Stepped Stair Railing Top Rail Extension in Revit

Following on from an earlier post about stepped railings, here is a bit more information about what happens when you try to add Top Rail extensions.

Weird Railing Stuff - part 18

If the lowest boundary line on the railing path has a Slope property "By Host", the railing segment will be horizontal (assuming you have done a Height Correction on the other segments)

To add an extension to the base of the stair railing:

• Tab-Select the Top Rail only

• Edit its Type properties
• Tick the checkbox for "Plus Tread Depth";  Apply or OK

• Nothing happens
• Revit thinks that this segment of the railing is not part of a sloping stair, even though we know it is
• Edit the Extension Length property to 300mm
• This time Revit adds the extension (horizontal), as expected (but still no extra tread depth, unlike the straight handrail on the other side of the stair, where it has both)
  

•  Confusing huh?

Solution

To solve this, the Slope property of the railing segment must be changed:

• Select the whole railing

• Edit the path
  

• Select the last segment of the path
• Change its Slope property to "Sloping"

• Finish the Path sketch

• The Top Rail should now be sloping and have both the 300mm extension (horizontal) and the extra tread depth (sloping)

Both railings should now match

Analysis of Slanted Walls in Revit 2021

Any new modelling feature in Revit is welcome.  Although I have seldom needed to slant walls in a Revit model, it something that people occasionally want to do.  Now that you can easily slant walls in Revit 2021, we can expect to see a huge number of very scary looking buildings going up around the world (and hopefully not falling down).  Builders and structural engineers will probably be cursing Autodesk for years to come for this new feature!

For the first time in many years I did not do any beta testing of this "Shiny new feature" of Revit - so I do not yet know of its limitations or benefits.  I decided to do some very simple testing to see what the software engineers came up with.  Here are my preliminary findings:

Slanted Wall Angles

Once you place a wall in Revit 2021, it has a new property:

• "Cross-Section" - this will be set to "Vertical"

Change the property to "Slanted" and it enables another new property:

• Angle From Vertical
• The angle will initially be set to zero
  

In a section view you can see the wall angle zero being vertical

• In this example there is a room in section to the left of the wall
  
• selected wall is purple
• Room in section is pink
• There is a vertical reference plane where they meet (green dashed line, not yet visible)
• There are several detail lines (dashed) running from the base of the wall (inside face) up at 10, 30 and 45 degrees to vertical.
  

Wall Pivot

I was curious about the wall pivot point:

• Set the angle to 30 degrees
• Notice the edge of the room has moved back from the reference plane;
• The wall pivot point is not the bottom left corner (inside face of the wall);
• The inside face of the wall is not on the detail line.
  

• On checking I realised that the wall 'Location Line' property was set to Wall Centerline
• The wall is pivoting around its centreline base of wall
• This is fair enough - but is a setting to watch out for
• It becomes more obvious when the angle increases to 45

• The wall thickness does not change but the horizontal dimension across its base line increases with the angle.

It is unlikely that you would want the wall centreline to be the rotation point as it is hard to predict where the inside face base will be from its original location (unless you resort to trigonometry).

To solve this:

• Set the angle back to zero
• Change the Location Line to 'Inside Face of Wall' (or Outside face if you want)
  

• Change the angle and it will rotate around the inside face base of wall
• Room edge stays on the original reference plane
• Wall edge aligns with the slanted detail line
  

Change the angle again and it pivots as expected

So far, so good - even if a little tricky.

• Behaves as expected, but is a trick for new players.

Base Offset

What happens when you change the base offset of the wall?

• Try changing the base offset to 1 metre (1000mm)
  

• Oops - the wall is still pivoting down at the level - not the base of the wall (ie. around where the wall base would be if it started down at the base constraint level).
• That is very confusing

• What happens if you combine a base offset and a wall centreline Location Line?
• The end result will be almost unpredictable
• The room extent is nowhere near the actual wall
  

I do not believe that this is the correct behaviour for the wall - I think it should pivot about the base offset height at whatever Location Line you have chosen.

