DIY Kiln for Wood Drying

Build a structure that is sized appropriately for the dimensions and amount of lumber that you will be drying. To dry 250 to 300 board feet of 16 foot lumber simultaneously, you will need a shed that is about six feet wide, 18 feet long and seven feet tall.

Construct a foundation that will hold the shed. It doesn't need to be too fancy. You can pour a concrete slab, lay beams on concrete blocks and mount joists on the beams or install concrete pillars to build a wooden floor frame.

Design the roof so that it is facing due south if you are in the northern hemisphere and due north if you are in the southern hemisphere. The angle of the roof should be roughly equal to your latitude. Near the border between Canada and the United States, a 45 degree angle works fine.

Sheath the roof with glass or corrugated polycarbonate of the kind used in greenhouses. Glass is more expensive but will look nicer. Salvaged windows work fine if you can fit them together to create a tight roof.

Cut four vents in the north wall of the kiln, one in each corner, each about one foot square. Fit the vents with screens to keep animals out and doors that can be closed and latched to regulate air flow.

Insulate the walls well with batt insulation or rigid foam. You can also experiment with greener alternatives such as packed straw or walls built out of cob. Sheath the insides of the walls with plywood and paint it flat black for maximum heat absorption.

Install two fans at the peak where the north wall meets the roof, and aim them down the slant of the roof. These fans will blow the hot air down through the lumber and out the vents at the bottom.

Put an access door into one of the sides of the kiln or into the north wall. If you fashion the entire north wall as an opening door that can swing up and out of the way, it will be easier to get lumber into and out of the kiln.