Guide: How to Build a Greenhouse Base

If you’re reading this article, chances are you are a greenhouse owner and already know what types of greenhouse bases are available out there. 

What you’re looking for is a ‘how to’ guide on building a greenhouse base of your choice.

Whether you’ve decided to go with a concrete or wooden base, you’re in luck because below you’ll find a step-by-step guide on how to build a greenhouse base for your Planta greenhouse.

A few things to keep in mind before we dive deeper into the ‘how to’ guide. 

  1. The base is one of the key factors for your greenhouse project to thrive. If you don’t have a solid, perfectly leveled base, the doors of your greenhouse may not close properly, harsh weather could cause damage or the entire structure could shift over time adding strain on the panels. 

  2. Before choosing a specific base, consider the site composition (if the soil is compact or slope), if you live in a freezing area, and how permanent you want it to be. 
  1. The base should be exactly the shape and size of your greenhouse structure. It must be placed in an area protected from floods, preferably 6-inch raised from the ground so the polycarbonate hangs over the base making sure you won’t get water underneath nor in your greenhouse.

Alright, now that we have this covered let’s get to work!

Wooden Perimeter Base

This is one of the most common bases among our Planta greenhouses customers because it is easy to build and will last a lifetime if built with the correct materials.

1. Choose The Materials

You can choose between two options: pressure-treated wood or naturally resistant wood, like cedar, redwood, or black locust.

2. Build The Wooden Frame 

Once you’ve chosen the wood, make a 6-inch width perimeter base in the measurements of your greenhouse. Use 6x6 timbers preferably. You can start by laying out the frame on the floor before attaching the ends. Use a carpenter’s square to make sure you have the right 45 degrees angle in each corner and intersection, and level it both vertically and horizontally.

The wooden frame must be fixed to the ground. An easy way to do this is to drill holes in the wood, use two bars between 2-foot sections, and hammer them straight into the ground. This will support most commercial greenhouses.

3. Assemble The Greenhouse

After building your wooden frame to match your greenhouse measurements, it’s time to sit the metal base on. Screw the fastening bands to the wood base as low as you can go, remember you need to be able to adequately tighten the ridge straps, and allow for further tightening later as needed.

Wooden Base

A wooden base is a solid option to build your greenhouse on and it requires just a few more steps than the wooden perimeter base.

The steps below are the continuation of the process after building the wooden frame mentioned above. 

1. Level your base

Another way to fix the wooden frame to the floor is to drive level 6x6 inch posts into the ground which you can secure with concrete and attach the wood frame on top of them. The number of stakes or posts will depend on the size of your greenhouse. 

You want your base to be a very leveled surface so you can use string levels for the corners of the platform to make sure it is even. Another tip to ensure your frame is perfectly squared is to measure from corner to corner to see if the diagonals are the same size.

2. Bridge The Structure

Screw wooden planks across the frame. Depending on the size of your greenhouse it may be necessary to bridge the structure and place sized boards between each of the interior boards. The bridging will make a more solid foundation ensuring the proper spacing to avoid any shifting in the future.

3. Add a Wooden Cover

Place boards on top to cover your deck and secure them with nails or screws. You can always add steps at the entrance of your greenhouse to give it a nicer look!

Here’s a great YouTube video that shows how to do this:

Concrete Base

Building a concrete slab might cost more upfront, but it is also a nicer and more secure option for a greenhouse foundation.

While you might have an existing deck or concrete slab to sit the greenhouse on, below we will describe the steps to create a concrete base from scratch.

1. Build The Perimeter 

Mark 4 corners at the size of your greenhouse with stakes. Go around the 4 points using string levels and secure them at the desired height. As mentioned earlier, it is recommended to calculate a 6-inch height.

2. Level The Ground

Make sure the soil is leveled before building the wooden perimeter. Dig a little trench to hold boards on each side at the level of the strings you previously measured.

This formwork is used to hold the concrete that will be poured later. You can use recycled boards.

3. Pour The Concrete

Once the formwork is leveled and secured, place a layer of gravel, sand, and water to get a more stable base on which you’ll pour the concrete. Before making the concrete mix, place a grid of rebar with 15x15" squares

The mesh should be a few centimeters above the ground. You can place plastic tiles at various points under the grid. Pour the concrete, spread it, and screed at the level of the woods to smooth the surface. To avoid cracks it is necessary to keep watering the base as it dries.

This may require some technique, so if you’re not sure how to do this, hire a professional to do it for you.

4. Assemble The Greenhouse

Allow drying for two days before removing the wooden perimeter and assembling the greenhouse. The concrete takes 21 days to dry completely. Use anchors to drill into the concrete and secure your greenhouse.

Concrete Perimeter

Building a concrete perimeter could require tools you don’t have handy at home and a bit more expertise. The height of a raised perimeter may vary from 1 to 2 feet depending on your site and how tall you want it as the greenhouse will be set on top of it.

This wall-type foundation will make your greenhouse the centerpiece of your outdoor space. 

1. Mark The Footing

Mark the corners with stakes, and dig a trench where the greenhouse will be sitting. Make sure that the base is solid and even.

Go down with the trench about 8 inches and 1 foot wide for the footing.

2. Stack The Blocks

Pour concrete into the trench and start stacking the blocks on top and fill them up with concrete. You want the blocks to be well leveled so you can use a wooden frame and a level device to make this task easier.

3. Finish The Coating

After stacking all the blocks at the desired height you can put the finish coat on top. It also can be finished with stonework, brickwork, or any other material to suit your patio décor. 

Now you’re ready to build your greenhouse base. Don’t overthink it, a soil or earth base is also an option.

Ask for our expert's help in case of any doubts and don’t forget to take a look at the installation videos we have recorded for assembling Planta Greenhouses’ various models.

Back to Greenhouse Bases

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