Pad Footing elevation at bottom is wrong

[3dway]

I have pad footings that are scheduling the incorrect elevation at bottom.

It's out by 7/8".
The pad footings show at the underside of the slab where they should be.
If I dimension from the reference level, (top of foundation and project base point 0.0) I get a different dimension than is scheduled. BIG problem.

I've been reading that this is somehow changed when the footings attach to a column or grade beam. Any solution?

[david_peterson]

Only way I know of it changing is if it's set to project coords or sharded coords.
Did you check the elevation of both the project base point and the survey point?
The elevation would change if it's connected to a column (not sure on grade beams) but only if the base elevation of the column changed.

[Craig_L]

It is true that pad footings being connected to columns will push down as the column does.

I typically model my columns up to 35mm short of the pad footing. This leaves room to detail or model in a grout pad, + base plate and keeps the column from being "attached" to the pad footing.
This poses problems only if you are using the analytical model for analysis.

I do not attach walls or columns to footings, because it will cause this problem. Another way to stop it is to model your footing to a reference plane, and lock the face of the footing using the align tool (then click the lock symbol) to the reference plane, and lock your reference plane with a dimension to a fixed level (dimension to a level and again click the lock button when the dimension is placed, or selected). Test this out, but I am 99% sure the locked ref plane will work for you.
I should mention also to ensure that your "fixed" levels are locked, or Revit will prioritise the level being locked to the reference plane, and should this somehow get pushed down (or up) without you realising, would change the RL of your "fixed" level.

Of course, if you've modelled all of your footings alread then this is not going to help.
Short answer is yes, columns will push your footings down and revit will NOT warn you about it, so its something to be aware of.

[david_peterson]

Funny, if the column is attached to the footing I always get a warning.
Instead of leaving a gap we created a column that is the base plate, grout and anchor rods. Work great for us.
The ref plane is the other way to do it. I've never experience a footing moving on it's own. Again if the footing is attached to the column, when the bottom of column elevation changes, the footing changes as it one should expect.

[Craig_L]

Yes, I had forgotten about that warning...
However wall strip footings, will not warn you if your wall depth changes.

[3dway]

My columns show in the right place, dimension correctly, but the underside of footing field is incorrect. I thought it was project base point related, but I've adjusted those with no change to the underside of footing property. I think its called "elevation at bottom".

Is it possible that this field holds a value from when the footing was created? I've changed the level that they're associated with, changed my project base, and survey point, both by moving them and typing the correct number in the elevation field. Even new footings show the same problem.

Is it possible that they're reading to Revit's inaccessible "actual" coordinate system that I've heard about. I'm 22mm off and when I first checked the project base point, that's how far it was off the TOF. I moved it and re-entered the elevation, and re positioned the survey point. I've probably done this wrong somehow.