What type of foundation should I use?
The foundation of any building is the first and one of the most important considerations of any building project. Sheds are typically smaller buildings but they still need a good foot print. When it comes to foundations for sheds, there are 4 common options, concrete slab, sonotube, stone pad, and blocks. In this article I will discuss each type of foundation and it’s strengths and weaknesses. In most cases, our top recommendation to people planning a shed is to use sonotubes, because of their cost to benefit. After reading, consider what the best match for your unique situation would be.
This kind of foundation is made by excavating a level space, compacting gravel at least a few inches and pouring concrete (at least four inches thick) into a form and finishing smooth or textured as it dries.
A concrete slab is a top of the line foundation that it is long lasting and solid.
A concrete slab will not rot or be damaged by running a lawn tractor or snow blower across it.
It is a good foundation if you plan to store heavy items in your shed.
This extensive foundation is rarely necessary for a shed but is worth considering if the shed were to house a vehicle or heavy equipment.
A concrete slab needs a level area to be installed. If your area is not level it will need some additional excavation done before the concrete is poured.
Unlike a shed with a wood floor, a shed with a concrete slab can not be moved to the other side of the yard if you decide you don’t like where it is.
A concrete slab is the most expensive option especially when additional excavation is needed to make a level site.
Sonotubes are rigid round forms that are placed in a hole, usually four feet deep and anywhere between 8 and 12 inches in diameter. Concrete is poured into the round form and they are used as a footing for posts and beams. This is an excellent choice for a shed, especially a larger shed or one on uneven ground.
A sonotube foundation is a very solid foundation that is frost protected, no need to worry about frost heaves which can soon make doors and windows not work right.
Sonotubes are a good choice for a foundation when the area is not level. Sonotubes can be used to make a level place for your shed without major excavation.
Sonotubes can be very difficult or impossible to install if the soil is rocky.
(NOTE - “Dig safe” should always be called to check the area prior to digging)
A stone pad is just what it sounds like. Sometimes the sod is excavated from the footprint and stone gravel fills the space. This is sometimes compacted, but is not always necessary. If there is a slight grade the pad can be made level by making a retainer with wood and stakes.
A stone pad is an excellent lower cost option for your shed foundation.
A stone pad that is built larger than the shed footprint is an excellent way to provide water drainage around the shed and reduced dirt splash back onto the shed siding.
To build a stone pad, small equipment such as a mini excavator and a 1 ton dump truck will need access to the site.
A Block Foundation is made by laying out pavers or concrete blocks in a grid that the posts and beams rest on. Sometimes the blocks can be dug in or gravel can be added below them to adjust the height so that all the blocks are level relative to each other.
Blocks are very inexpensive to use.
Blocks are great for smaller sheds that you may want to move in the future.
Blocks are a good choice to bring a site up to level. (NOTE - it is best not to use block if the site is more than 8”-12” out of level)
A block foundation is not frost protected, so certain times of the year the doors may bind because of frost heaves.
A block foundation is not good in areas where the soil tends to be wet or soft, the blocks may sink causing the doors to bind.
A block foundation most likely will need to be adjusted periodically, especially if used on larger sheds.
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Located in Medford, MA 02155 - Phone (857) 888-1146
Located in Medford, MA 02155