How to Convert a Multi-Story Floor Plan to 3D (Practical Guide, 2026)

The short answer

No consumer AI floor-plan-to-3D tool auto-stitches multiple floors into a single walkable 3D model as of mid-2026. That includes Ritn3D, Planner 5D, Coohom, Floor-plan.ai, HomeByMe, CubiCasa — everyone.

The working pattern is straightforward:

1. Convert each floor separately.
2. Present them side-by-side in a listing, or manually stack them in Blender/SketchUp for a single visualization.
3. For 3D printing, print each floor as its own STL and physically stack them.

This post is the practical version of "how do I actually do this today with the tools that exist." Skip to the 3D printing section if that's your goal.

Why nobody has shipped auto-stitching yet

Multi-floor auto-stitching sounds simple ("just stack them") but three real problems have to be solved together for a good user experience:

1. Floor alignment. The exterior walls should line up between floors — if they're off by half a meter, the stack looks wrong. The AI needs to detect and align them, or the user needs a UI to correct.
2. Stairwells and voids. A two-story house has a stairwell that punches through both floors. The 3D model needs to represent that void correctly, or the upper floor sits on top of the stair space and the walkthrough breaks.
3. Story selection in the viewer. The user needs to switch between floors, or fade the upper floor when walking through the lower one. That's UI work, not AI work.

None of the tools I tested have all three. What they typically have is single-floor conversion that produces a good result on floor 1, then requires you to run floor 2 as a separate project.

The two working patterns

Pattern A: Floor-by-floor with side-by-side sharing

For most real estate listings and homeowner visualizations, this is the practical path.

1. Convert floor 1. Upload the ground-floor plan (PDF or JPG). Review the detected walls. Generate the 3D model.
2. Save the share link. Copy the shareable browser link — it opens in any browser with no install.
3. Convert floor 2. Upload the second-floor plan as a separate project. Same review, same generate step.
4. Save that share link too.
5. Present both. In a listing description, "Ground floor: [link] · Upper floor: [link]" works fine. Buyers open each in their browser and walk each floor separately.

Time: about 5 minutes per floor including review edits. A two-story house takes ~10 minutes end-to-end.

Cost on Ritn3D: two of your monthly renders (2 of 3 on Free, 2 of 20 on Pro, 2 of 40 on Pro+). Share links are unlimited.

Pattern B: Manual stacking in Blender/SketchUp

For architects and hobbyists who want one integrated 3D model, the process is:

1. Convert each floor in Ritn3D Pro+.
2. Download each as GLB (Pro+ includes 10 GLB downloads per month).
3. Import both into Blender or SketchUp. Each floor imports as a separate object.
4. Align them vertically. Set floor 2's Y-position to floor 1's ceiling height (typically 2.7m or 3m). Match corners on the same exterior grid.
5. Cut the stairwell void. Delete the floor mesh above the stairwell area on floor 2 so the stairwell reads as an open void through both stories.
6. Export as a single model for presentations, walkthrough animations, or upload to your favorite web viewer.

Time: about 45 minutes per house for someone comfortable in Blender, longer for a first attempt.

Cost on Ritn3D: two of your monthly renders plus two GLB download credits. So a two-story house = 2 of 40 Pro+ renders + 2 of 10 Pro+ downloads.

This gives you the single-integrated-model experience the tools don't yet ship natively.

Printing a multi-story house in 3D

This is where Pro+ users get the most consistent results, because 3D printing sidesteps the "one integrated walkable model" problem entirely — you just print each floor as a separate physical object and stack them.

Process:

1. Convert each floor in Ritn3D. Review the detected walls, edit if needed.
2. Export STL for each floor. Pro+ includes 10 STL downloads per month. A two-story house is 2 credits, a three-story is 3.
3. Choose scale. 1:100 is standard for a single-family home — a typical 100m² floor prints to about 100mm × 100mm at 1:100, which fits comfortably on a 220mm × 220mm print bed with room to spare. Larger houses may need 1:200 to fit.
4. Slice. Open the STL in your slicer of choice — Cura, PrusaSlicer, Bambu Studio, and Lychee all handle Ritn3D's manifold STL export without mesh-repair steps. Set a reasonable print orientation (walls up) and enable minimal supports for window/door overhangs.
5. Print each floor. Print time on FDM is typically 3–6 hours per floor at 1:100. SLA and SLS produce a smoother finish but take longer per part.
6. Stack physically. A small wooden dowel (2–3mm) drilled through the corners of both prints keeps them aligned. Some hobbyists mount the whole stack on a laser-cut base plate for display, or add an acrylic sheet between floors to show the stairwell void.

Cost breakdown on Ritn3D Pro+:

• 1 render per floor (2 of 40 monthly for a two-story)
• 1 STL download per floor (2 of 10 monthly)
• Extra credits ($3.99 each) roll over month to month — useful if you're building a portfolio of multiple models

For 3D print hobbyists building architectural miniatures, this is the standard workflow. See the 3D printable floor plan page for slicer settings, wall-thickness recommendations, and printer compatibility notes.

What to watch for as auto-stitching ships

Multi-floor auto-stitching is the single most-requested feature in the Ritn3D support inbox. Target ship date: late 2026. When it lands (from Ritn3D or a competitor), expect the good implementations to do all three things:

• Automatic alignment — walls between floors snap to the same grid.
• Correct stairwell handling — voids cut cleanly, upper floor doesn't cap the stair space.
• Story-selection UI — walk floor 1 with floor 2 faded, or vice versa; switch between them with one click.

The bad implementations will do just the first (auto-stack, no stairwell logic) and market it as "multi-floor support." When you see a claim, verify with an actual two-story plan and a stairwell before subscribing.

Related

• How to convert a floor plan to a 3D model
• Best AI floor plan to 3D tools in 2026
• 3D printable floor plan STL export guide

Written from first-hand experience benchmarking Ritn3D and every competitor against multi-story inputs. If you're stuck on a two- or three-story conversion and neither pattern above works for your setup, email me through the contact form — I use these cases to prioritize the auto-stitching feature roadmap.