Building a Greenhouse
For Wintering Herbs

Are you contemplating building a greenhouse in a small space? One that can be fixed to the ground? Maybe you abandoned that idea as an impossibility and resigned to having a walk-in portable instead.

Was it the limited space that put you off? Or was it the thought of actually building one?

Well, a walk-in portable might not be a sound choice and a waste of time and money into the bargain. The problem with them is that they`re super light and a bit flimsy.

Don`t get me wrong! They have their uses on balconies and patios. I know, because I have one. But if they`re not sheltered behind a strong building or wall they won't withstand the force of a strong wind. Next thing you know, your precious herbs will be no more!

Don`t despair! There`s a wide range of solid structures that will cater for your needs.

I opted in for a small 4 x 4 ft aluminium and polycarbonate greenhouse which doesn't give the impression of having much room at all. But that's the only size that could fit into the tiny wee vacant space that I had.

Well it all turned out well. Just what I needed and it can for you too!

Building a Greenhouse Foundation

First you need to have a solid base. But how do you go about fixing a greenhouse base to the ground?

The first step is to choose an area that has some sheltering if possible. There is a reasonably high garden fence to the side of mine, and a tall fence and building to the back.

The only drawbacks that could have presented a problem was that defensive yukka tree getting in my way, and having enough space to walk around the greenhouse for cleaning purposes.

So try and allow for at least a 2 ft clearance all around your greenhouse. Not unless you are rather large. If so, go for more.

My plot was full of hardcore, uneven and small. Building a greenhouse there didn't seem possible at first, but never-the-less it happened.

How? By careful planning and lots of self-confidence.

Check if the site is level. If not, you`ll have a bit of hard graft in front of you. Use a long straight piece of timber and a spirit level to make sure. Once you have achieved level ground you're ready to lay a foundation for the base.

The model in the photos came with a base frame and four legs which can be concreted into the ground. But I wanted to use gravel and a grid to keep the gravel from moving around a lot. It would also help with drainage because the soil in my garden has a lot of clay.

Steel base with legs for anchoring
Gravel grid

The materials and tools you will need for building a greenhouse and its foundations like mine are

  • a spade
  • a rake
  • a spirit level
  • builders sand
  • weed suppressant membrane
  • gravel grids
  • angled gravel
  • concrete mix
  • clear silicone sealant
  • a spanner
  • a screwdriver.
  • some kind of marker

If you want to try this neat idea of mine you will need to build your base frame first and use it to stake out the spots where you will dig holes for the legs and concrete.

Cut out a cardboard disc and slash it crosswise so it can be opened at a later stage

The next step is to dig the holes measuring about 12 cm radius.. Depending on what model you choose you can calculate the depth by measuring the length of leg that will be buried and adding a few more centimetres so they don't touch the bottom.

The depth of holes to accommodate my greenhouse legs was 20cm. Cover the dug out holes using a cardboard disc with a slit cross to push open later for the concrete.

Sand , Weed Suppressant Membrane
and a Gravel Grid

Shovel a layer of builders sand over the whole area. Avoid covering the cardboard discs. The sand helps fill any little dips in the soil.

Lay the weed suppressant membrane down. Locate where the centre of the cardboard circles are and mark the membrane with a marker or chalk cross.

Grid Filled with Gravel

It`s time to lay down the grids.

Connect the square grids together and carry it to the site. Highlight the squares on the grid with a bright chalk above the 4 crosses on the membrane. Now fill the whole grid with gravel but not those 4 marked squares.

Avoid filling them by plugging with newspaper or rags. Shovel gravel around the border of the grid.

Unplug the squares and cross cut the membrane with a sharp blade.

Push the cardboard discs open to expose the 4 holes. Now pour the concrete mix into them with care filling almost to the top.

Insert the legs and fill with water
Top with gravel when hard

Insert the four legs of the base making sure it is level. The base should lay flat on the gravel grid. Use the spirit level to make sure it's level.

The next step. Follow the instructions on the concrete mix packet for adding water. Wait the specified time for it to set.

It will take from 5 to 10 minutes with a quick setting concrete mix. Once the concrete has hardened you can cover the holes with gravel and you`re all set to start building a greenhouse - Construction part 2.

  1. HerbHints
  2. Outdoor Garden
  3. Build A Greenhouse

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