Hot Box construction guide

Hot Box Construction Guide Tools needed:     

Screwgun Square 2 1/2" Hole saw l/2" Drill bit l/8" Drill bit (for pre-drilling)

Materials and Measurements: You should use a Square to mark-off your cuts. Be careful to cut straight and true. Do not rush this step or your container will not be square.     

22 - 2"x 10" boards at 42" long for the Top, Bottom, and Sides.

4 - 2"x 10" boards at 38 1/4" long for the removable Front slats.

4 - 2"x 4" boards at 36 l/2" long for the Front and Rear Interior Braces.

1 - 2"x 4" board at 42" for the Horizontal Front Support Brace.

2 - 2"x 4" boards at 34 1/2" for the Vertical Front Support Braces.

Construction Tips: All boards are fastened with 2 1/2" Phillips head screws. Use all purpose or galvanized screws for this job. Do not use sheetrock screws. You will need a power Screwgun to fasten these screws. If you have access to an electrical source nearby, a 3/8" standard drill with a screwdriver attachment will work well. A cordless Screwgun is a very handy tool for this job if you don't have any power source.

If you are using standard 2" x 10" wood lumber, "pre-drilling" your screw holes with a l/8" drill bit is highly recommended so you don't strip the screw heads. However, if you are using Recycled Plastic Lumber, no predrilling is necessary. Remember, 2" x 10" lumber is actually l l/2" x 9 l/4".

If you have no access to a Screwgun, you can try nailing with 2 l/2" nails (#8d galvanized). However, bins built using this technique will not be as strong or last as long.

You should try to have at least 3 people for this job. The more people you have the easier it is to support the boards during construction. This is especially important to make the box square, and when it is necessary to move the box around (it will get very heavy when completed) you may also want to divide into groups to handle the different tasks.

Important Note: If you are using plastic lumber the shavings from sawing the boards are toxic and contain fiberglass. Make sure you wear gloves and a dust mask! Carefully collect the shavings and dispose of them. Use a drop-cloth under your cutting area to make clean-up easy.

Construction Plans

Step 1 Vertical Sides (You will need to make 2 of these) Lay 4 - 42" boards on a flat surface. (Use two extra boards underneath if your working surface is irregular). Be careful to line-up these boards so the ends are flush and square.

Place the Rear Interior Brace (2"x 4"x 36 l/2") along one end of the 4 boards. Make sure this board is flush and square. You can use another board to assist in this. Make sure there are no gaps in your 2" x 10" 's. Fasten with 2 1/2" screws. Use 2-3 screws per board.

Place the Front Interior Brace (2" x 4" x 36 l/2") along the other end of the 4 boards. Recess this board 1 3/4". Make sure there are no gaps in your 2" x l0" 's. Fasten with 2 l/2" screws. Use 2-3 screws per board.

Repeat Step 1 for Side #2 Step 2 Back Side Lift Side #1 upright with the 2" x l0" 's running vertically so you can fasten from the top down. Have l -2 persons hold in place as perpendicular as possible to your working surface. If you have extra hands available lift Side #2 upright as well. Remember you will be working from the Rear of the container now so the two sides with the "Rear Interior Braces" should be facing you and on the inside of the container.

Place the 1st 2" x 10" x 42" board on top of the sides. It is very important that you line-up and square this board to the sides. The corners should be flush. Fasten the first Screw on the lower right corner. Then fasten the top part of the board after making sure you are square. This technique allows you to adjust your square before adding more screws. Repeat this process on the left side. The Container should stand up on its own now. Now add the remaining 3 boards to complete the Rear Side. Again, make sure the Container is square and flush. You can then fasten an additional 2 screws on each end of each board for strength.

Step 3 Bottom Flip the Container over on its Top (Imagine that the Top is now facing down ) Lay-out 5 2"x 10"x 42" boards on the side-rails running the same direction as the Rear Side. These boards will only fit flush one way! Squareup and flush starting from the Rear of the container and proceed to fasten boards with 2 screws at each end. Be careful to line up these screws so you don't miss the board underneath! Again, pay special attention that there are no gaps as you fasten all four bottom boards. You may need to stretch-out the front end for a flush fit. The last board will overlap so don't be alarmed.

Step 4 Front Flip the container right-side-up with the Front Side facing you. Place the Front Support Brace horizontally at the top of the front face. Fasten one end first with two screws. You may need to stretch the two sides so the Front Support Brace will fit flush at each end. Fasten the other end with two screws.

Attach the external Vertical Front Support Braces. Make sure to let the overhang go to the center of the Container. This creates the groove for the Front Slats.

Step 5 Removable Front Slats You will need to drill three 2 1/2" holes in 2 - 2" x 10" x 38" boards. You must use a power drill for this; it can be done "off-site" if necessary. Use a sharp hole saw bit and take your time. Make your first hole exactly in the center of the board (both horizontally and vertically). You may need to drill halfway through one side and then drill from the other side to complete the hole.

Measure 8" from each end and mark in the center of the board. Proceed to drill out these remaining two holes.

Repeat steps for second board.

Slide 1st board with holes down the groove inside the front. Then slide a board without holes; continue to alternate boards until closed. You are now ready to LOAD! Step 6 Top Simply lay 4 - 2" x 10"x 42" across the Top. Do not fasten for easy removal and temperature readings.

Step 7 Aeration Cut 6 - 48" lengths of 2" PVC Pipe.

Drill 1/2" holes every 2 1/2" for internal aeration. Leave the last 8" of each Pipe without holes.

You may want to attach an internal brace inside of the rear wall for the upper layer of Pipes so they remain level.

Note: Carefully clean-up plastic shavings.

Step 8 Loading Container Place a 2" layer of hay or woodchips on the floor. This will help absorb any extra moisture or food waste seepage.

Insert lower the layer of 2" pipes into the container.

Load Compostables. (A 50/50 mixture of carbon and nitrogen materials which may include: food waste, manure, woodchip, lawn clippings, leaves, etc.). You will also need to add some inert organic material such as finished compost or soil as a "starter". Mix materials well and fill up to the level of the second layer of pipes.

Water evenly so mix is moist to slightly wet.

Insert second layer of Pipes into the Container. Rest on the optional rear brace so the pipes remain level and don't get shifted during loading and natural settling.

Continue loading mixture up to the last 8"-12" from the top.

Load a 4"-8" layer of finished Compost or soil for the "Bio-filter". This will help minimize the odor as well as convert the ammonia gases into usable nitrogen. Check the temperature daily. You should reach approximately 90° within 3 days and 120° within approximately 5 days if your mix is good. If not, remix and check moisture levels. A successful batch should reach 120°-145° for 2-3 weeks and then drop-off slowly over 2 weeks. If the temperature climbs over 150°, adjust the amount of air by plugging tubes. The temperature may "crash" quickly if the bacteria within the desired heat range heat up too much. Unload finished COMPOST into a shallow curing bin or pile.