Frostline.info

Frost line depth in Wake County, North Carolina

Frost reaches about 11 inches in typical soil across Wake County, from 10″ in the mildest ZIP code to 13″ in the coldest. Codes in this climate commonly set footing depth at 12 to 18 inches.

Shallow frost
Estimated frost depth
11″
typical silt/loam soil
Typical code footing depth
12–18″
rule of thumb for this climate
Design freezing index
124
°F-days, 100-year winter
ZIP codes covered
33
#41 of 100 counties in NC (1 = deepest)
11″ 0″12″24″36″ ground frozen
Est. frost (typical soil) Typical code footing depth Clay–sand range

Frost depth by soil type

Soil typeEst. frost depth
Sand / gravel (drains well)14″
Silt / loam (typical yard soil)11″
Clay (holds water)9″

County average. Methodology.

Verify before you dig. These are climate-based estimates. The legally required frost depth is the figure your building department publishes in its IRC Table R301.2 (climatic and geographic design criteria). Call the Wake County building or permitting office in North Carolina and call 811 before digging.

Frost depth by ZIP code in Wake County

ZIPCityEst. frostCode range
27502Apex11″12–18″
27511Cary11″12–18″
27513Cary11″12–18″
27518Cary11″12–18″
27519Cary12″12–18″
27523Apex11″12–18″
27526Fuquay Varina11″12–18″
27529Garner10″12–18″
27539Apex11″12–18″
27540Holly Springs11″12–18″
27545Knightdale10″12–18″
27560Morrisville12″12–18″
27562New Hill11″12–18″
27571Rolesville12″12–18″
27587Wake Forest13″12–18″
27591Wendell11″12–18″
27592Willow Spring10″12–18″
27597Zebulon12″12–18″
27601Raleigh10″12–18″
27603Raleigh10″12–18″
27604Raleigh11″12–18″
27605Raleigh10″12–18″
27606Raleigh10″12–18″
27607Raleigh10″12–18″
27608Raleigh10″12–18″
27609Raleigh11″12–18″
27610Raleigh10″12–18″
27612Raleigh11″12–18″
27613Raleigh12″12–18″
27614Raleigh11″12–18″
27615Raleigh11″12–18″
27616Raleigh11″12–18″
27617Raleigh12″12–18″

What this means for your project in Wake County

Deck footings & piers

Footings must bear below the frost line and at least 12″ below undisturbed ground. For planning in this area, budget for holes around 18″ deep until your permit office confirms the exact figure.

Fence posts

Set posts at least one-third of their above-ground height. Where frost heave is a problem, carry concrete footings below the frost line (about 12″ here in typical soil) and bell or taper the bottom.

Water & irrigation lines

Bury supply lines below the frost depth. Your water utility or plumbing code sets the minimum cover; freezing is rare, but exposed pipes still need insulation.

Slabs & frost-protected foundations

Frost-protected shallow foundations (IRC R403.3) use the 100-year air freezing index — 124 °F-days here — to size perimeter insulation, letting footings sit shallower than the frost line.

Weather stations used

NOAA weather stationDistance100-yr AFI
Raleigh-N C State Univ, NC1 mi102
Raleigh Durham, NC8 mi151
Durham, NC23 mi125
Moncure 3 Se, NC25 mi141

Nearby counties

Common questions

What is the frost line depth in Wake County?

About 11 inches in typical soil, based on NOAA's 100-year air freezing index. Across the county's ZIP codes the estimate runs from 10 to 13 inches.

How deep should footings be in Wake County, North Carolina?

Codes in climates like this commonly require 12 to 18 inches. The Wake County building department publishes the required frost depth in its adopted code (IRC Table R301.2).

Does frost depth vary within Wake County?

Very little. Estimates across the county stay within 3 inches. Soil type matters more than location here.