The types of foundations for your shed

In order to make the right choice, you must be well aware of all the various aspects of each type of foundation so that it is well adapted to your construction project. Also knowing what type of work it represents is another point not to be neglected.
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Concrete block
Concrete pillars
Concrete slabs

Concrete block

This type of foundation is recommended for a shed. However, concrete pillars or concrete slab could also be used for a shed.

Remove the lawn from within the perimeter you have marked off and prepare the surface. If need be, you should provide for drainage, install a geotextile sheet and lay down gravel and sand.

Next, lay down Deck Block® concrete around the perimeter of the construction. You will require a minimum of eight, plus one for the centre. To ensure that the blocks are levelled in relation to the ground, use a regular spirit level. To ensure they are levelled in relation to one another, use a string level.

As well as being cost affective, this type of foundation is quite easy to build.

Concrete pillars

Contrary to a shed built on concrete blocks, one built on concrete pillars is not laid on the ground but elevated on a minimum of eight concrete piers buried about 4.5 ft (1.35 m) in the ground, below the frostline. To build such a shed, you will need a power ram or a manual hole digger you can rent if need be.

Each pier will rest on a 24 in. (509 mm) footing. A twisted steel rod, inserted into each footing, should extend through a tubular cardboard form and protrude at the top end of the form to anchor a 2 × 6 in. (50 mm × 152 mm) joist, laid flat, on which the floor will rest. The protruding end of the rod must be threaded to accommodate a nut, which will hold the joist in place.

To build the concrete pillars, pour concrete into the tubular form and the footing then compact it around the steel rod.

Remember that the chemical reaction, which causes concrete to set occurs over about 21 days. You should wait at least a week before erecting the shed. This will allow you to prepare the surface, which will be difficult to reach after the shed is fully built. If need be, you should provide for drainage, install a geotextile sheet and lay down gravel and sand.

Concrete slabs

To build a concrete slab for a shed, dig a hole about 15 in. (381 mm) deep, build a strong, steady form using plywood and 2 × 3 in. (50 mm × 76 mm) wood beams nailed diagonally to the outside of the form and resting on the ground. Lay a bed of well-compacted sand at the bottom of the form (we recommend you use a compactor), which you will then cover with a sheet of polyethylene before pouring steel- and mesh-reinforced concrete. These steps are essential if you want to protect the slab against cracking caused by ground subsidence, and against premature degradation due to humidity.

The hole should be deep enough to pour at least 10 in. (254 mm) of concrete over an area of about two to three feet around the inside perimeter of the form, reducing gradually to 4 to 5 inches (100 mm to 152 mm) at the centre of the slab.

You should also plan to attach the base of the walls to the 2 × 4 in. (50 mm × 100 mm) foundation sill. You can attach the foundation sill to the slab by nailing it to the form before pouring the concrete. Once you have nailed the sill to the frame, hang threaded twisted metal rods to the sill, every two feet. Once the concrete has been poured and has set, the rods will be permanently imbedded in it. The sill should normally be at the same level as the slab.

You can also drop the steel rods into the form, letting about 4 in. (100 mm) of threading protrude at the top. Once the concrete has set, you can drill holes into the bottom 2 × 4 in. (50 mm × 100 mm) beam of the wall - making sure they line up with the rods - and bolt the wall to the slab.

If you are planning a water inlet or drainage through a washbasin or through the floor, you will need to install the required plumbing and other facilities before compacting the ground and pouring the concrete.
You now have a better knowledge about foundations and you can choose the one that is the most suitable for your needs and convenient for your construction project. For more information, if necessary, you may visit and ask specialists for further help.
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