Toposolid versus Toposurface: What changed in Revit 2024?

For anyone who last set up a Revit site model in 2022, the comparison sounds live: Toposolid vs Toposurface, weigh the options, pick the one that fits. In current Revit, that comparison is mostly historical. Toposurface was removed in Revit 2024. So were Building Pads. So were Split and Merge Surface. The old workflow is not being deprecated slowly, it is already gone.

That does not make the comparison pointless, because a lot of live projects still contain Toposurfaces from earlier files, and the migration path is not automatic. But the useful framing has changed. It is no longer "which one should I use." It is "what do I do with the Toposurfaces I already have, and how do I use Toposolid without repeating the mistakes people made in 2024."

This is the honest version of that guide.

What Autodesk removed and what took its place

The relevant Revit 2024 site-tool changes, in one place:

Toposurface was replaced by Toposolid. You cannot create a new Toposurface in Revit 2024 or later.
Building Pads were removed. You now cut buildings out of a Toposolid using voids or Graded Regions.
Split Surface and Merge Surface were removed. You now edit a Toposolid the way you edit a Floor.
Subregion became Sub-Divide. It still exists, but the underlying element is different.

Existing Toposurfaces in upgraded files are not deleted. They stay in the model but become read-only. You cannot add points, adjust levels, or change materials. If you need to edit them, you convert them.

Autodesk's official upgrade path is a command called Generate Toposolid. Select the legacy Toposurface, click Generate Toposolid on the Modify ribbon, pick a base level and a type. Revit builds a new Toposolid that copies the shape, and leaves the old surface in place. That gets you an editable version. It also has a few well-known catches, covered below.

What Toposurface did (and where it still lives)

A Toposurface represented terrain as a triangulated skin between elevation points. No thickness, no layered type, no proper physical assembly. You built it by importing points from a CAD file or CSV, or by placing points by hand.

For a decade it did a reasonable job of what most architectural projects need: represent the existing ground, cut a section that reads correctly, host site components, produce planning visuals. Its limits were also well known. No build-up meant no soil depth, no paving make-up, no landscape assembly as a real modelled thing. Around basements and foundations it often needed help from floors, pads, voids, and detail components.

If you have a live project on Revit 2022 or 2023, Toposurface is still the tool of the day and there is no reason to abandon it mid-project. The moment you upgrade, the calculation changes.

What Toposolid is (and how it has evolved)

Toposolid is a solid element with a point-based terrain shape. In practice it behaves more like a Floor than the old Toposurface: types, layered structure, materials with thickness, hosted elements, and predictable interaction with cuts.

It landed in Revit 2024 unfinished, and the community said so loudly. The 2024 release could not do sub-division thickness properly, hosted elements did not attach to cut faces correctly, Shaft openings punched all the way through rather than stopping at the base of the shaft, and editing performance on large sites was slow enough to become its own talking point. Landscape architects in particular were vocal on the Autodesk community, and some firms held projects on Revit 2023 rather than upgrade.

Revit 2025 improved most of that:

Excavate tool, for cutting the volume of a Toposolid to the top of an intersecting floor or slab. Roads, paths, parking areas become modelable properly.
Shaft openings now respect the bottom of the shaft rather than cutting through the whole Toposolid.
Hosted elements attach to the cut face rather than the original extents. Trees and site components follow the excavated surface.
Mass-face to Toposolid creation.
Smoothing for shaded views.
Contours visible during edit.

Revit 2026 addressed the remaining sub-division awkwardness:

Negative sub-division values, so roads and recessed features can be modelled as sub-divisions rather than as separate elements.
Sub-division types, not just materials. You can now schedule sub-divisions by type.
Sub-divisions became a sub-category, which means Visibility/Graphics and Object Style overrides work per sub-division.
Generate Toposolid now auto-creates recessed sub-divisions from legacy subregions. That is a real quality-of-life win for anyone migrating old files.

The version story matters because Toposolid is the tool going forward, but which version of Toposolid you have makes a substantial difference to what is actually usable. Advice written against Revit 2024 does not always apply cleanly to 2026.

The practical differences that still matter

For anyone weighing what the change means for their workflow, the differences worth internalising:

Geometry: skin versus solid

Toposurface was a triangulated skin. Toposolid is a solid element. This is not a nuance. It changes how the terrain interacts with foundations, basements, hosted floors, walls, and voids. Section drawings that used to need supplementary detail elements often now read as real modelled conditions, provided the type is set sensibly.

Type structure and materials

Toposurface had one material per subregion and no build-up. Toposolid has types with layered structure, thickness, and material overrides per sub-division. You can model a hard-standing build-up as a Toposolid type, or leave existing ground as a simple single-layer type. The temptation is to model every soil horizon from the geotechnical report. Resist it. A clearly-named simple type usually earns its place better than a five-layer showcase build-up nobody edits.

Boundaries and control

A Toposurface's perimeter was defined implicitly by where you placed points. A Toposolid has a sketched boundary you can control directly, similar to a Floor. That means concave sites, curved edges, and site-boundary matches are more reliable, and less prone to the "why is my terrain a rectangle" problem people used to work around by hand.

Existing versus proposed

The old approach was phased Toposurfaces or graded regions, depending on the release and office standard. Toposolid uses phasing the same way, but the physical separation between existing ground and proposed ground is cleaner because both elements have thickness. Set the imported terrain to Existing and use Graded Region for proposed. Cut-and-fill volumes schedule off the Toposolid, which the old Toposurface could not do as directly.

Performance and point density

Both elements were sensitive to too many points. Toposolid is more sensitive, because editing a heavier solid element with layered structure and hosted geometry is more expensive than editing a skin. The community reports of Toposolid taking 10 to 15 seconds to update a single point on a large site are not exaggeration. They mean the input dataset needs discipline.

