Choosing a foundation for your shipping container home can be challenging. There are some guidelines to consider to make it easier. Of course location is the number one concern when choosing the foundation. Lets go through a few scenarios, but before we go any further always consult a local engineer for the specifics in your area.
Shipping Container Homes Foundations on grade
This is just like what it sounds like “on grade”. On grade means on the ground. What you would normally do is have the bottom of the storage container a minimum of 8″ above the highest elevation of the ground.
In Florida where I live we use 2,000 s/f compaction as a base line, again you may have to consult with an engineer. Also we are figuring a 8″ x 40″ (320 s/f) container. We also are using a dead load of 35 lb s/f and a line load of 40 lb s/f for a total of 75 lbs s/f. If we multiply that times the floor area (75 x 320 = 24,000 lbs. This is important because we have to size the foundation accordingly.
Shipping Container Homes Foundations “Pads”
There are basically two types of pads. Poured in place and Precast. Either one will have to be in the ground. The depth in the ground depends of your geographical location. Frost lines is the big determining factor. Believe it or not Florida has a 12″ frost line. That means any foundation that is going into the ground has to be a minimum of 12″ into the ground. The further north, the deeper you have to go. Check your area.
As for size of the pads this is where the loads come into play. We are going to use the total load of 24,000 lb s/f. The pads sizes are going to be based on the total amount you want to use. Example: We want to use 8 pads, we would divide the 24,000 by the amount 8 which comes to 3,000lb load on each pad. Now remember the soil compaction of 2,000 lb s/f? So we will divide 3,000 lb s/f (load each pad) by 2,000 lb s/f (compaction of one s/f of soil) or each pad needs to be a minimum of 16″ x 16″ . The height is not that important but has to be able to support 3,000 lbs. There is another consideration and that is “topple factor”. This is the amount of force it will take to “topple” the shipping container home over.
Shipping Container Homes Foundations “piers”
Piers are like pads but generally are “above” grade. These should be sized in the same way as the “pads”. I would recommend no smaller that 16″ x 16″ and no less than 8 piers. Just like with the pads it is very important to “tie” the shipping container home down according to your location.
Shipping Container Homes Foundations “Spread footer”
A spread footer is the term used for the common 16″ x 10″ footer used on stem wall construction. The footer is continuous and reinforced with (2) #5 rebar. Generally the minimum concrete compression is 2,500 psi s/i.
This kind of foundation is good if you are wanting your shipping container home more permanent. This is also a good method to raise the home and have storage below.
These are three of the more common foundations for shipping container homes. Of course there are others. I will make mention that you can use timbers and they work quit well.