18 February 2002

Using Foam Core to Construct a Room Box, Part I

George Hoffman

Foam Core is a sheet material that is composed of an inner core of foam with an outer covering of high quality paper. It is available in thickness from 1/8 - 1 inch and may be purchased in art supply stores. In this forum we will offer a technique to enable you to use foam core in room box construction and avoid the most common problem, warping.

Storing Foam Core

To prevent damage during storage we suggest that it be wrapped with brown kraft paper and placed between two sheets of plywood and stored in a vertical or horizontal position.

Foam Core Assets:

• Easy to cut with an X-Acto knife
  
• Bends easily
  
• Glues well with vinyl and cyanoacrylate glues
  
• Paint and gesso adhere well
  
• It is light weight
  
• Low in cost

Disadvantages:

• Dents and scuffs easily
  
• Warps easily

Gator Board*, a hard surfaced sheet material, 3/4" thick is used as a base for this room box. Maple flooring strips are glued to the Gator Board using tinted vinyl glue. Once the flooring is in place apply weights to hold the flooring in position until the glue is dry. We recommend allowing 24 hours for the drying period. Next the floor is sanded and the finish applied. When the floor finish is thoroughly dry, cut the 1/4" Foam Core to the size required for your room. Make any corner bends. Lay the Foam Core flat again and mark out your window and door openings and cut them out. Cut pine studs–-we generally cut these 3/4" by 1-1/2" to accommodate our deep Shaker style windows as seen above. The Foam Core walls may now be cemented along the perimeter of the flooring base using a gap filling cyanoacrylate glue. To hasten the drying period an accelerant such as "Zip Kicker ®” may be added. Glue the prepared pine studding to the outer edge of the flooring base and the back of the Foam Core walls as shown in the photos below. Use care here to be clear enough of the window and door openings to prevent the blocks from being viewed from within the room itself. Once the walls are in place you may install the Foam Core ceiling. If you will be applying a gesso or paint to the walls and ceilings do this now.

Windows and doors can now be applied.

The photo above shows hard wiring inserted through the pine studs from the bulbs then to the switch box. Wiring may be run easily now and routed over the ceiling to the switch box as shown in the left corner of photo. We generally have several circuits that allow for lighting options within the room box. The top outer sheathing of the room box is plywood secured by screws and this allows easy access for maintenance of the wiring and for bulb replacement. The transformer remains outside room box to reduce interior heat build up.

When all walls, studs, accessories and wiring are completely set apply a 1/4" birch plywood outer sheathing. This may be finished in any way you choose. To complete the box, attach a picture frame with glass onto the front.

* Gator Board; What is it ?

• It is a lightweight structural panel consisting of a rigid polystyrene foam core. It is surfaced on both sides by a smooth moisture resistant wood fiber veneer.
  
• The surfaces are excellent for applying gesso or paint.
  
• The standard surface is bleached white hard veneer.
  
• The board does not require any special preparation prior to painting, Acrylics, water based enamels, oil and solvent based lacquers will all perform well.
  
• Use caution to keep solvent based paint from contacting open foam ends
  
• Cutting; We find straight cuts are best performed on a circular table saw using a fine plywood blade moving slowly past blade to reduce chipping of hard surface.
  
• Curves and irregular shapes are best cut using a band saw, although with patience hand type saws can be used.