Foam Board

Foam board is a classic material for architects, modellers and students: it’s lightweight and flat, and all you need to cut it is a craft knife and steel ruler. Build architectural massing models, contour terrain, diorama house walls and doll’s house roomboxes. White board has a white core and black board has a black core. Both come in 3 and 5 mm thicknesses; white self-adhesive board is available in 5 and 10 mm for mounting prints. Find out how to combine foam board with plastic and EVA foam on our page about diorama and model making materials.

Foam board for models, dioramas and crafts

Architectural models

Build a white massing model of a city block at 1 : 200 or 1 : 500 scale, a study model of a house at 1 : 100 scale, or a contour model of a plot. For contour models, each layer represents one height interval: 5 mm board at 1 : 200 scale represents 1 m of terrain. At 1 : 100 scale, cut the walls from 5 mm board and the interior partitions from 3 mm board.

Pick: Choose white 5 mm foam board, 70 × 100 cm for walls and solid forms, and white 3 mm foam board for partitions and contour layers.

Dioramas, gaming terrain and model railways

Cut walls for houses, ruins and bunkers for miniatures, station buildings, retaining walls and low-relief buildings for a railway backdrop. The “remove the foam, leave the paper” joint (see below) hides the foam edge at corners. Black board suits dark scenes and display boxes for a miniature or diorama, where a light-coloured edge would stand out.

Pick: Choose 5 mm for walls for 28 mm miniatures and 3 mm for 15 mm miniatures. For dark walls, use black 5 mm foam board, 25 × 35 cm or black 3 mm foam board.

Doll’s houses and roomboxes

For a 1 : 12 scale roombox, 10 mm board gives the walls realistic thickness and rigidity, so use it for the walls and floor. Cut furniture carcasses, shelves and platforms from 3 mm board. Join the corners with PVA glue and hold them in place with pins while the glue dries.

Pick: Choose white self-adhesive 10 mm foam board or 5 mm board for walls and floors, and 3 mm board for furniture.

School and presentations

Make a project display panel, a three-panel freestanding board for a competition, a model of a historic building or a boxed ecosystem diorama. Make a three-panel board from one 70 × 100 cm sheet using V-grooves for a neat fold without joining two pieces.

Pick: Choose white 5 mm board, 70 × 100 cm, for a display panel. To mount a print, use white self-adhesive 5 mm foam board, 50 × 70 cm.

Photography and video

White board reflects light and softens shadows; black board acts as a flag, deepening shadows and adding contrast. Join two 70 × 100 cm boards along a long edge with tape to make a folding V-flat that you can stand beside a product or model. Smaller boards work as backdrops and side panels for tabletop photography.

Pick: For a V-flat and flags, use black 5 mm foam board, 70 × 100 cm and a white 5 mm board in the same size.

Art and framing

Mount a photograph, poster or print for an exhibition, use the board as a lightweight backing in a frame, or paint studies on it in poster paint or acrylics. Standard foam board is not archival and is not suitable for conservation framing. When painting a large area, paint the back as well, or the board may warp.

Pick: For mounting a print, choose white self-adhesive 5 mm board; for frame backing, white 3 or 5 mm board.

Foam board: which thickness and colour to choose

How to cut foam board straight and square

Every model starts with a clean cut. Use a sharp blade at a low angle, making several light passes instead of one forceful cut.

You will need:

cutting mat · steel ruler · craft knife (snap-off blade knife) with a new blade · set square · soft pencil · fine sandpaper on a sanding block

1. Mark the cut line with a soft pencil, not a pen – ink may show through the paint later.
2. Place the board on a cutting mat and put the steel ruler against the side you want to keep. If the knife slips, it will cut into the waste, not your piece.
3. Guide the blade at a low angle to the board, but hold the knife perpendicular to its surface so the edge is square. A sharp blade at a low angle slices the foam instead of tearing it.
4. With the first light pass, cut through only the top paper layer; with the second, cut through the foam core; with the third, cut through the bottom paper. Don’t press hard to cut through everything at once.
5. Hold the ruler with your fingers spread out and away from the blade’s path, and pull the knife away from your body.
6. If the knife starts catching or the edge is ragged, snap off a fresh blade segment.
7. Check the right angle with a set square and smooth small imperfections with fine sandpaper on a sanding block.

How to make neat wall corners: remove the foam, leave the paper

This joint hides the foam edge and makes the corner look like one piece. It works well for buildings in architectural models, diorama houses and boxes.

