One structure on our property is built slab on grade. Located in the US in climate zone 6. This is a heated space which we will be removing part of. The removal will expose a lot of the slab to the elements.
Now, I assume that the slab is correctly constructed and has appropriate footings and is probably insulated underneath. (Assumed because we've had zero problems with it in 20+ years). However, we intend to cut away portions of the to-be exterior slab. The concern is that this will expose the slab to frost heave.
I am looking for suggestions as to how to protect it from this. Options I can think of include: - Adjust drainage to make sure water flows away. - Dig a new trench "footing" under the new slab perimeter, which presumably has to be down below front depth. (Not a load bearing footing, however - just a water diversion) - Dig a trench and use plastic or some other impermeable material to create a sloping surface to channel groundwater away from the slab. This would also have to go below frost depth.
These may not necessarily be mutually exclusive options. Cost is a factor, of course, but mainly I want to make sure I know how to do it correctly.
Edit - I think the foundation is a typical footing-below-frost-depth type. Not a shallow frost-protected design. This assumption is based on the age of the structure - built around 1990. According to this HUD report, at that time the shallow type was extremely uncommon in the US.