Foam core is a wide, flat piece of extruded foam with a piece of thick poster board glued to either side. The material has become a popular medium for creating scale models of buildings in architecture and scenery for miniature games such as Warhammer and Dungeons & Dragons. Foam core boards are inexpensive and can be cut and glued into a variety of shapes.
Draw several sketches of the model from various angles. These sketches should give you a rough idea of the general dimensions and shape of the model. Pay careful attention to large flat areas like walls or ceilings.
Purchase single-color foam core boards. The number of boards necessary will depend on the size and shape of the model. Use your sketches to estimate the amount of foam board necessary for the project.
Deconstruct the model into individual pieces. Draw each piece to scale on a piece of paper and cut the shape out to create a template.
Place the template on the foam core board and use a pen or marker to trace the edge of the template.
Slice the shape out of the foam core board using a utility or hobby knife. Slice the foam board three times, cutting a third of the foam with each slice. Cut slowly to ensure a smooth edge.
Assemble the foam pieces together and glue the edges. Generic white glue works well, but adhesives like PVA will provide a stronger hold. Avoid any glues with solvents or heat which can degrade the foam into harsh chemicals. Insert pins or tacks into the foam to hold the pieces in place while the glue dries.
Remove the pins and tacks. Cover all exposed foam with a coat of PVA or water-based paint. This will prevent the solvents in the primer or paint from disintegrating the foam and reducing the structural strength of the model. Seams and exposed foam can also be covered with tape.
Spray the model with a coat or two of spray primer. Popular primer colors are black and white because they provide the best base for paints.
Paint the model and add any necessary accessories or materials.
A rabbet can be constructed for a cornered seam between two right-angled pieces. Mark the width of the foam core board on the corner edge. Cut and remove one layer of paper and the foam but leave the second paper intact. The paper will be glued onto the foam edge of the opposite wall to hide the foam edge and create the corner seam. Objects with geometric shapes like hexagons and octagons can be made by cutting a mitre, or angled edge, on the side of the foam core. This will prevent exterior gaps when the edges are placed together. Remove portions of the paper and foam to create a textured look. Remember to cover all exposed foam before priming or painting.