Cold frame project

My recent project to build a cold frame. Ordered the aluminium cold frame and then started thinking about how and where it was going to go. I could have just placed it directly on the floor and it would be done in a day, but disadvantages are; being low down, it inevitably gets shaded by something, it gets splashed by rain bouncing off the floor, it’s a pain bending down to look into it and not easliy accessible. Also, raising it, allows the area underneath to be used for overwintering plants and keeping them dry. Raising it up is where all the work and fun begins.

To increase the interior height, I ordered 3 levels of a raised bed. These come with 6 pieces of wood to make the construction. I had to discard these and made my own long ones to elevate the frame. I had 50mm square machined down and then screwed on 35mm square to make a section for the floor to sit on. At the bottom of the legs, I screwed in 6" hot dipped special galvanised bolts to make adjustable feet, screwed in coated with silicone grease.

Construction of the raised bed wood and legs proved very tricky, as getting everything level, straight and square when you have no starting point is fun. The answer is to do every stage slowly, methodically and check at every tightening.

Stainless screws screws used throughout the whole project and this is where using No.12 instead of the usual No.10 helps. They grip better and the head is more firm on the surface.

Every joints had to be absolutely perfect. If it was 1mm out, I’d plane down or reject the piece and cut it again. I didn’t want any piece pulling in or forcing out the construction.

The distance between the cross struts needs to be this, as even 19mm ply sags if the gap was much larger.

All the wood used in the project has been treated with 3 coats of Ronseal multipurpose wood treatment, with all ends being soaked for 3 hours each. Then follwed by 4 coats of clear Barrettine decking oil.

Level, level and level again and make all feet have the same pressure.

Fitted auto louvre. Polished the aluminium and wiped every piece with camellia oil.

Made these end pieces to cover water ingression and it looks prettier. Ribbed wood gives nice finishing touch.

The floor is marine grade 19mm ply treated with Ronseal multipurpose wood treatment followed by 2-part flexible epoxy boat paint. This was trickier than I had imagined. Once mixed, you have about 30 mins to apply, but as it’s very thick, it’s a slow process and difficult. It’s literally like painting on Araldite. Then it takes days to dry properly on the surface, so you have a 6’x4’ sheet of plywood that you can’t touch and need to keep dry, upright and dust free. Pain.

Added strengthening struts. The whole structure doesn’t move at all when pushed.

Added draught excluder underneath

…and made aluminium angle brackets to add excluder inside at the frame junction. All bolted on in case need to remove.

…and between glass using 9mm siliconised fibres on the best 3M 9448 Adhesive backing.

Added velour to the glass partitions to stop scratching each other when they slide.

Painted piston white to improve temperature measurement on the auto louvre.

Putting a circulation fan inside. Tried another fan that got good reviews and it was absolute junk. That’s reviews for you. This Blauberg has been excellent up to now. Cut some pvc tube and made this rivetted aluminium bracket to house it.

The fan is plugged into a wifi plug device that allows me to adjust the speed from my phone in 1 % increments. This is great to adjust the ideal amount of breeze.

Made this polystyrene housing for the temp/humidity guage. It connects via wifi to my phone and is set to alert me if temp goes over 35c and also allows me to follow the stats on a graph.

It’s all to house a collection of rare carnivorous plants. The machining of the wood legs at the start, allows 6 x 24" square trays to be fitted to within a few mm. I changed the aluminium shelf brackets by making deeper ones. This makes the shelf slighly more rigid.


Good opportunity to take a break now. We’ll all recommence in 45 mins for a question/answers session.


Wow !


Wow !


Fantastic work!


Wow again. Fantastic result :ok_hand:



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Oh come on………can you just fit me into your build schedule………just lovely, so envious at your skills👍


Thanks Gazza, but I don’t think there’s any special skills here. What I would say is it took me a lot of patience and discipline not to rush it, stick my plants inside and enjoy looking at them bathed in sun. 3-4 weeks work, on off. It gave me time to source various things like decent screws, waterproof paint, different draught excluders, bolts, temp gauge, wifi dimmer, fan, etc…doing this type of post actually logs things for myself, so I can look back on in years to come if need be and maybe someone can pick up an idea or product from it.

One more point I forgot. The end corner pieces are nailed on with brass panel pins, but the small top piece is glued onto the corner piece with araldite. I tried exterior wood glue, but the oil treatment soaked into the wood and failed the joint. Araldite as usual is great.

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Wow, that looks absolutely amazing! I love the sarracenia’s, they make mine look a bit weedy :joy:


Thanks shmang. My ones in this cold frame are all the selected very rare and sought after ones like the leucophylla albas, particularly the front right area. They’re nearly all small/young at the moment, because getting offsets is not easy to find. I have others outside and loads of venus flytraps too.

Yours look fine. They need the opportunity to receive a minimum of 8 hours direct sun a day. No less, no shading. And if you want them big, you really need high humidity and warmth to get a long season, hence mine are in the cold frame

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Hi Count.d, thanks for the info, I am a total amateur at this, any info is much appreciated.

Wow indeed. Bloody marvellous. Decision now is where to put it.North South East or West Facing in the garden. Temperature is very hot south facing in the afternoon

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Thanks bluejays. I had limited choice where to put it and it receives 8 hrs of direct sun exactly. Part of the reason to raise it was to avoid being shadowed by buildings and things.

Splendid! :smiley:
Impressive work :+1:


how many watts per channel ?

That looks fantastic…can’t wait to see your next Fraim project!

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I have designed a carbon fibre wall shelf for a LP12 using available parts, but haven’t built it yet due to other things going on.

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When you finish the project I’d love to see it I am looking at moving my Uniti Nova upstairs and mounting it on a glass shelf or something similar at the end of our couch and adding stand mount bookshelf speakers to the room.

It’s a tight spot but I hope it will work

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