How to Make a Firebox for a Maple Evaporator

Locate an open area for the firebox. You need to be away from trees, buildings and other flammable objects.

Dry fit the concrete blocks to make a square with one open end, which is where you will add wood to the fire. Do not use mortar at this point. Doing a dry fit allows you to verify that everything will fit together the way you expect it to. Generally, the firebox should be four concrete blocks long by three blocks wide and four blocks high.

Line the open box with the firebricks. The firebricks keep the concrete blocks from being damaged by the fire. Leave an opening in the third row of the back of the box for the flue to set through.

Place the evaporator on top of the mocked-up firebox. The rim of the evaporator should rest on the top edge of the box. Make any needed adjustments to your design so that the evaporator fits perfectly atop the firebox.

Remove the evaporator and take apart the firebox, down to the bottom row of blocks. Use mortar to attach the next row of blocks on top of the first row. Spread the mortar on the blocks where they meet, using a trowel as if icing a cake. Stagger the blocks so that the box is as strong as possible. Continue with the subsequent rows, remembering to leave the flue opening in the third row.

Line the box with the firebricks, mortaring them to the concrete blocks as well as to each other. Let dry completely.

Insert the flue into the flue opening. Attach the flue pipe to the flue, following the manufacturer's directions. The height of the flue pipe is up to you, but longer is better. The pipe should be tall enough so that ash does not land in the evaporator.

Lean the sheet metal piece across the open end of the firebox to keep drafts from putting out the fire or stirring up too much ash. Insert the evaporator and you are ready to cook.