Foundation for a greenhouse: types of structures and step-by-step instructions for laying

Any greenhouse’s stability and longevity depend on building a strong foundation. Whether you’re a novice or an experienced gardener, knowing the various kinds of foundation structures and how to install them correctly will guarantee that your greenhouse remains sturdy throughout the year. This guide will take you through the different options and provide you detailed instructions on how to lay a foundation.

There are various foundation types available, each with unique advantages. The choice depends on your needs and budget, ranging from straightforward, quick-to-assemble options like wooden or concrete blocks to more durable options like poured concrete slabs. Selecting the correct type for your greenhouse is crucial because each has different installation requirements and methods.

It is imperative that you properly prepare the site before you start. This entails choosing a level spot, tidying it up, and making sure there is adequate drainage to stop water buildup. A well-prepared site will facilitate the laying of the foundation and help avert future problems.

The three most popular types of greenhouse foundations that we will discuss in this article are poured concrete slabs, concrete blocks, and wooden foundations. For every type, we’ll give you thorough, step-by-step instructions so you can construct a stable base for your greenhouse with assurance. These tips will assist you in building a foundation that will support your greenhouse for many years to come, regardless of whether you choose a more substantial concrete structure or a straightforward wooden frame.

Type of Structure Step-by-Step Instructions
Concrete Slab 1. Mark the area. 2. Dig out the foundation. 3. Build a frame. 4. Pour concrete. 5. Level and smooth the surface. 6. Allow to cure.
Wooden Frame 1. Clear and level the ground. 2. Lay a gravel base. 3. Build a wooden frame. 4. Secure with stakes. 5. Fill with soil or gravel.
Concrete Blocks 1. Mark the perimeter. 2. Excavate the trench. 3. Lay gravel. 4. Place concrete blocks. 5. Fill gaps with mortar. 6. Ensure level alignment.

Functions and features of the foundation for a greenhouse:

When constructed on a sturdy base, a garden greenhouse will function with greater dependability. Moreover, it offers several other benefits:

  1. The greenhouse will stand firmly on the ground, which means it will not be carried away by strong winds.
  2. Garden pests will not reach the plantings.
  3. The building on the foundation will rise above the ground, and this will reduce the percentage of heat loss.
  4. Plants will be completely safe from precipitation and frost.

But you should also consider the greenhouse’s actual dimensions when selecting the kind of base. If the frame of a small greenhouse box is sturdy, a foundation might not be required, but a base is required for larger structures.

Types of foundations

Differentiating between the following building options is based on the material of greenhouse walls:

  • made of wood;
  • made of concrete;
  • from blocks and bricks;
  • from pillars and piles;
  • from a monolithic slab.

Every variety has subtle differences.

A wooden base is portable (it can be moved from one location to another once it is disassembled), affordable, and simple to install and use. One of the drawbacks is the lack of strength.

Strip concrete foundations are the most basic type, and they have the benefits of strength, durability, and moisture resistance. The drawbacks include the labor-intensive nature of the work, inadequate thermal insulation capacity, and comparatively high labor and material costs.

Because they are easier to install, more durable, and do not deform in response to temperature changes than strip type materials, blocks and bricks are a good choice for heated greenhouses. Low moisture resistance and the requirement for extra thermal insulation are among the drawbacks.

Strength, simplicity of assembly, and the ability to be installed in places with challenging terrain. The drawbacks include the requirement for extra insulation and a stiff base strapping. Corrosion can affect pile foundations.

Slab foundations are the most dependable and long-lasting because they are steadily fixed, stable, and can be built on any kind of soil. Slab foundations also effectively keep pests away from seedling roots. The high labor and material costs, the requirement for extra thermal insulation, the requirement for a drainage system, and the need to maintain a steady microclimate are among the drawbacks.

Step-by-step instructions for laying

The size of the foundation, the location of the building, the removal of vegetation and debris from the construction site, and the marking of the area are all examples of preparatory work. The steps involved in the process are as follows:

  1. The territory of the greenhouse is determined.
  2. Vegetation is removed from it.
  3. The boundaries of the building are marked with pegs and rope.
  4. A trench is dug according to the markings: the top layer of soil is removed, then the digging depth is determined for each type of foundation.
  5. A layer of waterproofing (for example, thick film or roofing felt) is laid on the bottom of the trench.
  6. Depending on the type of foundation, a sand and gravel cushion is laid on top of the waterproofing.

Under the foundation, every corner must be at a straight angle. The traditional method of checking accuracy involved stretching the ropes diagonally to the opposite corners and identifying the intersection. Every angle is 90° if the ropes cross in the middle.

Tools and materials

The necessary toolkit ought to consist of:

  • strong rope or cord;
  • pegs for marking;
  • tape measure, building level;
  • hammer and nails, anchors and corners for fixing the structure;
  • self-tapping screws, screws, screwdriver or drill (if necessary);
  • hacksaw, shovels for excavation.

Depending on the type of foundation, different materials will be needed, such as beams, blocks, bricks, and mortar made of cement and sand.

Laying a foundation from a bar

The most straightforward material for building a wooden foundation is profiled timber, which has a cross-sectional area of 100 by 100 mm.

The methodical procedure for building a wooden greenhouse base is as follows:

  1. The timber is laid on the laid roofing felt and connected “in a paw” or “in half a tree”, then fastened with corners.
  2. The resulting base is placed on the bottom of the trench, the evenness is checked with a level. If necessary, it can be leveled horizontally by adding gravel or sand.

