Saturday, 26 January 2019

How Do You Solve a Problem Like Ma Railings?

Have you ever encountered a problem with out-of-control railings in Revit?  OK, so maybe the structure shown above is not a haywire railing, and was meant to be like that, but most Revit users have struggled with trying to model railings as they should be.

How Do You Solve a Problem Like Ma Railings (in Revit)?  *

* with apologies to Richard Rodgers for misappropriating his song title (How Do You Solve a Problem Like Maria? from the Sound of Music, By Rodgers and Hammerstein) - not to be confused with Richard Rogers (no d), the architect who designed many famous buildings, such as the Pompidou Centre in Paris (with Renzo Piano) and the Lloyds Building in London.

Richard Rogers surely did not struggle with trying to model railings in Revit, as those buildings were designed long before the advent of such software.  These days we certainly do struggle with the software - Revit has been around for almost 20 years and it still it does not enable us to model Railings the way we want them (except for the most simple handrail).  There are many problems with the railing tool in Revit, some of which have been documented on this blog - see the list below.  Over the years, we have benefitted from several minor improvements to the railing tool - for which we are very grateful.  However, there is one fundamental problem that has not been resolved - and that is the inability to control the location of individual balusters.

Baluster Placement - a Fundamental Flaw

The railing sample file shows some relatively complex looking examples - but these are just straight runs on the level.  As soon as you try to use them on stairs, things start going wrong with the baluster placement.

This example is done using two alternating balusters - one is just a post, while the other is glass with fixings.  The glass baluster is very good at adjusting the angle of its top and base (if you create the family properly). 
When it comes to spacing, it is pretty hopeless:  you get gaps whenever there is a break in the pattern.
Standard railing with glass balusters
There are some limited controls within the baluster placement type properties, but no single combination of settings will ever work on the whole stair railing.

Spreading the pattern to fit does resolve some issues, sometimes. . . .

Changing the 'Break-Pattern' property to 'Never' can have some weird results

Reverting the pattern to 'Centred' does not fix it either - you may end up with panels across a change in angle, where the panel is not trimmed properly.


There are a number of ways that people get around these problems, but none of them is satisfactory:

1.  You can try using 'Handrail Supports' to represent balusters, but that has at least two problems:
  • Handrail supports do not respond to changes in angle of the stair, so you need to build that in as a user control that has to be manually set every time
  • Handrail supports can be unpinned and then moved (or changed to another type), but the moving process is very tricky - see Moving Handrail Supports
    It is also possible to very easily lose the positions by accidentally resetting the railing.
2.  Model the glass as a continuous rail element, use balusters and/or handrail supports to represent the fixings and vertical joints in the glass.  More on that another time.

3.  Model the railing 'in-place'.  This is a really bad idea as it screws up the subcategories, visibility etc;  And worse still, it does not update when the stair changes

4.  Just model a Top Rail / Handrail (with no balusters), which shows up in plan.  Document the railing in 2D as drafting views or as detail elements on stair sections.  This is a terrible solution (very un-Revit-like), but it can save huge amounts of modelling time - so it is done quite commonly in the industry.  Of course, it can lead to errors on site . . . .

Railing Fixes

If we had the ability to control the baluster placement in much the same way that curtain walls operate, it would help resolve this fundamental flaw in the railing tool;  this would require the ability to include variable width panels too.  Of course there need to be many other minor fixes in addition to that. 

On the Autodesk Revit Roadmap, Railings were flagged as 'fixed', a couple of years ago, on the basis of a number of minor enhancements.  Clearly it is nowhere near being fixed - see this request on 'Revit Ideas'  Railing Overhaul - Resolution of Limitations - from Chris Price (Mr Spot).

Weird Railing Stuff Blogs

Over the last few years I have posted many blog articles on the many weird quirks of using Revit to model Railings.  Some articles just document the inconsistencies and strange behaviour - just so you know what is going on; other articles offer some workarounds and ground-rules that might help you along:

Revit Railing Enhancement Requests

Autodesk  have a 'Revit Ideas' website that allows you to vote for enhancement requests.  I have compiled a list of stair/railing related ideas - please, all of you vote for some of these requests - if you don't vote, Autodesk will continue to consider them as fixed.

Sunday, 13 January 2019

Weird Railing Stuff - part 16 - Rail Hand Clearance Property

Following on from my previous post about Railing Offsets, here is some more detail about the ludicrously inconsistent UI for Handrails and Top Rail offsets in the 'New-style' railings.

Handrail Offsets

Handrails can only be moved laterally within the Handrail Type Properties (not in the railing properties).  This is controlled by a property called 'Hand Clearance'

The Hand Clearance property dictates how far the inside face of the Handrail is offset from the 'Notional Railing Centreline', which is not necessarily where the wall or other railing elements are*.

