How to Build a Reverse Flow Offset Smoker




In this Instructable I'm going to show you the basic steps for making a smoker. Specifically a Reverse Flow Offset Smoker. What is an Reverse Flow Offset Smoker you ask, it basically has the firebox off to the side of cooking chamber with a steel baffle plate that keeps the direct heat off of the meat. This allows the meat to be bathed in the smoke and keeps direct heat off the meaty goodness.

The parts for this build are from a combination from recycled and new metal. The biggest expense will be the steel to build the firebox as you want to use thick steel. You want to use thick steel is it will keep the temperature stable and easy to maintain. I used 1/4" mild steel plate for the firebox and baffle plate and had the steel shop cut it to size for me with their brake. It takes them seconds to do it so if you don't get it cut to size be prepared to be really good cutting with a mini-grinder. The smokers you buy at Walmart or the hardware store will typically be of thin steel.and you will have a hard time maintaining the temperature, although they do work if you only smoke a few times a year.

This smoker is a beast, not sure what the total weight is but it is heavy, so it should retain heat well.

You will need a welder for this build, wire feed or stick, if you have a welder you probably already know how to weld. If not this project can be a fun way to learn, although it is outside the scope of this Instructable.

The Parts Required:

  • Cooking Chamber (Old Air Tanks, Water Tanks, Expansion Tanks, Make your own etc..)
  • Firebox
  • Baffle Plate
  • Angle Iron for Frame
  • Casters
  • Vents (some bolts and sheet metal)
  • Smoke Stack
  • Thermometer
  • Hinges
  • Expanded Metal for Fire Basket and Cooking Grate
  • Wooden Handle (Aluminum and wood)
  • Shelf
  • High Heat Paint

Tools Required:

  • Welder
  • Mini-Grinder (with Grinding and Cutting Discs)
  • Pliers
  • Chipping Hammer
  • Wire Brush
  • Safety Equipment (Welding Shield, Gloves, Safety Glasses, Face Shield)

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Step 1: Video Overview

Here is a video overview of the build, I will add instructions on the following steps.

Step 2: Body of Cooking Chamber

In my build I used an old expansion tank from a boiler. You can use what ever you want, be creative, just keep in mind that you just need a place for the meat to rest so smoke and meat can move over it. I welded on some legs to make a frame and some casters to the frame so the whole thing will roll.

An opening was cut into the tank and the piece of metal was saved and used for the door. Hinges were welded on the cooking chamber door and then bolted to the cooking chamber. Also some aluminum stock was screwed around the opening so the "door" has a place to sit and so a gasket could be added so no smoke escapes. I used some pure cotton as a gasket since a smoker doesn't get very hot but you can use felt or silicone.

Step 3: Firebox Build

I sized the firebox by using the following website to size my firebox

I made sure to oversize it a bit so I wouldn't have a problem maintaining the temperature during a cook. As mentioned in the intro, the firebox is made from 1/4" plate steel, so it's heavy but will evenly distribute heat and keep stable temperature. I kept it simple by making a square box and welded on some sturdy hinges for the door. On the side I drilled holes for air intake and welded on a bolt so a vent control could be added. The vent control is nothing more than some sheet metal. The handle for the door of the firebox is from a chipping hammer, simple, cheap and effective. The latching mechanism was just some scrap metal welded in place on the side of the box and a bar bolted to the door with some washers and the handle from a chipping hammer welded into place.

Because the firebox is so heavy it is really hard to move around or store should the need arise. I solved this by making the firebox removable by bolting on the firebox to the body of the smoker. This was accomplished by welding a plate on the body of the smoker and then matching the firebox to the plate. You can see how this was done in the video and pics.

Step 4: Baffle Plate and Cooking Grate

Unfortunately I don't have any good pics of the baffle plate but you can kinda see it in this picture. It is the plate steel that is in the body of the smoker, it keeps the direct heat away from the food, acts as a heat sink and provides radiant heat. It extends most of the length of the cooking chamber and is welded in place. So the smoke and heat leaves the firebox, goes under the baffle plate come redirects back towards the firebox but since the baffle plate is there it exits via the chimney. Google how a baffle works in the context for a smoker to get a better idea and the video also covers this.