In this instance, the trench is 150 mm deep and 80 mm wider than the timber’s thickness.

Laying the foundation from bricks

Red brick is suggested for masonry because of its strength. Here is the technology:

  1. Medium-fraction crushed stone is poured onto the bottom of the prepared trench in a 5 cm layer.
  2. A concrete mixture of “cement-sand-gravel” (1:3:5) is prepared, mixed with water and poured into the trench.
  3. After 2 weeks, roofing felt is laid on the concrete for waterproofing.
  4. Bricks are placed on top of the roofing felt, between which anchors should be installed to secure the frame.

Depending on the size of the greenhouse, one or more masonry rows may be sufficient. Cement mortar is used to secure the masonry.

Laying a strip foundation

The trench’s depth and width for this foundation should be between 30 and 50 cm and up to 20 cm, respectively. It is necessary to set up removable formwork made of edged boards when laying a strip foundation. Following installation, the trench is filled with a solution made of cement, sand, and fine-grained crushed stone in a ratio of 1:3:3. A month is needed for the foundation to completely harden.

Laying a block foundation

The process of laying blocks is similar to building a brick foundation in that: first, a trench that is at least 25 cm wide and at a depth determined by the freezing point of the soil is dug. Next, a cement-sand mortar containing gravel filler is mixed and poured. Finally, the prepared blocks are pressed like bricks along the trench’s entire perimeter.

The leftover solution is used to fill the spaces between the blocks, which should be placed flush with the ground. Soil backfill is used to compact the masonry on the sides. Once the foundation is solid, you can start constructing the greenhouse.

Laying a columnar pile foundation

This kind is meant for portable greenhouses that aren’t used during the winter. You will need six to eight concrete pillars for installation.

  1. Piles are installed along the marked area – 4 at the corners, the rest – along the perimeter with a step of 0.9 m.
  2. A trench is dug between the pillars to a depth of 1 m, its width will be equal to the width of the concrete pillars.
  3. Roofing felt is laid on the bottom for waterproofing, then a reinforcement grid is laid there to strengthen the structure.
  4. A permanent formwork is arranged around each pile, where a solution is poured for fixation.
  5. Edged board is laid and secured on top.

To prevent the greenhouse from skewing, each pile needs to have its installation done evenly. This means that all of the posts need to be at the same height.

Laying a slab foundation

Although it takes more work to lay, this foundation is the strongest. Additional reinforcement in the form of a reinforcement grid and drainage will be needed for its construction.

The technology used in construction is as follows:

  1. A pit is dug for the foundation, the dimensions of which should be 10 cm larger than the greenhouse. The depth of the pit is taken from 30 cm.
  2. The bottom and walls are waterproofed with geotextiles.
  3. Formwork is installed along the walls of the pit, protruding above the ground level by at least 20 cm.
  4. Drainage is installed in the center: a corner pipe is fixed, pipe sections are connected and brought out above the ground surface.
  5. The bottom of the pit is filled with sand 10 cm high. A layer of fine gravel 5 cm high is placed on top. The backfill is tamped.
  6. Reinforcement is laid on a sand and gravel cushion, tied with wire, after which concrete mortar is poured.
  7. The surface is carefully leveled.

It is advised that the future greenhouse frame be fastened with pins driven into a slab of concrete.

Video: Polycarbonate greenhouse foundation

You can view a video on how to install a polycarbonate greenhouse’s base, for instance.

Selecting the appropriate base for your greenhouse is essential to guaranteeing its durability and steadiness. There are various structure types to take into account, each with a unique set of advantages. Choosing a foundation type that is appropriate for your needs and locality is crucial, regardless of whether you want a gravel foundation, a wooden frame, or a concrete slab.

Although installing a greenhouse foundation may seem difficult, it is actually quite simple if you break it down into smaller, more manageable steps. First, pick a spot that has adequate drainage and sunlight. Remove any plants and debris from the area. Next, determine the greenhouse’s perimeter and mark it. After that, you’ll need to level the ground or dig trenches depending on the type of foundation before laying the foundation material.

Make sure the concrete is smooth and level before mixing and pouring it for a foundation. Make sure the wood has been treated to withstand moisture if you’re using a wooden frame. To create a stable base for a gravel foundation, compact the gravel firmly. You can start assembling the greenhouse structure once the foundation is in place, knowing that it is supported by a sturdy base.

In addition to providing support, a solid foundation shields the greenhouse from the weather and any future ground movements. It is worthwhile to invest the time necessary to prepare and install the foundation correctly since the greenhouse will remain sturdy and operate well for many years. Recall that laying a solid foundation is the first step toward creating a successful and fruitful greenhouse, so treat it with the respect and care it requires.

For a greenhouse to be stable and long-lasting, it must have a strong foundation. This article examines several foundation options that are appropriate for greenhouses, ranging from straightforward wooden frames to more robust concrete bases, and offers simple, step-by-step installation instructions for each type. Whether you’re a novice gardener or a seasoned builder, you’ll find helpful advice and easy-to-follow instructions to help you build a strong and dependable greenhouse foundation that fits your unique requirements and surroundings.

Video on the topic

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Andrey Ivanov

Experienced civil engineer with more than 20 years of experience. Specializing in the construction of industrial and civil facilities. Author of many publications in professional journals.

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