  • The Handrail family has a ‘Hand Clearance’ property, and projection property (see below)
  • In trying to use a real-world term, Autodesk have muddied the waters and made it totally confusing to work with.  This property is only logical with certain types of railings:
    • one example might be a wall-mounted handrail that has no other linear elements; and even then it only works when the Railing 'Offset from Path' property is set to zero.
    • If the railing has balusters and posts, with a Handrail mounted on those, the ‘Hand Clearance’ property does not take account of the baluster/post width, so you'd need to add in half that width yourself.

Once the Hand Clearance property is set in the Handrail family, you have to go back to the Railing family to see the effect it has on the whole railing, where the calculated Lateral Offset is displayed (not shown in the Handrail properties).

The Lateral Offsets are calculated by the system, depending on the Handrail type properties.  Typically this should be:
  • Hand Clearance + (Profile Width / 2)    - in this case  40 + 30/2 = 55mm.  
  • The Lateral Offset represents the centreline of the Handrail relative to the notional centreline of the whole railing (which is itself moved around by the 'Offset from Path' property).
  • If you want a centred Handrail, you need to make its hand clearance property minus half the profile width
Projection Property
  • There is another calculated property that is displayed here: 
    'Projection', which is calculated as (Hand Clearance + Profile Width)
    It is again greyed out, and updates immediately after any changes to the profile width or Hand Clearance.
  • I cannot see the logic of having this property displayed here, while the Lateral Offset is not.

Changing Properties

The knock on effects of any changes you make is again, a little confusing:
  • If you change the profile type, and hence its width then the 'Hand Clearance' is likely to change.  What Revit is trying to do is maintain the 'Lateral Offset' value, and hence the centreline location of the Handrail.
  • This may be logical to the software programmers, but not to designers, who would want to maintain the Hand Clearance when the profile width changes.  
  • The end result is that you need to pay careful attention, and manually change the Hand Clearance yourself after every profile change.
Once you have made any changes to the Handrail Type properties, then click OK, it returns to the Railing Type properties (if that is where you started from).  There is a display bug here:
  • The Lateral Offset does not appear to be recalculated (although it is).
  • To cause a display refresh, you need to change the value of the 'Position' to something else, and then back again.
  • Alternatively you could close the Type properties and reopen.

Wall-Mounted Handrails

In the case of Wall-Mounted Handrails, where there are no Top Rails or Balusters, the settings need to be somewhat different - and this is about the only situation where the term 'Hand Clearance' makes any sense.

The Railing Instance property 'Offset from Path' needs to be set to zero.  It is very frustrating that this is not a Type property, or at least have a default value stored within the Type properties - as you need to remember to set it to zero every single time you place a railing of this type.

The Handrail Type properties should be set with the actual Hand Clearance that you want - say 40 or 50mm.

Make sure that you choose the correct profile size first, as Revit will alter the Hand Clearance if you change the profile.

The Railing Lateral Offset property will be set automatically.

Top Rail Offsets

  • The Top Rail family also has a ‘Hand Clearance’ property, and projection property.
  • This is confusing - the Top Rail is meant to be there to support other railing elements, although it may double as a handrail. Whether it serves as a handrail or not, it would typically be centred with balusters etc on the 'Notional Railing Centreline', which is what the Hand Clearance value is measured from. 
  • Just to make it doubly confusing, the Top Rail offset is inconsistent with Handrail offsets:  a positive Hand Clearance value moves the Top Rail outside the stair in plan (Handrail moves inside stair).
  • Although the calculation for Lateral Offset is the same, it moves the opposite way:
    • (Hand Clearance + Profile Width / 2) - in this case  -25 + 50/2 = 0mm
  • If you want a centred Top Rail, you need to make its Hand Clearance property minus half the profile width of the Top Rail.

If you set the Hand Clearance to zero, you would get a Top Rail offset by half its width from all the balusters (unless they also had offsets . . .)

Here is  more information on the inconsistency between Top Rail and Handrail Terminology

Monday, 7 January 2019

Weird Railing Stuff - part 15 - Railing Lateral Offsets

I started out writing about the 'Handrail Hand Clearance' property of Railings in Revit - then I realised that it would involve analysing all of the related lateral offset properties associated with Railings and each different component.  It turns out to be a real "dog's breakfast", with at least six different ways to offset railing components, with minimal consistency between them all.  So I decided to document that first before looking at how it all affects 'Hand Clearance'.
Colour coded railing sub-elements
The above view of a railing is colour coded to help distinguish each sub-element; it is set at an oblique angle so that offsets are clear to see in the following examples with exaggerated offsets of 500mm.

A Dog's Breakfast

Railing Sketch line.

When a railing is placed automatically on a stair, it has a sketch line, that is typically on the edge of the run/landing.  All railing lateral offsets relate back to this sketch line location.

1.  Offset From Path

This is an instance property, which is applied to the whole railing and all its sub-elements.  
It represents a notional centreline of the railing, offset laterally (sideways) from the railing sketch line, which is placed on the edge of stair runs and landings by default.

