Fill Dirt For Raised Concrete Slab Foundations

We will have to build our lot up, probably about 4-6 feet to get out of the NEW FEMA flood zone.

The lot will not be surveyed for a couple weeks, however, I have seen some people digging pond and have signs "dirt for sale".

I am hoping to get a bargain and was wondering IF I do, where is a good place
to put the dirt?

I was thinking on the side of the lot so they can properly pack it but I am basing that on absolutely nothing! :)

Thank you, Michelle

Hi Michelle,

Good foresight on your part!

Whenever I need fill dirt, I have to “pay through the nose” to get it hauled in. When I don’t need dirt, it’s everywhere and it’s cheap. This is one of “Murphy’s (Home Building) Laws”.

Anyway, if you do get a good price on the dirt, you should be able to stockpile it on your lot. Be sure it is out of the way of the actual “footprint” of your future house so that you don’t have to move it again until you are ready for it.

To tell if you are getting a good price on the dirt, call a couple of excavators and get some prices for fill dirt. They charge by the cubic yard, or by the ton.

It’s not a bad idea to cover the dirt if you can, as it is easier to work with dry dirt when you are ready to use it.

BUT, using fill dirt for a raised slab foundation is not really the best way to go.

Fill dirt is difficult to compact and can lead to other problems down the road such as settlement and cracking.

Here’s a good tip (from The Engineered Wood Association) you may want to consider in lieu of 4 to 6 feet of fill dirt.

Reasons to Build Raised Wood Floors from the Engineered Wood Association.

Reason #5.The construction advantages of a raised wood floor system solves the problems associated with floodplains and sloping lots.
Raising a slab with fill dirt to meet floodplain elevation requirements can be expensive, time consuming and difficult to properly compact.

A raised wood floor system provides a practical and affordable solution for meeting code and keeping a home above flood waters.

For sloped lots, a raised wood floor on piers (See my "Crawl Space" page, Carl) is more economical and practical than building a “cut and fill” slab foundation. Less soil is disturbed, reducing erosion, and the piers eliminate the need for reinforced retaining walls.

Michelle, if you decide to still build with the raised slab, I strongly recommend you backfill the foundation (under the slab) with clean sand, not dirt.

Sand compacts better (it compacts pretty well just by its’ own weight) and provides excellent drainage. It’s more expensive than dirt but worth it.

Remember, the foundation is (to me anyway) the most important step in building a house.

But hey, you will probably still need the dirt for grading around the foundation.

Carl Heldmann,