what is the reason for digging below the frost line

[brickierob1]

Hi everyone,

so my question is the above mentioned. although i have half a clue what the reasons are, i dont understand it fully.

the reasons why im asking is if i for example wanted to build a 3m half brick wall, say 5 courses high, it would seem excessive to me to dig a footing 3 feet deep.

so as i understand it the frost line in the southeast of england here is 450mm and i should dig 12 inches below this which would be shy of 3 feet. im i understand this correctly?

many thanks 

[A_L]

Soil expands when the water in it freezes, potentially causing uplift, but even NHBC do not require that much, and that's for load bearing, not decorative features.

 

https://nhbc-standards.co.uk/4-foundations/4-3-strip-and-trench-fill-foundations/4-3-3-ground-conditions/

[Onoff]

It's called frost "heave". You can protect against it I believe by wrapping in EPS.