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How do I design an architectural model for 3D printing?

By Terry Tan

Updated

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A white filament-printed concept model of a colonnaded building around a triangular courtyard, its wings, roofs and courtyard floor printed as separate sections

An architectural model for filament printing (fused deposition modeling, FDM) needs every detail that must show at least 1 mm thick at model scale, and walls of 1.2 mm (2.0 mm where it is handled or glued). The file must be a closed, watertight solid, and a building bigger than the printer is split by floor or wing. This guide shows how to check that at your scale, prepare the file from SketchUp, Rhino or Revit, then orient, split and finish the building, using models from our Singapore studio. Or hand the whole model to the Additive Inn scale model team.

Wall thickness and details at model scale

Shrinking a building shrinks every wall, frame and rail with it, and the printer has a limit. It builds in fine lines of melted plastic, so a detail thinner than 1 mm on the model drops out or prints as one wobbly strand.

The sum: real size in millimetres, divided by the scale number, is the size on the model. A 200 mm wall at 1:100 becomes 2 mm and prints. A 50 mm door frame at 1:100 becomes 0.5 mm, half the minimum, and at 1:200 it is 0.25 mm.

Diagram of the same doorway in a 2 mm wall at 1:100, twice. Marked wrong, scaled as it is: the 50 mm door frame becomes 0.5 mm. Marked right, drawn up to 1 mm: the frame now prints. A note says a 200 mm wall becomes 2 mm and prints as it is.
At 1:100 the wall is 2 mm and prints, but a 50 mm door frame is 0.5 mm, so draw it at 1 mm.

The minimums for a 3D printed scale model in filament:

  • Smallest detail: 1 mm at model scale. A mullion (the bar between window panes), a balcony rail or a door frame has to be at least 1 mm thick on the model to print.
  • Walls: 1.2 mm, and 2.0 mm on anything handled, glued or lifted off: the base, a removable floor, a column glued in.
  • Openings: at least 2.0 mm across for windows and doors.
  • Signage: strokes of 1.0 mm and letters 5 mm tall read at arm’s length.

Exaggerate, don’t drop. Thicken a detail to 1 mm rather than leave it true to scale or delete it. From viewing distance a door frame drawn a little heavy still reads as a door frame; a facade with its frames missing reads as a blank wall.

Long, thin uprights are the hardest case. Railing posts and slender columns printed standing up wobble as the nozzle works on them, so thicken them to at least 1 mm, or print a railing as a flat panel and fit it afterwards.

Front of a cream filament-printed heritage building model under an orange tiled roof, its columns and two storeys of balcony railings printed crisp and even
Columns and balcony rails thickened just enough to print cleanly on one of our heritage building models.

Kept thick enough, fine architecture prints well in filament: the colonnade, arched windows and entrance below are all part of one of our concept models.

Side view of a white filament-printed building model: a long colonnade of slender columns under a wall of paired arched windows and a central arched entrance
Columns, arched windows and an arched entrance, printed in filament (see the model).

Thin walls, sagging overhangs and the other defects that can hit any filament print are in FDM print defects that start in the design, and every process’s figures sit side by side in the design rules table.

Upload it and a person checks fine detail

Choosing a scale for an architectural model

Scale trades the size of the model against the smallest detail it can carry. Pick the scale at which the smallest detail that matters is still 1 mm thick, or plan to thicken it.

The scales below are the ones architects typically use for each job, a common starting point rather than a rule. Your brief or your display space may call for another.

ScaleTypically used for1 mm on the model is (real)
1:50Interiors50 mm
1:100One building100 mm
1:200A block200 mm
1:400 or 1:500A site400 to 500 mm
1:1000A masterplan1 m

The last column is the thinnest real feature that survives at that scale without being thickened. At 1:100, a 100 mm mullion just prints; at 1:500, nothing thinner than half a metre does, so a site model shows massing, not window frames.

Size counts too. At 1:100, 36 m of building is 360 mm of model, the most our desktop printers take in one piece. Our large-format printer takes up to 1000 x 1000 x 1200 mm, and anything bigger is split (see below).

Close view of a golf course scale model: green fairways, pale gravel bunkers, grey paths and tiny pin flags on the greens
Our Mandai Golf Course model was built at 1:400 so the whole course sat on one base (see the project).

Not sure of the scale? Tell us the site

Preparing the file from SketchUp, Rhino or Revit

The most common problem in an architect’s file is a wall with no thickness. SketchUp faces, Rhino surfaces and many Revit exports describe a wall as a single sheet: it looks solid on screen, but a printer cannot print a sheet. Give every wall real thickness, 1.2 mm or more at model scale, before anything else.

