Building Site Preparation Tips


Before starting on your excavation or digging for foundation, you must find out and mark the location of your septic pipes, electric lines, etc.   Call 811 before you dig!

Whether you are getting ready to build a barn, a house or small storage shed, the first step is to prepare your building site.  The properly prepared building site is very important and any "short-cuts" or "money-saving" advices should be avoided.  Choose your building site carefully.  Whenever possible try to avoid wet areas, low spots and big trees.  An ideal building site is a slightly elevated, level and sunny spot away from big trees, septic lines, wells, etc.


Site Preparation

To prepare your building site, you must do some excavation work to take all of the top soil off and to level your site.  Put all of the top soil aside incase you'll ever need to do landscaping around your building.  When doing excavation, make sure you reach hard ground.  In either case, you should excavate at least 6" deep to accommodate 6" of crushed stone.  When doing site leveling, try to use a transit and make your site as level as you possibly can.


In cases, where your site is slightly sloped or in a low spot, you might need to do some backfilling to level your site or to elevate it.  Backfilling can be done with a regular fill or compactable crushed stone such as 2-A Modified stone.  Never use top soil to backfill your site.  For best results, it's important not to backfill the whole site at once.  You should do backfilling in 6" thick layers, compacting each layer before adding the next one.

Sloped Site

If you don't have a level site, you will need to deal with a slope.  Some slopes are steeper than others and will require extra excavation to prepare your building site.  There are at least 3 different ways you can deal with a slope.  Images below show a level site and 3 ways to prepare your building site on a slope.

Option #1 - The cheapest way to prepare your building site on a slope is to further excavate into the bank (approximately 8'-12' away from your actual construction site) and cut the bank at 45°.

Option #2 - Another way is to cut into the bank and to install a landscaping retaining wall.

Option #3 - A third option is to cut into the bank and use your building's foundation wall as a ground retaining wall.  This option may be used to construct a Bank Barn (providing your slope is steep enough) or any other building that requires conventional foundation.

In either case, you will need to design and excavate your site in such a way, so most of the rain water is diverted away from your building.  In some cases you will also need to incorporate a water drain system by installing necessary drain pipes, French wells, etc.


Building Site Preparation Images

Stone Base (Subbase) Preparation

It's important to note that not every building site is the same and might require the use of different type of stone to be used for base preparation.  In most cases, you might get away with 2 types of stones.  In other cases, you will need at least 3 different kinds of stone.

Option #1 - On a dry and elevated site where water drains well and is not a problem a regular compactable stone such as 2-A Modified might be sufficient.  Spread 4" of stone, compact it well and your subbase is done.  If you are pouring a concrete slab, you will also need to add a layer of 3/4" clean stone on top of your subbase.

Option #2 - In situations where your building site is either located in a low spot or in a wet area, you might first need to use a layer of bigger stone such as 3" ballast stone, then a layer of smaller stone and finally a layer of 3/4" clean stone (if pouring concrete slab) or 2-A Modified (if leaving a dirt floor).

Note: It's always a good practice to compact your subgrade (soil) before spreading any stone and to spread the stone in max. of 6" layers, compacting each layer.  If you had any trenches dug for septic pipes, cables, etc., you must also fill the trench in 6" layers, compacting each layer with a vibrating compactor.  It is important to compact the soil when filling your trenches so it would not settle and create any problems.

Preparation of a Stone Base for Concrete Slab

When preparing your site for a concrete slab, you need to spread about 4" of 3/4" clean stone on top of your existing and properly prepared stone base (subbase).  Then again, level the stone and compact it.  Set up your concrete form and put a wire mesh in place slightly elevating it above your stone.  If your building is to be insulated, you must also place a vapor barrier on top of your base.  In our opinion, the combined thickness of both subbase & the base should be a minimum of 6" (when compacted).  Only in some cases, if you have a perfect site that drains well and slightly elevated, you might get away with a 4" of combined stone base.


Stone Base Preparation