The Importance of Rebar in Your Greenhouse Foundation
Every “How to Build a Greenhouse” book normally starts with the foundation as the first big step in the construction. If you decide to use concrete as a foundation for your greenhouse plans, you should consider using rebar to add stability and strength to the concrete. This rebar consists of specially treated steel that is laid in the poured concrete to add strength. Concrete is a great choice for a foundation material and will provide durable support for your building that can past decades. While hardened concrete provides outstanding strength for compression, it’s weaker under tension. As a foundation for your greenhouse, this means that it will not shrink under the weight of the structure but does not handle lateral movement of the ground very well. The constant expanding and shrinking of the ground that harsh winters can cause will twist a foundation and can lead to failure of the concrete over time. By adding rebar to the concrete when poured, you can increase its resistance to this type of failure.
Concrete is an incredible stable and durable material that is inexpensive compared to other options for a DIY greenhouse foundation. The composition of concrete provides great resistance against compression, but is weaker when pulled. The rebar is added to help minimize the stress a concrete foundation experiences along its length and helps to keep the floor and foundation of the building stable.
Rebar Has Been Used For Decades
Rebar isn’t a new discovery and actually dates back to well over 150 years ago when it was used to strengthen the frames of buildings. By adding rebar to the material used for construction, the builders were able to create structures that were taller and more durable. Many of these older structures actually featured the rebar as part of their façade as another one of the building’s architectural elements. With concrete, the rebar is hidden within the material but still helps to bolster its strength against tearing and cracking.
Rebar Has Other Benefits for Your Greenhouse Foundation
In addition to the rebar supporting the concrete is also helps to stabilize its temperature. Because different parts of the foundation may be exposed to slightly varying temperatures throughout the day, there is always a threat of uneven expansion of the concrete. The steel rebar is an excellent conductor of heat and can help to transfer any difference in temperature throughout the foundation. This prevents these localized hot and cold spots from damaging the foundation. The thermal conductivity of the rebar also helps to eliminate cracking of the surface of the foundation and will better stabilize the entire structure. In a typical DIY greenhouse foundation, the rebar is placed in the concrete as a loose frame that is formed by both vertical and horizontal sections of rebar. These are normally tied together to form the frame by thin wires that hold them in place. This frame is then completely covered by the concrete in the foundation to form a single structure. For smaller concrete foundations the rebar may be less extensive and simply placed in the foundation horizontally.
New Types of Rebar Are Available
Steel rebar is by far the most common material used in greenhouse foundation applications today because of its attractive combination of low price and durability. It is easy to work with and provides a great weight to tensile strength ratio. It also has a very similar temperature coefficient to the concrete, which allows it to expand and contract in a similar way when temperatures change. This is very important because of the tight bond that forms between the rebar and the concrete. If either one expanded more quickly than the other with temperature changes it would cause a fault in the foundation.
In recent years there have been a number of other materials used in place of steel rebar that include a fibre-reinforced polymer that is available in both rod and mesh configurations. This material is mostly used in very corrosive environments to prevent damage to the steel that might occur under these extreme conditions. With most DIY greenhouse foundations, standard steel rebar will work fine and can extend the life of the building by a decade or more when used properly.