How to make a 3D printed house number sign

To make a 3D printed house number sign, design a plate with large, bold, high-contrast digits — at least about 100 mm (4 inches) tall so they read from the street — print it in a UV-resistant filament like ASA or PETG, and hang it on hidden keyhole slots so no screws show. Here's how to size it, design it, print it and mount it.

Step 1 — Size the digits for the street

A house number has one job: be readable from a car or by a delivery driver at a glance. Many local codes in the US follow the International Fire Code rule for address numbers: at least 4 inches (102 mm) tall, with a stroke at least ½ inch (12.7 mm) wide, in a color that contrasts with the background, and placed where it's visible from the street. Rules differ by city and HOA, so check yours — but those numbers are a good minimum anywhere. If the house sits far back from the road, go bigger.

Step 2 — Pick a bold font

Thin and script fonts disappear at a distance. Choose a heavy, simple typeface — a bold sans or a slab — so each digit has a thick stroke and clear open shapes. Avoid fonts where 1 and 7, or 6 and 8, look alike.

Step 3 — Design the sign

You can lay out a sign in any CAD program if you have the time, but I used the 3DGEN nameplate generator — type the number and the print-ready plate appears in seconds in the browser, no CAD.

1. Type the house number — digits and letters both work (for example 24B).
2. Choose a bold font such as Bungee, Alfa Slab One or DejaVu Sans.
3. Set the digit height. Text width sets how tall the lettering is across the plate (up to 100 mm); use Scale (up to 300%) to go larger. Aim for digits of 102 mm or more.
4. Raise the digits. Use Relief so the numbers stand off the plate — raised digits catch light and shadow, which helps them read from an angle.
5. Frame it. Turn on the Border for a finished look, and set the plate's Thickness, Margin and Corner radius.
6. Choose contrasting colors for the digits, base and border — white on black, black on white, or brass-gold on dark grey.
7. Add the mount. Set the mount to Hidden keyhole (wall mount) — one keyhole for a short plate, two for a long one — and set Screw head to the diameter of your screw heads. The keyholes sit in the back, so nothing shows from the front.

Check that the plate fits your printer bed. A long number at full size can approach the bed's limits; if it doesn't fit, print each digit as its own plate and mount them in a row.

Step 4 — Choose an outdoor filament

A house sign lives in sun, rain and frost, which rules out the usual indoor choice:

• ASA — the most UV-stable of the common filaments and the most heat tolerant (a heat-deflection range of roughly 90–110 °C). The best pick for a sign in direct sun.
• PETG — a good middle option: tough, moisture tolerant, softens around 70–90 °C, and ages slowly in the sun.
• PLA — avoid for a sunny wall. It's the weakest in UV and softens around 50–60 °C, which a dark sign in summer sun can reach. Fine only in a shaded, covered porch.

Darker colors run hotter in the sun — another reason to use ASA for a dark plate.

Step 5 — Print it in two colors

The digits sit on top of the plate, so you can print a two-color sign without a multi-material printer: change filament at the first layer of the digits and the numbers come out in the second color. With a multi-material printer, export the 3MF — the plate and digits are separate objects, so you just assign a filament to each. Print the plate flat with a few extra walls for a stiff, weatherproof part.

Step 6 — Mount it

1. Hold the sign in place and mark the keyhole positions on the wall — measure them off the printed plate.
2. Drill and plug the wall with anchors suited to the surface (brick, render, wood).
3. Drive the screws in, leaving the heads standing out just enough to slip into the keyholes.
4. Hang the sign by sliding the keyholes down over the screw heads, and check it with a level.

Mount it near the front door or on a post by the driveway, at eye level and away from where plants or a porch light will hide it.

Troubleshooting

• The numbers are hard to read from the street: make them taller, use a bolder font, or increase the color contrast.
• The sign warped in summer: it was printed in PLA, or a dark plate got very hot. Reprint in ASA.
• The color has faded: UV aging — ASA holds color best outdoors.
• The sign wobbles on the wall: use two keyholes for a long plate and set the screw heads to the same depth.

FAQ

How big should house numbers be?

A common minimum is 4 inches (102 mm) tall with a stroke at least ½ inch wide and good contrast. Check local rules — and go bigger if the house is set back from the road.

What's the best filament for an outdoor sign?

ASA, for UV resistance and heat tolerance. PETG works too; PLA is only for shaded, covered spots.

Can I hide the screws?

Yes — the hidden keyhole mount puts the slots on the back, so the sign hangs on screw heads with nothing visible from the front.