Diagram of the same wall drawn twice. Marked wrong, a single surface with no thickness; seen end on it is a single line, 0 mm. Marked right, a closed shell; seen end on it is a hatched section with real thickness.
A wall drawn as one sheet has nothing to print; give it thickness and close it all round.

The model also has to be watertight: closed all round, like a balloon with no holes, so the slicer (the software that turns a model into printer moves) can tell inside from outside. Why a 3D file won’t slice shows how to find and close holes, and the file checklist covers each check in one line.

  • SketchUp: make each part a solid group or component, and delete stray lines and doubled faces inside walls.
  • Rhino: join each part into a closed polysurface, and check it shows no naked edges (edges left open, a sign of a gap) before you export.
  • Revit: export the massing and the facade you want to show; leave out furniture, pipes, ducts and anything hidden inside.
  • Interiors: delete what nobody will see, unless a floor lifts off to show it. Hidden detail only makes the file bigger and slower to check.
  • Export: STL, 3MF, OBJ, STEP or IGES, in millimetres. Native files (.skp, .3dm, .rvt) are exported first. Say the scale in the quote notes.

The instant quote takes uploads up to 1 GB, and email works for files under 25 MB. Formats, units and export resolution are covered in full in how to export and send a 3D file.

File ready? Upload it for an instant price

Orienting a building model on the print bed

How a piece lies on the print bed decides how strong it is and which faces come out cleanest.

  • Floor slabs and bases lie flat, their largest flat face on the bed, so they print without supports and stay flat.
  • Loose columns lie down. A filament print is weakest between its layers, so a thin column printed standing up can snap along a layer. Lying down, every layer runs its full length. Print it on its side, cut flat along its underside so it sits on the bed, and glue it in.
  • Overhangs within 45° of vertical. An overhang is any face that leans out over nothing. Past 45° it needs supports (temporary props printed under it), which leave marks. A 45° chamfer (a sloped underside) under a balcony or an eave lets it carry itself: overhangs and support marks has the detail.
  • Show faces up or to the side, away from the bed and the supports. Tell us in the quote notes which elevation matters most.
Diagram of the same slender model column printed two ways. Marked wrong, printed standing up: it snaps along one layer. Marked right, printed lying down and cut flat underneath, so it sits on the bed along its whole length; its layers run its full length and it holds.
Stood up, a thin column breaks between two layers; laid down, each layer runs the whole column.

Unsure how it should lie? Ask us to check the orientation

Splitting a building into floors and wings

We split a model where it is bigger than the printer, or where a split makes painting and assembly easier. One piece can be up to a 360 mm cube on our desktop printers and 1000 x 1000 x 1200 mm on our large-format printer.

  • Split along lines the building already has: a floor slab, the junction between wings, a roofline, a facade panel edge or a change of colour or material. The join then hides in a line the eye expects.
  • Not through a show face. A cut across the middle of a plain wall leaves a seam nobody can explain.
  • Floors that lift off show the layout inside. Split by floor and they stack back like the real building.
  • Pegs and sockets keep the pieces in line: leave 0.2 mm each side so a peg pushes in without forcing. Splitting and joining large 3D prints has the other joints.
Diagram in two parts. Left: a three-storey building model in three pieces, one per floor, the top floor lifting off small pegs on the floor below, labelled split by floor. Right: a cut-through of one peg sitting in its socket in the floor above, with a 0.2 mm gap each side.
Split by floor, with pegs that leave 0.2 mm each side, the floors lift off and drop back in line.

We recommend where to split and explain why; the decision is always yours. Send the model whole and ask us to split it, or send it in pieces.

Top view of a white filament-printed courtyard building model: each wing and roof is a separate section and the courtyard floor is four panels, the joins visible as fine lines
Each wing, roof and courtyard panel of this concept model is its own section, joined on the building's lines (see the model).

Pegs and sockets must fit? Ask us to check the joints

Joining and finishing the model

A peg lines the pieces up; glue holds them. Two-part epoxy suits a joint that never opens. A floor meant to lift off stays unglued and sits on its pegs.

Left raw white, a massing model shows its joins as fine lines, like the courtyard model above, which suits a concept model read for form. For a presentation piece the seams are filled and sanded, then the model is primed and painted. A matte finish usually reads as more architectural than gloss. Filling and sanding shows what that process can and cannot hide, and 3D print finishing options compares the paints and clear coats.

Colour can also be printed in rather than painted on: our Interasia ship model was printed in the line’s red, white and navy filament. Choosing colours for a 3D print covers what each route suits. If you would rather hand over drawings than a file, how architectural scale models are made walks through every stage from print to lit base.