Unfortunately there is a built-in system default value of 25.4mm, which is one inch.  The logic to this is obscure - it only works if your top rail happens to be 50.8mm (two inches), and where the face of the top rail needs to align exactly with the edge of the run/landing.  Why is this so bad?
  • This never, ever works in the metric world (all but two countries in the world) - even if we have a 50mm top rail there is still an 0.8mm discrepancy every time; Occasionally it might suit a situation in the imperial world, as described above;
  • This never works when the stair abuts a wall (metric or imperial) - see what happens to supports later on.

This default value is infuriating - as you have to correct every single stair railing after placement.  In my opinion it should be a default that we can control in some way (either a 'last placed' setting or in the Revit.ini file);  alternatively it should be a Type property rather than instance.  Please vote here on Revit Ideas if you agree with me - if this blog has helped you out, then please help me out by voting.

2.  Old-Style horizontal rails

The old Type Property dialog box for horizontal rail structure has a separate 'Offset' property for each rail element.  This does not used the word 'lateral' anywhere on the dialog box, so you have to guess which of the three possible directions it will offset (x, y or z), as well as which is positive or negative.

3. Baluster Placement (Individual Balusters)

The Baluster Placement dialog has a separate 'Offset' property for each baluster element.  This does not used the word 'lateral' on the dialog box, so you have to guess that it is a lateral offset property - although there are also Base and Top offsets, so it is easier to identify.

Warning:  This individual Baluster Offset property goes in the reverse direction to most other offsets:  A positive value pushes the baluster outside the stair, while a negative value goes in towards the stair - this is inconsistent with most other railing offsets.

4.   Post Placements

Railing posts are similar to Balusters (with the same reverse direction offset)

5.  Baluster Offset (and Top/Handrail)

Back in the Railing Type Property dialog box, there is another property called 'Baluster Offset' - another guessing game ensues.

This can give very unpredictable results.  It will laterally offset all of the balusters by the same amount;  it does not affect the horizontal rail structure.  With the old style railings, it was confusing enough because the individual Offset goes one way, and the overall baluster offset goes the other way. However, with the new style railings* it is almost incomprehensible :
  • The balusters will all be offset laterally by the same amount.  Unless . . . .
  • If an individual baluster offset value has been applied, it is cumulative, so the individual is added to the master baluster offset property (bearing in mind that a positive value for one may cancel out a negative value in the other).
  • Old style horizontal rails will not be affected (they get left behind).
  • New style 'Top Rails' will be offset.
  • New style 'Handrails' will be offset.

The net result of all this is that the Baluster Offset property may work as a Type control offset for the whole railing, provided that you don't have any old style mid rails - in that case you have to offset each of those in the Rail Structure dialog box.

* New style railings were introduced from Revit 2013 onwards, but old style railings were not automatically upgraded - only if you've swapped to the new style railings!  You may still have old-style railings in your projects.

5A.  Rest

Are you still following all this?   If not, (or you have a headache) just have a rest or lie down for a few minutes, before moving on to the next one.  I can't say it gets any better . . .
Deconstructed Railing

6.  Handrail

New style railing Types have handrail properties - these include "Lateral Offset" for each handrail, which are greyed out. 

The Lateral Offsets are calculated by the system, depending on the Handrail type properties.  This represents the offset of the Handrail centreline from the notional Railing centreline (which is in turn affected by the "Offset from Path" property . . .)
Refer to Rail Hand Clearance Property for how this is calculated.

If you change the 'Hand Clearance' property it will move the centreline location of the Handrail relative to the overall Railing.
  • This has to be done in the Handrail Type properties dialog box, not in the Railing properties.

7.  Right Handrail

The above example assumes a handrail is set to 'Left' Position.  If it is set to 'Right', the whole handrail is mirrored and offsets outside the stair.

8.  Top Rail

Top Rails also have a 'Hand Clearance' property, but unlike Handrails, this is not displayed as a Lateral Offset in the Railing Type properties.

The Hand Clearance property of of the Top Rail most assuredly does affect its Lateral Offset - so it would be mighty useful to have that property displayed, even if you want the Lateral Offset to be set to zero most of the time.

Why oh why is it missing?

One possible reason it is missing might be that the offset direction is the opposite to Handrails - a positive Hand Clearance on a Top Rail would give a negative Lateral Offset.

9.  Sketch Offsets

I would not be surprised if there are other Offset properties that I have missed.
There is at least one more way to move Railings, aside from playing with the properties:
  • Edit the stair sketch and 'Offset' the sketch lines from their original location.
  • I would not recommend doing this on stairs without good reason, as it would make the properties even more confusing.
  • If the sketch lines go outside the run or landing (laterally), you would most likely encounter hosting and height problems - so that is not advisable.

If you are confused by all this, it is hardly surprising.  I will try to shed some light on how to manage these offset properties in future blog posts. . . . .