I passed by the red Space Invader that can be seen on the main image of this guide almost daily for a couple of years. Every time I saw it, it inspired me to make something similar. However, I never did. The months passed and eventually I was about to move out from this city as I was headed to Africa to cycle around the continent. I had only a few weeks left and had not forgotten about my mosaic daydreams. Realizing it was now or never, I started planning the projects I wanted to exhibit in the city before my departure.
I settled on reproducing key local landmarks: lighthouses (don’t ask me why, but I have a soft spot for them), the ferry that crosses the estuary, early 20th-century villas that face the coast…
I tried to find online tutorials for creating and installing mosaic street art while preparing for this project, but they were very hard to locate. I am sharing my experimental results with the hope that they may be useful to others. Of course, this is by no means a definitive guide. I don’t know if the methods that I’ve used were the most appropriate, as the most important question remains unanswered: will the mosaics that I installed withstand the test of time?
Obligatory disclaimer: sticking stuff to your city’s walls is probably illegal. I’m not your mom or your lawyer. Do what you want at your own risk.
Putty Knife / Spatula: for spreading the adhesive evenly through the mesh and applying grout into the joints.
Sponge & Water Bucket: For wiping away excess grout from the face of the tiles during application.
Flexible rubber squeegee: to spread the grout.
Mixing Container & Stirrer: To blend the grout powder with water to the correct consistency.
Protective Sheet / Baking Paper: A non-stick work surface to lay under the mesh while applying the backing layer.
Bill of Materials
Small square tiles – 1cm in my case (I tried 5mm but it was very finicky). Glass tiles are the most homogeneous in terms of dimensions. Porcelain tiles ended up closer to 9.25mm and had more imperfections.
Fiberglass Mesh Filet: the flexible backing sheet holding the pixel pattern in place during assembly.
White PVA Glue: to adhere the tiles to the mesh.
Soudal Fix All High Tack (or equivalent): adhesive used as the flexible weather-proof structural membrane on the back of the panel, and for final mounting to the outdoor wall.
Exterior C2-Grade Thinset Mortar: an exterior cement thinset suitable for non-porous tiles, used to form a durable backing that holds the tiles together.
Exterior CG2-Grade Cement Grout: powder grout designed for filling exterior tile joints.
Make sure that the model photo was cropped to the precise outline of the building and opened it with Aseprite.
Set the Sprite Size to twice the desired tile grid count. This higher resolution lets you offset tiles by half-square increments to create staggered rows. This lowers the reference image’s resolution to match your planned mosaic scale, giving you a pixelated template you can easily draw right on top of.
Create a new Layer above your reference image. This is where you will draw your pixel art.
Build and load a color palette based on your supplier’s available tile colors so your design reflects the exact materials you’ll be using.
In View > Grid > Grid Settings, set the grid size to 2×2 pixels.
Set the Brush Size to 2px.
Draw your design using your color palette. Tip: Use the Symmetry Tool to speed up the process if your building or motif has repeating elements.
Use File > Save Copy As to save the final result as a .png.
For the next step, I used Illustrator to create a visible grid and print the template to scale.
Here is the process:
Import the .png image to a blank A4 or US Letter Artboard.
In the Properties of the image, resize it to match the actual target dimensions of your mosaic
Select the Rectangular Grid Tool, click on the Artboard, and set the grid dimensions to match your mosaic size.Set the number of Horizontal Dividers to Vertical Tiles − 1, and the Vertical Dividers to Horizontal Tiles − 1
Align the grid with the image and printthe template.
Gluing the tiles to the fibreglass mesh
Protect the paper template by gluing a transparent plastic film over it to prevent tiles from adhering to the paper (I used a regular stick of glue for that purpose). Place your fiberglass mesh over the plastic, then tape all layers down securely to your work table using masking tape.
Position tiles starting from the top down to prevent accidental shifting. Secure each tile with a single, tiny dot of white PVA glue on the mesh.
Avoid flooding the backs of the tiles so your structural adhesive can still bond directly to them.
Let dry for 24 hours, peel off the plastic backing, and trim excess mesh with an X-Acto knife.
Applying thinset to the back
Is it necessary to apply a thinset backing layer to your mosaic?
Having tried both methods, I don’t have a definitive answer. While I personally favor using a thinset backing, both approaches are viable depending on your needs. Here are the main advantages and disadvantages of each option:
Direct Mesh (No Thinset Backing)
Pre-Fab Thinset Backing
Preparation
Faster: Skips an extra prep step.
Requires extra prep: Mixing and leveling thinset takes time and effort to get flat.
Transport
Flexible & Durable: Easy to carry without risk of cracking.
Rigid & Fragile: Requires careful handling during transport.