Also I don't have any pics of the cooking grates except some pics with some food cooking that you can see at the last step. But it is straight forward to weld in some angle iron so the cooking grate can sit on and cut a piece of expanded mesh to use as a cooking surface.

Step 5: ​Chimney

So the heat and smoke needs a place to go so. The chimney is made from a 4" ventilation pipe. A flange was fabricated and chimney attached.

Step 6: Final Touches and Fire Basket

Thermometers were installed and a fire basket was built using expanded mesh. The fire basket is where the hot coals will sit. Also some aluminum was used to make brackets to mount a wooden handle on the door of the cook chamber.

Wash the smoker inside and out, you want to get rid of any left over flux from welding and paint the smoker with some high heat paint.

Step 7: Test Cooking

Fire up the smoker the first time let it get up to temperature and let it burn off any oils. Then you can start smoking! Here I did some short ribs, they came out awesome!

Some tips use charcoal as your fuel and wood as your smoke. If you try to burn just wood, you will need to let it burn down to coals first then add more wood for the smoke. Takes practice but it is worth it!

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    12 Discussions

    Filou turg

    Question 6 months ago on Step 3

    What is the size of the firebox?

    Teslas brother

    3 years ago

    I love this ible! It's beautiful and looks FUN! I am determined to attempt it.

    I have viewed many smoker ibles and I am shocked that I have yet to see someone, ANYONE, mention being concerned with the toxic paints, different alloys(comments below DID mention galvanized though(finally someone!) and I am not one who trusts it to be burned away with high heat) or metal composites/combinations when using heat to cook our own FOOD! Science has even made us aware of the chemical reaction from using aluminum cooking pots/pans with certain foods and heat or other facts about leeching toxins into our food and I understand this is not aluminum but aluminum isn't the only concern.

    I have old water tanks and air compressor tanks but, hesitant to use them. Am I being overly concerned? If so, Why?

    Am I a rare example of being concerned with this issue or am I just unfamiliar with the few dangers there are?

    Literally no concerns at all? or just too excited about the final project to care???

    I speak from science teaching us to be concerned with leeching and chemical reactions but, also from ignorance not negativeness or cockiness.

    I'm looking forward to some responses and thank you!


    3 years ago

    An old hooded gas BBQ makes a good smoker, just need to seal up back and underneath. They have all the shelves built in.

    Then old computer cases make good fire boxes, rip the guts out and any plastic trim.

    Sawdust and wood shavings from the workshop for the smoke. all for free.


    4 years ago

    Be sure you DO NOT use galvanized tanks for this. They give off toxic zinc fumes when heated.

    1 reply

    Reply 3 years ago

    Only for the first burn, get it hot, real hot. The black oily layer seals the steel after that.


    4 years ago

    Putting the door in can be eased a bit if you cut the side whee the hinges go completely and useing 1/4 inch black pipe , cut the pipe almost through and weld it to the one side where you want hinges, keeping the cut side of the pipe down...after its welded you can finish the other three sides of the door, and slip a bolt through the pipe, cut the last bit of bolt through and your hinges are perfectly aligned.


    4 years ago

    Great job.

    Wish I could find a tank that sized. looks like its perfect for a single rack of ribs.

    5 replies

    Reply 4 years ago

    junk yards, metal recycling places or garbage dump will have tanks.

    I'll be uploading my smoker this coming summer. I'm using a 400 gal. tank found at my local metal recycling, cost me only $40.00.


    Reply 4 years ago

    Yeah I have some 10 and 30 gallon water tanks, and a few air tanks sitting behind the shop. I'm actually in process of building a 100 gallon air tank into a reverse flow on a trailer. I have it about 90% done and have spent $56 so far. Small tanks shaped how I want are like unicorn horns around my area.


    Reply 4 years ago

    give me your unicorn list if you like (size, shape of tanks), tag me here for emailing.

    I could send photos of the tanks with cost and shipping to you if you like.


    Reply 4 years ago

    Old hot water heaters of 40 gallon size is what you need. I was looking for a hot water heater several years back and was able to come up with them quite easily.


    Reply 4 years ago

    Speak to you local plumber. The older geysers are that size.