Building a cold smoker for smoking trout

I have always liked smoked trout, wondered how it is prepared and not come across a cold smoker before. When I started fly fishing a couple of years ago I developed the taste for trout which now features often in our cookery at home.

So, looking for a project to work on during the early 2021 COVID lockdown, I decided to build my own cold smoker. This blog post goes through how I did the build. See other posts for the testing and my views on the end product!

Smoker design

I did a bit of research online and read several articles from those who have built their own smoker. Some of these were using old fridges, filing cabinets and wine crates. I wanted to do something in wood as I enjoy building things this way.

My smoker is a variation on a tall slim wooden box. It uses the ProQ cold smoke generator, which burns sawdust, as a smoke source.  Dimensions of the smoker are 1.3m high at the front, 1.1m high at the back.  The width and depth are based on the size of the racks I used.

I had some large stainless steel racks from a previous shelving system and decided to cut two of these in half with an angle grinder to make four shelves 35 x 46 cm. Therefore the design and sizing of my smoker was built around these four shelves. Design sketches I did while thinking through how I was going to build it are below.

Materials

I have built my smoker out of new planed wood purchased from the local builders merchants. If you are using reclaimed or scrap wood, make sure it’s clean and hasn’t been treated with any toxic wood preservatives.

The structure is assembled from 25mm section timber and covered with tongue-and-groove cladding. I have used 25mm deep T&G but a thinner material would also be fine.

What I used to make the smoker:

  • The ProQ smoke generator and a few bags of wood dust
  • Two steel racks, cut in half
  • Approx 12m of square timber
  • Approx 24m of 25mm x 115mm tongue-and-groove cladding board
  • Plywood for the large door
  • Catches for the doors
  • Ventilation hole covers

Building the smoker

First, build the frames for each side.  I planned the correct size by laying out the wood with the shelves I had made by cutting two larger shelves in half.

Each side frame will look something like this. Secure the horizontal timbers with long wood screws.

Next cover the sides with cladding going from floor level all the way to the top of the frame, including the sections at the top which are needed to create a sloping roof.  

I glued the tongue and groove for extra stability and to get a good smoke seal.  You could equally use plywood to clad the box.  I used panel pins to secure the cladding to the frame.

Cut the slope top once the side cladding is complete.

When two sides are done, use the shelves to find the correct width so that the cross members can be fitted.

Assemble the smoker box

I used six cross members to create the carcass. The two in the middle will be a shelf support.

Check the shelves fit ok and allow some room for the wood to swell up slightly when it is outdoors.

Detail of the top showing the gentle slope for water run off. Check that the whole thing is square and solid.

Now it is time to clad the back.

I glued each board and made the box with an overhang which I cut off at the end to make the sides neat.

The main box is finished and is very solid. The rear overhang will be cut off at the right angle for the roof.

Fitting the smoker shelves

The middle shelf will sit on the wooden cross members but the other three shelves will need supports. I fitted small angle brackets for this.

The shelves I am using have a round end due to the unit they came from. I adjusted the height of the brackets to take account of this and still keep the shelves level.

Now all the shelves fit well, I can get on with the next stage. This photo shows the smoker in the bottom tray – all looking good!

Finishing and painting

I painted a first coat of blue wood stain on the body and then build a roof from more T&G timber, glued together. I will varnish the top so it keeps the natural wood.

The inside of the smoker will not be painted, and I hope that with time, exposure to smoke should provide a good seal to these surfaces.

Detail of the top, screwed down into the timber and sealed with glue. I have left a small gap at the front to allow the smoke to escape and generate airflow.

I then created two 25mm holes on each side, top and bottom, to be the main air intake and smoke escape points. I had read that a good flow of smoke is important.

At this stage I gave the smoker two more coats of the blue wood stain.

Smoker doors

I want the whole front of the smoker box to be removable, in two sections – a large top section to allow me to load and unload the smoker racks and hooks, and a small bottom strip to allow management and monitoring of the smoke generator without letting all the smoke escape from the box during use.

To create this I added two external cross beams, seen in the photo above. I then created a small bottom door, varnished it and added a handle and side clips.

Next I used a piece of 18mm plywood to create the main door. It was varnished on the outside and edges and fitted with a handle.

These small metal covers make the ventilation holes look nicer. Found them on eBay.

I bought these pull catches to close the doors with. They are adjustable to keep good pressure on the doors, stopping smoke escaping around the edges.

A final check of the sealing inside and it is almost finished!

I found a grill pan which fits across the bottom frame for the smoker to live in. This raises it off the ground slightly and brings the smoker in line with the air intake holes.

And it is finished!

I am hoping that the large plywood door will keep the smoke in and be easy to maintain. It has had three coats of yacht varnish for weather protection.

Next steps

On the patio, ready for the test run!

Thanks for reading, I will post more about the test smoke and the smoked trout results shortly.