Wall Requirements
Versatile: Conforms to uneven masonry, rough walls, or curved surfaces.
Flat Surfaces Only: Needs a flat wall, as rigid edges won’t adapt to surface bumps.
On-Site Installation
Stressful: Requires applying adhesive to every single tile quickly before it cures – tricky for late-night installations.
Fast & Easy: High-tack adhesive applies in a few quick spots rather than full coverage.
Grouting
Not possible prior to installation: Grout will leak through the open mesh backing during street mounting.
Possible in the workshop: Provides a solid, sealed base so you can grout prior to mounting.
Mix the thinset per the package instructions. To keep application clean, mix it directly inside a Ziploc bag, then cut off a corner to use it as a makeshift piping bag.
Mortar dust is nasty so you should use proper PPE during that step (N95 or P100 respirator, gloves and safety glasses ideally).
As for the target consistency, you don’t want your thinset to be too runny or it will leak through the gaps between the tiles.
Pipe the thinset onto the back of the tiles, then use a spatula to spread it evenly to a 4mm thickness. Apply firm downward pressure while spreading to ensure the thinset bonds thoroughly with the rear surface of each tile.
Let it firm up for 1 to 2 hours (depending on ambient room temperature). Once it holds its shape, trim away any squeeze-out around the perimeter using an X-Acto knife or the edge of your spatula.
Finally leave it to dry for 24 to 48h. Don’t touch it before that or it will crack! Personally that was the most difficult part as I always wanted to check on it so I ended up putting my pieces out of view during that time.
About the drying process:
Curling caused by uneven drying is a common challenge with thinset backing. Because the edges lose moisture faster than the center, differential shrinkage pulls the perimeter upward.
While covering the piece with a plastic sheet to slow evaporation and applying a flat, weighted board once it reaches a firm set helps mitigate curling, there isn’t a single foolproof fix. Reader advice and alternative tips on preventing thinset curling are welcome in the comments!
Applying grout
Similarly to the last step comes the question: to grout or not to grout?
I have tested both options. At times, I left the mosaic ungrouted simply because I liked the raw look – though laziness likely played a role too. Choosing whether to grout often came down to color: since I only had one grout color, I preferred using it when it created a strong contrast against the surrounding tiles.
As with the thinset, mix the grout in a Ziploc bag and pipe it onto the mosaic. Keep the consistency slightly more liquid than the thinset so it flows easily between the tiles.
After piping, use a rubber squeegee to spread the grout and press it into the spaces between the tiles.
Allow it to harden for 10 to 20 minutes, then use a damp sponge to clean the excess off the tile surfaces.
Out of curiosity, I used thinset to grout some of my mosaics. On the left is standard grout; on the right is thinset.
Neither was significantly harder to apply than the other, but grout has a much finer particulate size. As a result, the thinset finish looks noticeably coarser.
This is an example of one of the mosaics that I chose to leave as-is without applying any grout.
Gluing the mosaic outdoors
When transporting mosaics with a thinset backing, wrap them in cardboard to protect them. Unbacked mosaics on mesh can simply be rolled up and placed in your bag.
For the adhesive cartridge, cut a large notch at the tip to allow the material to flow quickly. if you can find grey adhesive, it will blend much better with concrete if it happens to squeeze out from the sides of the mosaic.
Once at the final location, apply a generous amount of adhesive to the back of the mosaic. Press it against the wall and wiggle it slightly to spread the adhesive evenly. Apply firm pressure across the entire surface, then admire your work!
Final result
I hope that you found this guide useful. As I said, I’m in no way an expert and I would love some pointers if some of you happened to come across the same issues that I encountered and found ways to solve them.
I’ll leave you with the photos of the creations that I had time to disseminate in my city before my departure as well as the buildings that inspired them.
Cheers!
Footnotes
The following online content provided some assistance and/or inspiration during the making of this project:
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Making-of
Mosaic Pixel Street Art: a How-to Guide
I passed by the red Space Invader that can be seen on the main image of this guide almost daily for a couple of years. Every time I saw it, it inspired me to make something similar. However, I never did. The months passed and eventually I was about to move out from this city as I was headed to Africa to cycle around the continent. I had only a few weeks left and had not forgotten about my mosaic daydreams. Realizing it was now or never, I started planning the projects I wanted to exhibit in the city before my departure.
I settled on reproducing key local landmarks: lighthouses (don’t ask me why, but I have a soft spot for them), the ferry that crosses the estuary, early 20th-century villas that face the coast…
I tried to find online tutorials for creating and installing mosaic street art while preparing for this project, but they were very hard to locate. I am sharing my experimental results with the hope that they may be useful to others. Of course, this is by no means a definitive guide. I don’t know if the methods that I’ve used were the most appropriate, as the most important question remains unanswered: will the mosaics that I installed withstand the test of time?
