Join Geometry, Disallow Join and Wall Joins all contain the word "join" and sit around the same Geometry panel, so beginners mix them up. They do three different jobs. Revit join geometry connects two overlapping elements so Revit subtracts the shared volume. Disallow Join stops one wall end from joining other walls. Wall Joins changes the shape of a junction between walls that are already joined.
This article runs all three commands on one Revit 2027 model: a wall, a floor, a column and a few wall corners. Each command has before and after images plus the volume change. For a structured learning path, see the Learn Revit course.
How the three commands differ
| Join Geometry | Disallow Join | Wall Joins | |
|---|---|---|---|
| Acts on | Any two overlapping elements: walls, floors, columns, beams, roofs | One end of one wall | The junction between joined walls |
| What it does | One element cuts the other, the shared edge disappears, overlapping volume is subtracted | The wall end no longer joins, even after the wall is moved | Changes the join type (Butt, Miter, Square off), join order and display |
| Changes quantities | Yes | Yes, because the walls stop joining | No volume change, only the junction shape |
| Where | Modify › Geometry › Join | Right-click a wall end, or inside Wall Joins | Modify › Geometry › Wall Joins |
In short: two different elements overlap, use Join Geometry. Two walls meet with the wrong corner shape, use Wall Joins. Two walls must not join, use Disallow Join.
Revit join geometry: joining overlapping elements
According to Autodesk's Join Geometry page, the tool creates clean joins between elements that share a face, such as walls and floors. In a project it does not merge the two solids. One element cuts the other according to these rules:
- Walls cut architectural columns.
- Structural elements cut host elements: walls, roofs, ceilings and floors.
- Floors, ceilings and roofs cut walls.
- Gutters, fascias and slab edges cut other host elements.
Steps:
- Go to Modify › Geometry, click the arrow next to Join and choose Join Geometry. The status bar reads FIRST pick: Select solid geometry to be joined.
- Click the first element, for example the wall.
- Click the second element, for example the floor.
- To join one element to several others, turn on Multiple Selection on the Modify | Join Geometry contextual tab before picking. Revit 2027 uses this button instead of the older Multiple Join check box.
- Press Esc twice to finish.
Which element cuts which does not depend on pick order. In the example below the wall was picked first, yet the floor still cut the wall, following the "floors cut walls" rule.
How Join Geometry changes quantities
Before joining, Revit gives each element its full volume, so the overlap is counted twice. The sample model: a 200 mm masonry wall 6 m long and 3.6 m high, a 250 mm concrete floor 8 × 3 m, and a 300×450 concrete column on the wall line.
| State | Wall | Floor | Column |
|---|---|---|---|
| Not joined | 4.320 m³ | 6.000 m³ | 0.486 m³ |
| Wall joined to floor (floor cuts wall) | 4.020 m³ | 6.000 m³ | 0.486 m³ |
| Switch Join Order (wall cuts floor) | 4.320 m³ | 5.700 m³ | 0.486 m³ |
| Wall also joined to column | 4.104 m³ (with wall cutting floor) | 5.700 m³ | 0.486 m³ |
The differences match the geometry: 6 × 0.2 × 0.25 = 0.300 m³ shared by wall and floor; 0.3 × 0.2 × 3.6 = 0.216 m³ shared by wall and column.
A clean plan does not mean a join. A structural column placed on a wall already looks as if it cuts the wall, with no wall lines through it. The plan looks identical before and after Join, but before joining, the wall volume still includes the part inside the column. You cannot spot this double count from the plan.
Columns and floors need care too. Joining a concrete column and a floor in Revit 2027 makes the floor cut the column, even with the floor set to Structural: the column drops from 0.486 to 0.452 m³. Many offices want the column to run through the slab. Then use Switch Join Order: the column returns to 0.486 m³ and the floor drops to 5.966 m³. Both are concrete, so the section looks the same in both cases; only the numbers differ.
How to assign the beam–slab overlap and read totals after joining is covered in concrete quantities in Revit.
Switch Join Order and Unjoin Geometry
Switch Join Order swaps the cutting and the cut element of a joined pair. It is in the same Join menu:
- Go to Modify › Geometry › Join › Switch Join Order. The status bar reads FIRST pick: Select element to which another element is joined.
- Click the first element, then the second.
- Check each element's volume in the Properties palette.
In the image above, after Switch Join Order the masonry wall runs through the floor: the wall keeps 4.320 m³ and the floor drops to 5.700 m³. With different materials the result shows in section. With the same material you have to read the numbers.
Unjoin Geometry returns a joined pair to its original state: start the command and click the two elements. Use it after a wrong join, or before moving an element away without carrying the old join along.
Wall joins revit: changing the junction between walls
Walls that touch join automatically as a Butt join, and Revit cleans up the plan display (Autodesk: About Wall Joins). The Wall Joins tool edits that junction. It works on junctions of up to 4 walls; for more, see Autodesk's Edit Complex Wall Joins page.
- Open a plan and go to Modify › Geometry › Wall Joins.
- Hover over the junction and click inside the grey square. To edit several junctions, draw a selection box around them or hold Ctrl and click.
- On the Modify | Wall Joins contextual tab, pick the join type and display.
