer is the layer you wish to control the block by, e.g. before inserting a door, check layer ‘A0?? ??? DOORS’ is current;

• Avoid the use of ‘true type’ fonts – they can slow processing down on heavy detailing work unless you use a very good graphics card. True type fonts like ‘Arial’ are best used for presentation drawings only, but even then unexpected results can occur when printing on certain plotters; Also, check your spelling carefully - we all make genuine spelling mistakes from time-to-time but its worth a quick go with the systems 'spell checker' before you issue the drawing. Also, spell 'lintel' and 'mortise' correctly - you would be astonished how many archityectural words are spelt inncorrectly! - buy a good dictionary.

• Create only A1 drawing sizes and make the font readable at A3 so that a reduced scale set can be useful if printed (unless the client's QA system stipulates a smaller font). Keep each drawing as a seperate file;

• If required by the client, use only the NBS section reference (short reference) for materials – e.g. ‘Facing brickwork (NBS F10) to be…….’ etc. - but avoid if possible - The QS wont even read them!.

• When amending a drawing from a 'marked up print', always cross off the changes with a highlighter pen as you finish each of the changes. 

The Elemental Approach:-

OGH have developed an elemental approach to the production of construction details. The approach is largely applied to GA sections, horizontal and vertical details. Instead of creating the GA sections with lines, sections are formed from components in the form of closed poly lines or grouped elements. By creating GA sections in this way, accuracy and clarity of detail is maintained, and the finished GA’s form a solid basis for the production of the larger scaled vertical and horizontal details, and ammendment/change is made easy. 

With the exception of grid lines, floor level lines and occasionally hidden lines or other lines of reference, every element within the section of the structure is produced as a closed poly line. To enhance further, complex elements are grouped so that they can be stretched, manipulated and selected as a whole - grouping objects is dangerous in the hands of a novice, so unless you know exactly what you are doing, don't group!

Once the first section drawing on a project has been created, it can be readily copied in whole or in part to form the basis of further sections. Naturally, the first section in a series needs to be very accurately, and thoughtfully produced. The additional time spent in production of the first section is more than justified, as the production time of further sections is reduced considerably and set-out and alignment is accurately maintained with little effort.

By creating elements/components in groups or by using closed poly lines, single objects or groups of objects can be selected, copied, deleted or added with ease, and the timely process of re-creating features by trimming or stretching individual lines is almost largely bypassed. In addition to copying the drawn information, construction annotation can also be repeated, reviewed, modified, added or omitted. Selection of the correct section on which to commence the detailed work takes experience, but masonry coursing is often a significant factor, so the appropriate first section is likely to be through the highest vertical façade through the masonry elements followed by the same section but cutting through any fenestrations or significant features.

Vertical and Horizontal detailing approach to construction package production:-

By applying a vertical and horizontal detailing approach, the number of drawings required can be considerably reduced. More traditionally, buildings are detailed out in isolated packages – e.g. stairs are separately drawn and detailed, window details are isolated and presented separately, roof details are all placed on separate drawings etc. By doing this, not only are additional drawings unnecessarily generated, but a good deal of repeat information is generated and this makes revision a complicated task, thereby increasing the likelihood of errors or conflicting information appearing in the drawing set.

Almost all details/features can be picked up in a comprehensive vertical and horizontal detail package, and the likelihood of overlooking specific details is less likely to occur if a systematic and logical approach is adopted to producing the section details – e.g. left to right, level 1 and upwards, external through to internal. A vertical and horizontal approach is likely to pick up over 90% of the detailed information required for quantification and construction purposes. Any remaining details can be generated separately (usually) quite readily by reference to the vertical and horizontal detail set. The correct application of this approach will typically reduce a construction package down by as much as 35% in terms of drawing numbers, improve accuracy and consistency of information, and reduce overall production time considerably. Naturally, the Client will decide whether the the spare money exists to produce the unnecessary repeat information - packaged information can be efficiently compiled from the completed information if required.