Obligatory disclaimer: sticking stuff to your city’s walls is probably illegal. I’m not your mom or your lawyer. Do what you want at your own risk.
Requirements
Tools
Bill of Materials
Walk-through
Designing the mosaic
I used Aseprite to convert photos of target buildings into pixel art designs. Here’s the install file for Windows.
Here is the step-by-step process I followed:
For the next step, I used Illustrator to create a visible grid and print the template to scale.
Here is the process:
Vertical Tiles − 1, and the Vertical Dividers toHorizontal Tiles − 1Gluing the tiles to the fibreglass mesh
Protect the paper template by gluing a transparent plastic film over it to prevent tiles from adhering to the paper (I used a regular stick of glue for that purpose). Place your fiberglass mesh over the plastic, then tape all layers down securely to your work table using masking tape.
Position tiles starting from the top down to prevent accidental shifting. Secure each tile with a single, tiny dot of white PVA glue on the mesh.
Avoid flooding the backs of the tiles so your structural adhesive can still bond directly to them.
Let dry for 24 hours, peel off the plastic backing, and trim excess mesh with an X-Acto knife.
Applying thinset to the back
Is it necessary to apply a thinset backing layer to your mosaic?
Having tried both methods, I don’t have a definitive answer. While I personally favor using a thinset backing, both approaches are viable depending on your needs. Here are the main advantages and disadvantages of each option:
Mix the thinset per the package instructions. To keep application clean, mix it directly inside a Ziploc bag, then cut off a corner to use it as a makeshift piping bag.
Mortar dust is nasty so you should use proper PPE during that step (N95 or P100 respirator, gloves and safety glasses ideally).
As for the target consistency, you don’t want your thinset to be too runny or it will leak through the gaps between the tiles.
Pipe the thinset onto the back of the tiles, then use a spatula to spread it evenly to a 4mm thickness. Apply firm downward pressure while spreading to ensure the thinset bonds thoroughly with the rear surface of each tile.
Let it firm up for 1 to 2 hours (depending on ambient room temperature). Once it holds its shape, trim away any squeeze-out around the perimeter using an X-Acto knife or the edge of your spatula.
Finally leave it to dry for 24 to 48h. Don’t touch it before that or it will crack! Personally that was the most difficult part as I always wanted to check on it so I ended up putting my pieces out of view during that time.
About the drying process:
Curling caused by uneven drying is a common challenge with thinset backing. Because the edges lose moisture faster than the center, differential shrinkage pulls the perimeter upward.
While covering the piece with a plastic sheet to slow evaporation and applying a flat, weighted board once it reaches a firm set helps mitigate curling, there isn’t a single foolproof fix. Reader advice and alternative tips on preventing thinset curling are welcome in the comments!
Applying grout
Similarly to the last step comes the question: to grout or not to grout?
I have tested both options. At times, I left the mosaic ungrouted simply because I liked the raw look – though laziness likely played a role too. Choosing whether to grout often came down to color: since I only had one grout color, I preferred using it when it created a strong contrast against the surrounding tiles.
As with the thinset, mix the grout in a Ziploc bag and pipe it onto the mosaic. Keep the consistency slightly more liquid than the thinset so it flows easily between the tiles.
After piping, use a rubber squeegee to spread the grout and press it into the spaces between the tiles.
Allow it to harden for 10 to 20 minutes, then use a damp sponge to clean the excess off the tile surfaces.
Out of curiosity, I used thinset to grout some of my mosaics. On the left is standard grout; on the right is thinset.
Neither was significantly harder to apply than the other, but grout has a much finer particulate size. As a result, the thinset finish looks noticeably coarser.
This is an example of one of the mosaics that I chose to leave as-is without applying any grout.
Gluing the mosaic outdoors
When transporting mosaics with a thinset backing, wrap them in cardboard to protect them. Unbacked mosaics on mesh can simply be rolled up and placed in your bag.
For the adhesive cartridge, cut a large notch at the tip to allow the material to flow quickly. if you can find grey adhesive, it will blend much better with concrete if it happens to squeeze out from the sides of the mosaic.
Once at the final location, apply a generous amount of adhesive to the back of the mosaic. Press it against the wall and wiggle it slightly to spread the adhesive evenly. Apply firm pressure across the entire surface, then admire your work!
Final result
I hope that you found this guide useful. As I said, I’m in no way an expert and I would love some pointers if some of you happened to come across the same issues that I encountered and found ways to solve them.
I’ll leave you with the photos of the creations that I had time to disseminate in my city before my departure as well as the buildings that inspired them.
Cheers!
Footnotes
The following online content provided some assistance and/or inspiration during the making of this project: