How To Build A Mushroom Fruiting Chamber

I’ve not written recently so I’ll start by saying happy new year to you all! I hope 2021 is an improvement on 2020 for you. For me, 2020 was a great year ironically, in my personal life I bought my first house and got promoted in my day job.

With the new house came a new space to expand. Subsequently all my free time has been devoted to getting the Mushroom Empire up and running. The house came with an extremely large detached double garage which is where the empire will be.

I started by removing the sauna that was left by the previous owners. This had the added bonus of paying for some of the fruiting chamber that would take its place. Once disassembled and sold the sauna left 2 things for me to deal with, one good, one bad. The good was a high-rated power cable that ran the sauna’s massive 8kw element, perfect for the steriliser I am going to build.

The bad was the tiles which needed to come up as they were ugly and in the wrong place. Owing to the garage construction, the FC would need to slot between 2 brick columns. I removed the tiles and tile cement then painted the floor.

As with everything I build I tried, tested and costed it all on the computer program, Sketchup, first. Because I was limited to the space between the columns for the FC I costed the best material to use as a frame. The material I chose was 63*38*2400 CLS timber. This length for this space meant wasted offcuts would be minimalised.

I considered installing a drain in the floor, however, it would have cost another £200 in plumbing parts and timber as well as adding a layer of complexity to the build to get the right fall, not something I fancied. I opted to ‘tank’ the floor and just use a wet-vac to clean it. The framing was fairly straight forward stud style walls and flooring.  Something worth noting is that I decided to drill holes in all the floor studs. This will allow for air to flow under the floor and prevent condensation from causing problems down the line.

I framed it out and with the help of a friend, installed and stood up the walls and ceiling. Once secured I dropped in the 18mm OSB floor. I chose OSB because it’s relatively inexpensive and thanks to the adhesive it’s manufactured with it’s strong and kind of waterproof.

Next up was insulation, I chose polystyrene because it’s inexpensive and readily available. However, it makes a huge mess when you’re installing it and it breaks easily. If you can afford it, use Kingspan.

I cut the polystyrene inserts oversize, so they fit snug and wedged in between the studs, I then sealed up the gaps with some aluminium ducting tape. The garage semi-insulates the FC anyway, but I decided to add insulation, so it was more efficient in the summer and winter.

I cut an oversize hole out of the back of the FC between the two studs for my exhaust fan. I drilled through the garage wall an made up a frame that holds the fan secure.

I spent a lot of time going over the best material for my FC’s walls and ceiling. It had to be waterproof, cleanable, hard wearing and long lasting. My searches ranged from bathroom tiles, to lino and simply poly-sheeting, in the end I went for sheets of Corex plastic.  I chose 4mm because it was inexpensive, easy to cut and install on your own. I felt going any thicker wouldn’t provide any additional benefit vs cost increase. I decided to hang it with some roofing screws and a clear flexible cap. These may have been overkill but they did help distribute the load that the screw applies, so it doesn’t crush down into the corex and pull through.

Next, I sealed the seams between the corex with some white silicone. I did a rather bad job of this, next time I would space them further and infill the gap with silicone.

I cut a hole above the door to fit the misting system duct through and secured it to the ceiling using duct clips. I used 100mm Manrose ducting throughout the misting system. It’s big, easy to clean and relatively cheap. My advice is to seal the joints up with silicone where regular access isn’t required as this isn’t watertight ducting. I would also suggest making a slight fall in the ducting. This way water that condenses in the duct will collect at a single point and can be drained out periodically rather then pooling sporadically. For more information on the misting system, I’ll have a separate post up on it and how I made it.

I added a couple of 6500k, 4000lm waterproof LED lights and passed them through the ceiling with some plastic cable glands.

I then tanked the floor making it waterproof. I chose to use safety flooring as it’s thicker than regular lino, harder wearing and doesn’t tear as easily during installation. I did explore other methods of waterproofing the floor using tiles or other lino, but they didn’t cost much less. The fact that this flooring style goes up the wall means cleaning is much easier. I put in cove formers and caps with mastic grab adhesive then loosely laid the flooring out. I then made mitre cuts in each corner, massively failing at that. I then cut the other half of the floor, since the rolls come in 2m widths, and using spray adhesive, glued them down. I cut the lino to the right height and tucked it into the cap portion of the cap and coving

I stuffed a load of silicone in the mitre corners that I made to hide my terrible work and then sealed the join between the two floors. When done right cap and coving can look seamless, when done by me there is nothing but seams.

I then made an access panel for the exhaust fan and added foam tape to keep it watertight before securing it over the fan and covering the hole.

I then framed up a door which I covered, again, in corex plastic. To make sure the door was airtight, I then ran a strip of PVC around the perimeter of the door frame and added some foam tape (not shown in photo) to seal it.

Finally I added a window and 2 toggle clamps to keep the door shut

As I said before, I’ll go into more detail about the misting system, lighting, racking and exhausts in another post exclusively for them. This post was simply how I built the chamber. The final cost omits the cost of labour (since it was all me), tools and the above items since you may be able to source cheaper/different misters, lighting and racking that will save money.

The actual chamber itself, however, is probably going to cost roughly the same for everyone. You may wonder why I didn’t just use a tent. If this was a temporary setup I would have. Tents are great, inexpensive, and relatively reliable. They will leak humidity however; the frame will begin to rust from the inside out, they don’t have insulation and they’re more difficult to clean.

Frame

CLS 2400*38*68
Floor – 14 Lengths
Ceiling – 14 Lengths
L, R & Back – 24 Lengths
Front – 12 Lengths
Total = £188.16

Screws 2*100mm Boxes
Total = £10.58

Hinges
2 Packs
Total = £8.98

Door Toggle Catch
1 Pack
Total = £7.99

Walls & Ceiling

Polystyrene – 10 sheets
Total = £40.70

Aluminium Ducting Tape – 2 Rolls
Total  = £13.00

Corex Plastic – 10 Sheets
Total = £99.96

Roofing Screws – 6 Packs
Total = £17.94

White Silicone – 4 Tubes
Total = £13.96

Floor

18mm OSB – 2 Boards
Total = £42.00

Screws – 1*40mm boxes
Total = £4.99

Capping – 5 Lengths
Total = £18.75

Coving – 5 Lengths
Total = £18.00

Safety Flooring – 10sqm
Total = £88.00

Gripfill Grab Adhesive – 2 Tubes
Total = £4.98

Spray Adhesive – 2 Cans
Total = £7.98

Total for delivery on heavier items = £66.00

Grand Total = £651.87

Please note, prices I’ve linked may change because of inflation, Brexit and Covid over the years! I hope you found this post informative, keep an eye out for my posts that talk about humidity, fresh air exchange, lighting, racking and temperature controls!

As always, if you have any questions feel free to comment below or drop me an email!

Stay safe in 2021!

Gareth