# Surface Finish · Common Problems
Condensed English edition.
# Quick reference
| Symptom | Cause | Fix |
|---|---|---|
| Command wants a room but nothing can be selected | Rooms not created / finish not modelled separately | Prerequisite |
| Public parameter offset does nothing / rejects negative values | Wrong parameter | Not a top/bottom offset |
| Ceiling built with a slab is one board thickness off | Slabs cannot substitute for ceilings | Don't use slabs for ceilings |
| Threshold stone won't generate | Slabs on both sides don't exist yet | Threshold prerequisite |
| Roof creation fails | Known first-run behaviour | Roof creation fails |
| Material quantities wrong after merging slabs | Over-merging | Don't over-merge |
| Skirting can't be hidden in plan | Skirting was built into the wall type | Create skirting separately |
| Box-select opening cuts the wrong wall | Selection window caught another wall | Box-select scope |
# Prerequisite: rooms + separate modelling
- Most surface commands are room-based, so rooms must exist first
- Model finishes separately from the main structure
Why separately
Many commands generate and count per room and per block (e.g. material quantities after merging slabs). Mixing finishes into the structure makes later changes and quantity take-off painful.
# Public parameter offset is not a top/bottom offset
- The offset here is the offset from the wall (a public parameter), not the wall's top/bottom offset — completely different concepts
- Negative values are not accepted
- Decide the offset distance up-front, then pick rooms/walls, to avoid rework
# Don't use slabs for ceilings
A very common modelling mistake
Using a slab instead of a ceiling for a suspended ceiling leaves you one board thickness off — you may measure only 2.2 m.
Fix: generate suspended ceilings with the ceiling command.
# Threshold stone requires slabs first
Prerequisite
Threshold stone generates its extent from the slab edges on both sides of the opening, so the slabs must exist first.
- Interior door openings: from the interior slab edge on each side
- Exterior door openings: from the interior slab, extending 200 mm outward
# If roof creation fails
Symptom: The first roof creation attempt fails.
Fix (simple and effective):
- Manually create any roof in the project
- Delete it
- Run the plugin command again — it normally works
The same pattern applies to other "first run fails" cases: do it once natively in Revit to warm up the environment for the plugin.
# Don't over-merge slabs
Cause: the plugin reports material per room and per block. Merge too much and quantity take-off stops matching.
Fix: merge only where needed.
# Create skirting separately
Benefit: skirting created separately can be hidden in plan views.
If skirting is built into the wall type, it cannot be hidden.
# Box-select scope for openings
WARNING
Only select the wall segments that need openings — do not catch other wall segments.
Applies to typical wall-based openings (doors, windows) and to curtain-wall types that can host embedded openings for finish-wall openings.
# Other notes
- Faux layered wall: use the dedicated command; don't try to stack base walls
- Multi-layer edge (colloquially "slab edge") and wall edge are separate commands — don't mix them
- Ceiling secondary processing and cove capping build on an existing ceiling; keep the order
- Veneer has a toggle called "multi-select"; it also has an extension use that acts as a general "apply finish" tool
- Skim coat / exposed ceiling spray are what you use when you need room wall/ceiling/floor areas; if you need room surface areas, you can create the model with skim coat and then extract the areas
