Monday, 15 December 2008

Revit - Modelling balcony slab with sloped edges

Here's an interesting modelling challenge set by Nilanjana of the London Office. She wanted to quickly produce a balcony, based on the sketch below, for a large high rise residential scheme.

problem

You will see from the diagram above that the majority of the balcony is 450mm deep and is flat as indicated by the blue area. The balcony then falls away on three edges to only 150mm thick. You will also notice the balcony is not rectilinear as indicated, with three sides at different angles.There are a number of different ways to tackle this.... create a family, an in-place family? All have their merits, but at the concept stage of a project you don't always have time to produce what in essence is actually a rather complex family to create. So the easiest way to create the balcony is in four separate elements.

So start by sketching out a few reference planes to define the extent and shape of the balcony.

Next create a new floor slab type which is 450mm thick. Edit the type properties of the construction of the floor slab and set the structure "variable" radio button is ticked. This will ensure that that slab is flush on the underside after you have edited the slab.

vraiable

Next model four separate slabs based on the reference plane sketches.

4 slabs

You can then slab edit the edges of the three slabs which need to slope away using the sub-element edit tools. Select one of the floor slabs you created and the sub-element edit tools will appear in the options bar.

sub edit

Next select the edit points/edges tools, then select the outer edge of the slab you want to edit and alter the elevation from 0mm to -300mm; this will drop the whole edge of the slab and it will slope as required.

edge edit

Now do this for all the other edges which need to fall away.

dropped edge 

For extra finesse, use the join geometry to clean up all the floor slabs.

result  result

One could argue that this is not a purist approach to the BIM problem because you end up with four slabs rather than one, but at that concept stage where you want to convey an idea, this approach is ideal.

2 comments:

Alexander Ruhdorfer said...

Dear Mr. Light!

At first, sorry for my english - I speak German.
I hope that I understood the problem.

My way to create the balcony:
I have created the balcony slab with the slopes as one slab.

It is very easy:
1.) create the slab
2.) select the slab and draw the five break-lines with the editing tools.
3.) select the endpoints on the outside of the slab (TABing until they are green, then click) and modify the height (-0,30) -> READY.
It only takes 2 minutes to do this.

Greetings from Austria
Alex

boyantcho said...

how do you do reverse the slope. What I mean is to have a balcony slab that is getting thinner to the end of the edge, but the top surface is flat and the underside of the balcony is sloping away.

Thank you in advance.