A 3D printed site cabin from a construction diorama, painted teal with cream window frames, a green bicycle and a grey cabinet beside it
Printed, then hand-painted
The deck of a container ship model stacked with containers printed in red, white and navy filament, on a navy nameplate base
Colour printed in filament

Presentation model? Ask us which finish suits it

When to switch to resin (stereolithography, SLA)

Some detail cannot be thickened to 1 mm without looking wrong: ornament, grilles, fine railings, sculpted fittings. Print those in resin, which builds details down to 0.5 mm with a smoother surface that needs less filling before paint.

  • Detail: 0.5 mm, walls 1.0 mm, against 1 mm and 1.2 mm in filament.
  • Size: one resin piece can be up to 1700 x 800 x 600 mm.
  • Mixed builds: many models print the massing in filament and the fine parts in resin, then paint them to match.
  • Hollow parts need drain holes: resin print defects explains where they go.

How resin is priced is on pricing, and the process on our resin printing service.

Close view of two white model immigration gates numbered 1 and 2, with grey caps, red cross signals, fine speaker grilles and red and blue trim, glass panels between them over a lit walkway
Our ICA gate model was printed in resin for the smooth, moulded look of the real gates, down to the speaker grilles (see the project).

Fine facade detail? Ask whether resin suits it

Frequently asked

How do I design an architectural model for 3D printing?

Keep every detail that must show at least 1 mm thick at model scale, walls at 1.2 mm (2.0 mm where the model is handled or glued), and the file a closed, watertight solid. Then lay floor slabs flat on the print bed, lie loose columns down, and split a building bigger than the printer by floor or wing, with pegs that leave 0.2 mm each side so the pieces line up.

What scale should I use for a 3D printed architectural model?

Pick the scale at which your smallest detail that matters is still 1 mm thick, or thicken that detail to 1 mm. Typical choices, not fixed rules, are 1:50 for interiors, 1:100 for a single building, 1:200 for a block, 1:400 or 1:500 for a site and 1:1000 for a masterplan. Our Mandai Golf Course model was built at 1:400 so the whole course sat on one base.

How thin can walls be in a 3D printed architectural model?

Walls should be at least 1.2 mm thick at model scale, and 2.0 mm on anything handled, glued or lifted off, such as a base, a removable floor or a column glued in. Smaller details such as mullions and rails can go down to 1 mm. Window and door openings should be at least 2.0 mm across.

How do I stop windows, railings and mullions disappearing at small scale?

Thicken windows, railings and mullions to 1 mm at model scale instead of leaving them true to scale or dropping them. A 50 mm door frame at 1:100 is only 0.5 mm, too thin to print, but drawn at 1 mm it prints and still reads as a door frame from viewing distance. If a detail cannot be thickened without looking wrong, print that part in resin.

How do I turn a SketchUp, Rhino or Revit model into a printable file?

Before you export from SketchUp, Rhino or Revit, give every wall real thickness: a face or surface with no thickness cannot be printed. Then make each part a closed solid (a solid group in SketchUp, a closed polysurface in Rhino), strip furniture and services you will not see, and export STL, 3MF, OBJ, STEP or IGES in millimetres. Our instant quote takes uploads up to 1 GB.

How do I split a building model into parts, and how big can each part be?

Split a building model where it is bigger than the printer, or where a split makes painting and assembly easier: along a floor, between wings, at a roofline or a facade panel edge. One piece can be up to a 360 mm cube on our desktop printers and 1000 x 1000 x 1200 mm on the large-format one. We recommend where to split and why; the decision is always yours.

How do I join the floors and sections of a building model?

Join the floors and sections of a building model with pegs and sockets that leave 0.2 mm each side, so the pieces line up by themselves. Glue them with two-part epoxy for a joint that never opens, or leave a floor unglued so it lifts off to show the interior. Seams placed on a floor line or a panel edge disappear once the model is filled and painted.

How should I orient a building model on the print bed?

Floor slabs and bases lie flat on the print bed, and loose columns lie down. A filament print is weakest between its layers, so a thin column printed standing up can snap along a layer, while lying down every layer runs its full length. Keep overhangs within 45° of vertical, or put a 45° chamfer under balconies and eaves.

When should I use resin instead of filament for an architectural model?

Use resin (stereolithography, SLA) for detail that cannot be thickened to 1 mm without looking wrong, such as ornament, grilles and fine railings. Resin holds details down to 0.5 mm with a smoother surface, and one resin piece can be up to 1700 x 800 x 600 mm. Many models print the massing in filament and the fine parts in resin.

Can you check my file, or build the whole model for me?

Yes, a person checks every uploaded file before it prints and flags details under 1 mm, walls with no thickness and parts too big to print in one piece, and suggests where to split. If you would rather hand it over, our scale model team works from your drawings and designs, prints, paints, bases and lights the whole model.

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