Slab depressions - Floor family?

[revituser195]

Hello, (2011 or 2012 RAC)

I've read several threads on creating floor slab depressions by doing the following:

- Creating an in place family that is a void, but how does this get placed in the floor category and only interact with floors?

- Create a new family that is a void. If I try to create a new family, I don't see a floor based family template. Generic Floor Based is there, but when importing into the project it is listed within the Generic category.

How do these show up in the Floor category?

Thanks,
Rob

[renogreen]

When you create the in-place family, the categories will come up...select floors. Model a void form. When finished creating the void you will need to cut the void geometry from the floor. Now it is part of the floor.

[revituser195]

Ok, was confused by in place mass. So home / build / component / model in place.

When using this, a void is created in the Floors category, but when trying to finish, there is an error stating the void does not cut anything and use the Cut Geometry tool. The only options are Delete Elements and Cancel.

Why isn't this interacting with the floor slab already in the model? The orange void clearly extends through the floor slab.

Thanks again,
Rob

[revituser195]

While editing the in place void, geometry / cut / select floor slab / select void, then finish. This seems to work, is this correct?

Thanks

[david_peterson]

I'm often confused by this one. Why not just model another floor and lock the boundaries to the overall floor? Adding voids generally only causes issues later on.
Also when you depress a slab, most times you still need to maintain slab thickness. Which requires you to model another floor anyway.

[renogreen]

David, I've done a few floor slab depressions, not a bunch, but haven't had any issues later on. What sort of issues?

[david_peterson]

I guess I should have clarified. I've never used a void mass to create a slab depression. I've used voids a ton for creating pier pockets at exterior walls. After you place the void in a wall, you can't modify the wall without having to redo the void. I was just under the assumption that you'd run into the same type of error with a slab.
After you place a void in wall, and you need to say add a footing step or you need to slice the wall for some other reason, you get an error from revit telling you that it can't be done. I believe this is due to revit not being able to identify which wall the void should belong in (ie the newly created via the slice or the one that the void was originally placed in.

[renogreen]

I just ran a little check and was able to modify a slab after using a void for a depression. Good to know.

[revituser195]

Can't dimension to the void :o|. Tried putting Model and Symbolic lines in the in-place void but you can't snap or align to the void.

Any suggestions here?

[cliff collins]

Try using another floor slab instead, and join geometry. Does the depression go only partially thru the main slab's thickness? i.e. not an actual "hole" which penetrates it?

cheers

[revituser195]

Correct, it is a depression, not a hole.

[cliff collins]

One way to approach this without using voids:

You can place a second floor, and set it to be offset from the Level, then edit the sketch of the main floor
to achieve the depressed slab.

see attached.

cheers

[revituser195]

Thank you for the reply, but really? There isn't a better way to do this? 3 different objects - 2 duplicate objects to achieve a basic form?

Again, thank you for the reply, I'm not attacking your response. There should be a way that won't allow for human error like this.

[renogreen]

The reality is that the method of creating another floor as both Cliff and Dave have suggested is probably fewer steps and fewer problems afterwards than using the void method. I think I'll try it next time I have a slab depression.

[gtarch]

And if you need to thicken the slab on the bottom side to maintain a minimum thickness, the 2 floor object approach is needed, or something like it.

[Craig_L]

Further to Gtarch's comment - lets assume that the setdown area is a wet area, with falls to a drain.
You can "modify points" in this slab without having to affect the other main area of the slab.
Its really just a much easier way to work, allows things like thickenings, allows you to have the setdown area following a fall, or even set it as a different grade material (perhaps its a screed) or you can simply join it to your main slab and it seemlesly folds into the main slab.