Aim to keep working Toposolids under about 10 to 15 thousand points. Revit 2024 and 2025 will downsample CSV imports to 10,000 automatically, which is a hint rather than a hard rule to follow. Revit 2026 lets you raise the limit via a `Revit.ini` edit, but performance still degrades past that range.

Migrating a legacy Toposurface

The Generate Toposolid command handles the common cases, with a few things to know before you run it:

Building Pads are ignored, which is Autodesk-speak for deleted. If you were cutting the building footprint into the ground with a pad, that hole disappears on conversion. Re-cut it with a void or an Excavate operation on the Toposolid, or in Revit 2026, using a negative sub-division.
Subregions become sub-divisions. In Revit 2024 the conversion loses the material thickness fidelity. Revit 2026 auto-creates recessed sub-divisions from subregions, which is much closer to the original intent. If you can convert on 2026, do that.
The old Toposurface stays in the file after conversion. Read-only, but visible. Keep it during the review, delete it once you are confident the Toposolid matches.
Spot Elevations and Contour Labels hosted on the Toposurface tend to re-host to the new Toposolid, at least in practice, but check the ones that matter for your documentation.
Coordinates carry across. You do not need to re-align the terrain to the project. If your original Toposurface was correctly placed, the Toposolid will be too.

If your project has a shared coordinate workflow with a civil consultant, run the conversion, then run a spot-check on a few known survey points. Cut a section through the building footprint. Confirm existing levels agree with the source data. Migration is where silent drift shows up.

The decision framework, honestly

The scenarios that actually matter:

Starting a new project on Revit 2024 or later. Toposolid. There is no other choice. Set up the type and thickness once, put the imported terrain on the Existing phase, and use Graded Region for proposed grading. If you are on 2024, know that some features arrived in 2025 and 2026. If you are on 2026, use the sub-division improvements.

Live project on Revit 2023 or earlier. Toposurface. Do not migrate mid-project unless you have a specific reason. Upgrading a live model to a newer Revit release converts every Toposurface to read-only, and Generate Toposolid is a decision, not a background upgrade step.

Upgrading a project from 2023 to 2024 or later. Plan the migration deliberately. Convert one Toposurface at a time using Generate Toposolid. Expect Building Pads to disappear on conversion, and re-cut them as voids, excavations, or (on 2026) negative sub-divisions. Keep the read-only original in the file for the review period. Update phasing and any type parameters the office standard depends on.

Landscape or civil-heavy project. Toposolid on 2025 or later, ideally 2026. The 2024 release genuinely struggled with landscape workflows, and the workarounds (Revit 2023 for topography, upgrade for everything else) are not a good long-term strategy. 2026 is the first Toposolid release that fully replaces what landscape teams were doing with Toposurfaces.

Detailed civil coordination. Neither element replaces a proper civil model. Link the civil consultant's surface, keep the architectural Toposolid as a reference, and make sure the coordinate strategy matches. This has not changed.

Point data discipline

Whichever element you end up with, the input matters more than the tool. Terrain from a broad public elevation source is fine for feasibility, concept, and coordination. It is not a substitute for a project survey. Record the source, the coordinate reference, the vertical datum, and the capture date next to the file. Match point spacing to the decision (5 to 15m for concept, 1 to 3m for grading zones, closer only where the design demands it).

A well-prepared CSV in the right coordinate system produces a Toposolid that behaves ordinarily. A dense, wrong-datum CSV produces a Toposolid that will haunt every section for the rest of the project. The tool change did not remove the need for discipline at the front end.

For teams generating that CSV from open data, Topo-grapher produces a boundary-clipped XYZ file in your chosen coordinate system, at a point density you set explicitly. It does not fix Revit's site tools. It gives you an input the Toposolid tool can handle without complaint.

Generate a Toposolid-ready CSV free →

Frequently asked questions

Is Toposurface still available in Revit?

No, not for creating new terrain. Toposurface was removed in Revit 2024. Existing Toposurfaces in upgraded files remain in the model as read-only elements, and you can convert them to Toposolid using the Generate Toposolid command on the Modify ribbon.

Do I need to convert my Toposurfaces immediately after upgrading?

Only if you need to edit them. A legacy Toposurface upgraded to Revit 2024 or later will display and print correctly, it just cannot be modified. If the terrain is stable and only there for context, you can leave it as-is. If it needs any change, convert with Generate Toposolid and expect Building Pads to be lost in the process.

What happens to Building Pads on conversion?

They are ignored, which is Autodesk-speak for deleted. Re-cut the building footprint into the Toposolid using a void, the Excavate tool (Revit 2025 and later), or a negative sub-division (Revit 2026).

Which Revit version has the best Toposolid?

Revit 2026 is the first release where Toposolid is broadly comparable to what landscape architects were doing with the old Toposurface. Revit 2025 was the first usable version, adding Excavate and proper Shaft behaviour. Revit 2024 is functional but genuinely limited for landscape work.

Toposolid vs Toposurface for performance, which is faster?

Toposurface, at equivalent point counts. Toposolid is a heavier element because it is a solid with a type structure. If a project team is unhappy with Toposolid performance, the usual cause is too many points in the source dataset, or one enormous Toposolid where several smaller ones would edit faster.

Can I still model layered soil or paving build-ups?

Yes, and this is one of the genuine wins of Toposolid over Toposurface. Set the Toposolid type to a layered structure the way you would set up a Floor. Do not over-complicate it. One or two named types (Existing Ground, Hardstanding) usually earn their place, five-layer geological showcases usually do not.

Do I need to convert Toposurfaces if I only need to render?

No. Read-only Toposurfaces still display and export, and their appearance carries through most rendering and view exports. The conversion is only necessary when you need to modify the element.