Frost Line Depth By ZIP Code

How do you find the frost line depth for your ZIP code?

Enter your ZIP code and the lookup matches it to the city or county that issues building permits there. It then shows the frost line depth written in that place’s adopted building code, or the state rule where the state sets one. Your building department has the final word.

1. 1

   Enter your ZIP code

   Matched to Census ZIP areas and the counties they touch.

2. 2

   We find the authority

   The city, county or state that issues your building permit.

3. 3

   We read its code

   The frost line depth written in its adopted code, with a link.

4. 4

   You see how sure it is

   Verified, state-set, or no official local value.

Frost line depth by state

Each state handles frost line depth differently: a few set one number, some set it by county, and most leave it to each city or county code. Tap a state, or open the frost line map.

What do you do with your frost line number?

Your frost line number sets the minimum depth for anything that must not move when the ground freezes and swells.

• 

  Deck Footings

  Footings for a deck attached to the house go below the frost line, and at least 12 in down.

• 

  Fence Posts

  Bury about half the fence height, and go to the frost line when posts are set in concrete.

• 

  Water Lines

  Bury the service line 6 in below the frost line, and at least 12 in deep.

• 

  Sheds

  Detached sheds up to 600 sq ft can skip frost footings (IRC R403.1.4.1).

Building something else? The footing depth guide covers porches, garages, gazebos, pole barns, slabs and more, and the water line guide covers sewer, septic, irrigation and utility lines. For the code itself, read the IRC frost depth rules.

Is the frost depth map from the weather service the same as your frost line?

No. The National Weather Service frost depth map shows how deep the ground is frozen this week at its stations. Your frost line is the minimum footing depth set by the building code, and it stays the same every year.

More: what the frost line is · current frost depth

How do we check each frost line depth?

Every value in the lookup comes from a published document: a city or county code, a state code table, or a state rule. We read the document, record where the value came from, and label each place with one of three tiers.

Verified official values

721

Local codes read

280

Places covered

1,678

Last checked

Oct 2026

• Verified The place’s own code or the state rule sets this number.
• No official local value We show nearby official values and who to ask.

How we verify · Sources