• This is really going to confuse people

[Edit - Plan Views added]

The diagrams above show what happens to the wall in section, so I have added a few snapshots of plan views to clarify (I hope) what to expect:

• Vertical wall
• Inside face of right hand wall on the reference plane
  

• Right hand wall Slanted 45 degrees; Location Line Inside face; zero base offset
• Note that base of wall has not moved (on the reference line):
  

• Right hand wall Slanted 45 degrees; Location Line Wall Centreline; zero base offset
• Note that the inside face of the base of the wall has moved slightly to left (in fact whole wall has moved) - due to pivot point being centre of wall):
  

• Right hand wall Slanted 45 degrees; Location Line Inside Face; 700mm base offset
• Base of wall moved 700mm to right
• Apparent wall location is the same as the wall with zero base offset - but that is what happens at the cut plane height only (a notional drawing convention).  The important thing is that the base of the wall should not move when you slant the wall, but it does.
  

Conclusion:

Should I have done some beta testing and warned the software developers that this was not acceptable behaviour?

I have tried that with several new features in the past - sometimes they have modified things accordingly, but often not.  Often the beta testing process comes too late in the development cycle, and things like that cannot be changed before release.

Either way, I think it is wrong and should be fixed immediately - before people start using it on real projects.  Slanted walls will be scary enough without being built in completely the wrong location.

Next blog post I will be investigating slanted walls and room extents

And following that, 'Why the wall joins don't work in plan' . . . .

Weird Railing Stuff - part 7a - Support Spacing Postscript

I mentioned in my previous post about handrail support spacing that the distance between supports is measured along the length of the handrail regardless of its angle, rather than a horizontal plan distance (which is used by other railing element spacing).  It turns out that it gets even weirder:

Revit Railings Get Weirder and Weirder

I thought I would check where it is measured on the handrail, and whether it takes into account a fillet radius if you have one.

• On a horizontal railing, it measures support spacing on the underside of the handrail
• On a sloping railing, the supports seem to be attached to the handrail a bit higher - you can snap to the top endpoint of the support.  In the example I tested, with a 75mm high support, the top is about 7mm vertically into the handrail.
• This means that the spacing is measured slightly above the underside of a sloping handrail - this may vary depending on the angle and the type of support.  However, I have no desire to investigate any further - this is weird enough already.
• If you have a curved transition from horizontal to sloping handrail (fillet radius), the support spacing measurement transitions (on a radius) from underside of handrail to somewhere above the underside.
• This means that you cannot accurately predict where the supports will end up - unless you do a checking diagram like the one below.  I can tell you, this is the first and last one I will ever do!

 Extension to Floor

I know that you'd never put supports like this on a handrail with a vertical extension to the floor, but I just wanted to see what it does with the spacing:

The answer is that the supports get flipped to the outside of the handrail (what becomes the top when it turns the corner to be horizontal).  However, the spacing between the two supports as it goes from vertical to horizontal is not predictable.  In the example above, the typical spacing is 200mm (just to be certain it doesn't come away from the wall!), but the distance measured orthogonally between those two supports on the corner is only about 190mm - so we are adrift by 10mm.  As I said, it is not easy to predict exactly where the supports will end up.

If we had a start/end indent property, we could at least make a guess, then tweak the indent value until it is exactly where we want the first/last support - without having to unpin the supports (which has its own problems, to be discussed later).  Please go to the official Revit Ideas website and vote up my idea on this

Just to entertain you, here is what Revit does when you have a handrail extension to a wall - note that the support goes to the top of the handrail again (not that you actually want a support when the handrail fixes to a wall, of course!).

More on this subject:

• Weird Railing Stuff - part 7 - Support Spacing
• Weird Railing Stuff - part 8 - Moving Handrail Supports  
• Weird Railing Stuff - part 9 - Handrail Supports on Multistorey Stairs (Revit v2018+)