- Click Modify to finish. The temporary solid lines shown while editing do not print.
| Option | Meaning |
|---|---|
| Butt | Default. One wall runs through, the other stops against it. Previous/Next choose which one runs through |
| Miter | Both walls are cut along the bisector. Not available for slanted walls |
| Square off | Squares the wall end to 90°. At a right-angle corner it looks like Butt; the difference only shows at angled corners |
| Clean Join | Removes the lines between layers of the same material |
| Don't Clean Join | Keeps the boundary between the wall ends |
| Use View Setting | Follows the view's Wall Join Display property |
With layered walls and Clean Join, Butt and Miter look almost the same because Revit wraps the layers. Switch to Don't Clean Join to see the real junction.
Clean Join and the Wall Join Display property
With Use View Setting, cleanup follows the view's Wall Join Display property in the Properties palette. It has two values:
- Clean all wall joins: cleans every junction, even between different wall types. This is the default for plans in the template.
- Clean same type wall joins: cleans only junctions between walls of the same type. Different wall types keep a dividing line.
The Wall Join Display field can only be changed when the view is at Coarse detail. At Medium and Fine it is locked. If the field is greyed out, set Detail Level to Coarse first.
Drawing walls, Join Status while drawing and the Priority table that decides which layer runs through a junction are covered in how to draw walls in Revit.
Disallow join revit: stopping a wall end from joining
By default Revit joins two intersecting walls. Disallow Join blocks that for one end of a wall. According to Autodesk: Disallow Wall Joins, it is used to keep expansion gaps between walls, or to fix a complex junction that joins badly.
Method 1, right-click:
- Select the wall. The wall end shows a blue dot (the wall end control).
- Right-click the dot at the end you want to free.
- Choose Disallow Join.
Method 2, in Wall Joins: select the junction and click Disallow Join on the contextual tab. Autodesk notes that this sets Disallow Join on every wall end at the junction. To rejoin, draw a selection box around the junction to select all wall ends, then click Allow Join; a single click selects only one end.
After disallowing, the walls stop joining: both stop at the other wall's centreline, leaving an overlapping square at the corner. Select the wall again and a small icon appears above its end; click it to switch back to Allow Join.
Disallow Join belongs to the wall end, not to the location. Move the wall elsewhere and that end still won't join any wall.
Example: a 20 mm expansion gap between two aligned wall segments.
- Select the first segment, right-click the end control at the joint and choose Disallow Join.
- Do the same for the end of the second segment.
- Pull the first wall end back 20 mm, or edit the temporary dimension.
Note: switching back to Allow Join does not pull the wall to close the gap. Drag the end back yourself.
Combining Disallow Join and Join Geometry at complex junctions
Autodesk suggests: when a wall added to a complex junction gives a bad result, disallow its join and then use Join Geometry to clean it up. On a 200 mm wall corner, one step is missing:
- Disallow Join on the horizontal wall end. Both walls stop at each other's centreline, with an overlap at the corner.
- Join Geometry the two walls. The overlap lines disappear, but the outer corner has a 100 × 100 mm notch. Join Geometry only subtracts overlap; it does not extend walls.
- Drag the horizontal wall end out by 100 mm, half the other wall's thickness, to the outer face. The corner is now closed.
When you only need a wall end to stop in the right place, Trim/Extend is faster than dragging. Join Geometry also works with in-place masses; see model in place in Revit.
Common problems
| Symptom | Cause | Fix |
|---|---|---|
| Concrete volume higher than a manual takeoff | Overlapping elements not joined, overlap counted twice | Join the overlapping pairs and compare totals |
| Plan looks clean but wall volume includes the part inside the column | The structural column only masks the graphics | Join Geometry the wall and column |
| Floor cuts the column, against the "column runs through" convention | Revit 2027 lets the floor cut the column on Join | Switch Join Order for the column–floor pair |
| Error when joining | The elements do not touch or overlap | Check levels and positions; see Cut or Join Geometry Fails |
| Two walls touch but a line remains | One end is set to Disallow Join, or Display is Don't Clean Join | Allow Join; set Display to Clean Join |
| Wall Join Display is greyed out | The view is at Medium or Fine detail | Set Detail Level to Coarse, then edit |
| Square off looks the same as Butt | The walls are perpendicular | Square off only differs at angled corners |
| Outer corner notched after Join Geometry | A disallowed wall stops at the other wall's centreline | Drag the wall end to the outer face |
FAQ
Can Join Geometry join two walls?
Yes, but it is rarely needed. Touching walls join automatically and the junction shape is edited with Wall Joins. Join Geometry between walls is mainly used after Disallow Join, or for parallel walls that overlap.
Does pick order matter in Join Geometry?
In Revit 2027 it does not decide which element cuts. Revit applies rules by category. Use Switch Join Order afterwards to change it.
Can I join many elements at once?
Turn on Multiple Selection to join one element to many. To join a whole model, use Dynamo or an add-in; see Revit add-ins.
Does Disallow Join work for beams?
Yes. Right-click the blue dot at the beam end and choose Disallow Join. According to Autodesk: About Disjoining Structural Framing Elements, it disjoins both the physical and the analytical model at that end.
In short, use revit join geometry when two overlapping elements must share their volume correctly; use Wall Joins to change the junction between walls; use Disallow Join when a wall end must not join. After every join, check the volumes in Properties rather than trusting the plan.