Enhancing the greenhouse effect

Written by

Edible gardens, Practical advice and DIY

We recently built a mini greenhouse to fit on our balcony so that we could get a head start on our summer seedlings.

Every construction or woodwork project can be thought of as an architectural project, no matter how big or small. I like to use SketchUp to plan my project. SketchUp is a 3D modeling computer program for drawing applications including architectural, interior design, landscape architecture, civil and mechanical engineering, film and video game design. I can draw the project to scale and estimate the materials required.

Below you can see how I have used SketchUp to develop a design for a mini greenhouse to fit on our north-facing balcony.

Line drawing of a two-tier plant stand, with rectangular trays on the upper shelf and four round plant pots on the lower shelf, supported by angled legs.

Concept for our new mini-greenhouse modelled in SketchUp

After purchasing the materials, I used this sketch to start building the mini greenhouse.

Two hand-drawn technical sketches of a shelving unit with measurements are placed on a wooden table. Nearby are a pair of pliers, a yellow toolbox, and some scattered water stains on the paper.

I used 35×70 sections of untreated, non-structural pine certified by the Forest Stewardship Council (FSC) for the frame. After cutting the pieces to size, I stained the timber to fit the aged style of the existing house, and then sealed it with a coat of varnish.

Several long wooden planks are laid side by side across two wooden saw horses, set on a gravel drive outdoors with trees and brush in the background.

A wooden workbench outdoors holds stacked planks, a tape measure, a set square, and a green power saw, with gravel ground visible in the background.

Several pieces of cut wooden timber and rectangular wooden frames are stacked on two saw horses outdoors on a gravel surface, with a traffic cone and other materials visible in the background.

Several rectangular wooden frames and slats, stained and drying, are propped up on two saw horses outdoors on a gravel surface.

I then started to assemble the frame using batten screws to have a solid frame, and added the polycarbonate sheet to the front.

A wooden saw horse standing on a gravel surface outdoors, with a car and another small wooden structure visible in the background. The saw horse appears newly built and sturdy.

A wooden stand holds three different-sized sieving trays. The structure is set outdoors on a blue tarpaulin, with building materials and trees visible in the background.

I did not plan the door until the end of the project. I decided to use a good old palette we had in the yard.

A wooden pallet lies on gravel with two planks, a green power tool, and a yellow spirit level placed on top. An orange safety cone and other pieces of timber are visible in the background.

A homemade cold frame made of wooden planks and clear plastic panels stands outdoors on two wooden beams, likely for gardening or plant protection. Forest and logs are visible in the background.

I then covered the rest of the frame and the doors with builder’s plastic and fastened it with staples to the frame. The tip here is to use low force on the staple and to put two staples on top of each other to form a cross to avoid the plastic ripping apart.

A homemade wooden mini greenhouse with clear plastic panels stands on a porch. Potted plants and trees are nearby, and forested hills can be seen in the background. Sunlight filters through the scene.

A small wooden glasshouse with transparent plastic panels stands on a porch. The door is open, revealing potted plants and seedlings inside. Sunlight shines on the structure and surrounding greenery.

A wooden cold frame with transparent plastic panels sits open on a veranda, holding trays of young plants and a pot, with greenery visible in the background.

A small homemade greenhouse box made of wood and clear plastic sits on a wooden balcony behind a balustrade, with potted plants nearby.

A small glasshouse with translucent corrugated plastic walls and a slanted roof, allowing sunlight to reach green plants growing inside. The structure is placed outdoors near a building.

In case it gets too hot inside the mini greenhouse (and it will!), I made it possible to slide both panels on top of the greenhouse to allow hot air to escape. Note though that the middle part is fixed. I used the same railing system sold with the polycarbonate panels and fixed them with small screws. You can see below that the thermometer inside indicates that the internal temperature of the greenhouse was 23 degrees (Celsius) on the day this photo was taken, whilst outside the temperature was only 8 degrees. Even on a cold day, the power of the sun can be harnessed.

A homemade green house with a transparent, corrugated plastic top sits on a wooden decking, surrounded by plants and greenery in the background.

A wooden planter box with a transparent plastic cover, partially open to reveal green plants inside, is placed on a veranda overlooking a grassy area and trees.

Close-up of the corner of a clear corrugated polycarbonate sheet, with sunlight highlighting its texture and internal channels. The background is blurred green foliage and wooden surfaces.

A close-up of a glass thermometer showing a temperature reading of about 22°C, with sunlight and a blurred outdoor background visible through a window.

That’s it, here the final result. We have put in our first batch of seedlings and cannot wait until we can transfer our tomato and other summer vegie seedlings from our heat pad set up indoors to this mini greenhouse. But more on that later. In the meantime, we cannot wait for the end of winter so we can get these seedlings into the ground.

Young green seedlings growing in trays inside a small wooden greenhouse with sunlight shining through clear plastic panels. The seedlings appear healthy and vibrant.

Young green lettuce plants growing in soil inside a greenhouse, with sunlight streaming through clear, ribbed plastic panels in the background. The leaves are fresh and vibrant, catching the sunlight.

I hope this may inspire you to create your own mini greenhouse. If you have any questions or photos of your own greenhouse projects, feel free to share them with us on Facebook.

#greenhouse #plants #garden #gardening #gardeners #gardenlife #gardeninglife #growyourown #growyourownfood #homegrown #vegetablegarden #woodwork #woodworking #tasmania #northerntasmania