You will need:

cutting mat · steel ruler · craft knife (snap-off blade knife) · offcut of board to use as a depth gauge · PVA glue · dressmaking pins · masking tape · set square

1. Cut out the walls. Add one board thickness to the length of the wall that will overlap the adjoining wall at the corner (5 mm for 5 mm board).
2. At the overlapping end, cut through only the top paper layer, one board thickness from the edge. Use an offcut of board as a guide.
3. Cut out the foam between the cut and the edge with the blade held flat; leave the outer paper intact. It’s better to make several shallow cuts than one deep cut.
4. Scrape foam residue off the paper with the back of the blade or a fingernail.
5. Apply a thin line of PVA glue to the exposed foam on the adjoining wall and fold the paper flap over it. The foam edge disappears and the corner is neat.
6. While the glue dries, secure the corner with pins through the paper into the foam and masking tape; check it is 90° with a set square.
7. Add the roof or floor only after the glue has fully dried, following its instructions.

How to cut a V-groove for a neat 90° fold

Use a V-groove to fold one sheet into a three-panel display, box or wall corner. The bottom paper layer acts as a hinge.

Tips for accurate foam board work

• The blade is a consumable: snap off a fresh segment after a few long cuts. A blunt blade crushes and tears the foam.
• Measure all matching walls from the same edge and cut them in one batch so they’re the same size.
• Dressmaking pins work as clamps while PVA glue dries and can stay in the joint as hidden dowels.
• For windows in walls, pierce the corners of the opening first or cut from the corners towards the centre to avoid cutting past them.
• To make a curved wall, cut parallel grooves into the inside through the paper and into the foam (for 5 mm board, start with 3–5 mm spacing), then bend the board around a bottle or tube. Don’t cut through the outer paper; heat won’t help with bending.
• Before painting, seal exposed foam edges with PVA glue or acrylic gesso so the paint doesn’t soak in unevenly.
• 10 mm board holds drawing pins, so you can make a pinboard for inspiration or pinned prototypes.
• Before cutting EVA foam or plastic, make a template or test model from foam board – you’ll spot mistakes before cutting into your final material.

Handling and storing foam board

Store foam board flat and horizontal in a dry, clean indoor space – not upright, rolled, in a damp cellar or in direct sunlight. Heat damages the core, so don’t leave it by a radiator or in a hot car. Carry large sheets by two edges: a dented corner or crushed foam won’t spring back. The paper layers absorb moisture, so board finished on only one side will warp. If a board bends, lay it flat under a weight, but it’s better to prevent it from bending in the first place. Keep the release liner on self-adhesive board until you’re ready to use it, and protect the adhesive side from dust.

Frequently asked questions

How do you cut foam board without ragged edges?

Use a new craft-knife blade at a low angle and make 2–3 light passes, guided by a steel ruler on a cutting mat. A ragged edge almost always means the blade is blunt – snap off a fresh segment.

What glue should you use on foam board?

For strong, neat joints, use PVA (white glue); for quick assembly, use a low-temperature glue gun. Pins will hold the pieces while the glue dries. Solvent-based adhesives may damage the foam, so test any other glue on an offcut first. Find suitable adhesives in our range of craft glues.

Can you paint foam board?

Yes, with water-based paints such as acrylics, gouache or poster paint. Paint both sides of a large area to stop the board warping. Solvent-based sprays may damage the foam, so test them on an offcut first.

What thickness of foam board should you choose for an architectural model?

3 mm for 1 : 200 and 1 : 500 scales and interior partitions; 5 mm for walls at 1 : 100 scale; 10 mm for bases, 1 : 50 models and 1 : 12 roomboxes. The 10 mm thickness is available as white self-adhesive board.

How do you mount a photo on self-adhesive foam board?

Leave the board slightly larger than the photo. Peel back 2–3 cm of the release liner along the top edge, position the print, then slowly pull away the liner and smooth from the centre towards the edges in short sections. You can adjust the position for about 5 minutes; full adhesion takes about 24 hours under an even weight. Trim the edges afterwards with a new blade.

What is the difference between white and black foam board?

Black board also has a black core, so the cut edge stays black and doesn’t need painting. It’s suitable for frames, display boxes, dark scenes and photography flags; white board is useful for models, panels and reflectors.

Is foam board suitable for outdoor use?

Not for long-term use: the paper layers absorb moisture and the board will warp. For outdoor projects, choose foamed PVC sheet or aluminium composite panels.