How to Prepare Your Site Foundation

There are many factors to consider when prepping your site foundation for a portable accessory building. For this reason, there is no 'one-size-fits-all' solution for shed foundations, but there are some guidelines based on the size of shed and intended use of the shed. For the purposes of this guide, there are two categories of storage sheds: small sheds for general storage and large sheds/buildings for use beyond small storage.

In all situations, we highly recommend consulting a professional building inspector to provide personalized recommendations on preparing your own site foundation for your portable accessory building.

Please note this is general advice only, It does not take into account your objectives, financial situation or needs. Before acting on any information, you should consider the appropriateness of the information provided and the nature of the relevant financial product, having regard to your objectives, financial situation and needs.

Small sheds for tool and garden equipment storage

If you have a small shed, under 256 square feet, and plan to use it only as a tool shed for basic lawn and garden equipment, then you have three main options for your site foundation.

1. Place shed directly on ground for solid, well-drained soils

If your site has solid ground with good drainage that is not subject to flooding or holding water, then you can safely place our shed directly on the soil. Stateline Builders' sheds use a system of skids & joists that are chemically treated for ground contact. In our system, the skids are the only part of the shed in direct contact with the soil. The skid plus the joist creates a minimum of 7 ½ inches of airflow underneath your shed, keeping things dry.

  • Best for well drained areas not prone to flooding
  • No extra costs
  • Easiest foundation setup
  • Not suitable for flood prone areas

2. Stack shed on top of cinder blocks for flood prone areas

If your site does not drain easily and is subject to holding water, then you may want to place the building up on cinder blocks. Stateline Builders recommends using 4-inch solid cap blocks. Solid cap blocks are very affordable and can be found at your local hardware store.

  • Best for flood prone areas
  • Low-cost solution
  • Simple setup

How many blocks do I need?

For most customers, a single block height is enough. If you decide to stack up 2 blocks high, we recommend using a 3 block pier system that creates a larger footprint and fewer settlement issues. In a 3 block pier system, we will place 2 blocks side by side on the ground, with the 3rd block placed crossways. 

To estimate how many blocks are needed for your shed, consider the size of your shed. Blocks are often spaced approximately 6 feet on center down the length of each skid. If you are unsure about how many blocks to purchase, simply call Stateline Builders to speak with a knowledgeable team member.

What if my shed has a ramp?

For sheds placed upon blocks with a door ramp, it is important to note the height of the blocks increases the steepness and incline of the ramp.

Does Stateline Builders provide the blocks or set them up?

Stateline Builders does not provide the blocks as there is no extra room on the delivery trucks. Please have all the blocks on site prior to delivery. You do not have to position the blocks, simply store the blocks near the proposed location without blocking access to the site.

3. Lay a gravel pad for optimal foundation conditions

A pad of gravel is an optimal foundation for a small portable accessory building. Gravel provides excellent drainage, acts as a moisture barrier, evenly distributes the shed weight, and minimizes settling issues. See our guide on how to lay a pad of gravel for D.I.Y. instructions on this foundation type. Depending on your intended use for your shed and if your local building code allows for it, a gravel pad foundation can also be used on larger buildings.

  • Best foundation for small to medium sheds
  • Great drainage and even weight distribution
  • Medium cost solution (cost for gravel and lumber materials)
  • D.I.Y. options

Large sheds that will store large, heavy items or portable building with finished interior

For small to medium size sheds (under 256 square feet), a concrete slab is not necessary. However, in some situations, pouring a concrete slab is an easier and more affordable solution to achieve a superior, sturdy foundation. For large sheds or portable buildings with finished interiors, a permanent concrete foundation is recommended and, in some cases, may be required by law. Please consult a professional building inspector for a personalized recommendation for your situation.

Please refer to our detailed guide on preparing a permanent site foundation for horse barns and large accessory buildings.

  • Superior foundation for all building sizes
  • May be required for large buildings
  • Professional installation recommended

More foundation questions?

If you're still unsure which foundation option is best, our knowledgeable staff at Sateline Builders is available to make recommendations considering your intended use and location. However, it is best to consult your local building inspector. Foundations preferences and requirements vary between inspectors and regions, as there are many variables to consider.

More to learn this way...

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