Johnson County, KS Roof Snow Load - 20 psf
Johnson County, KS roof snow load, translated
A typical heated home in Johnson County is designed to carry 20 pounds per square foot of snow on its roof, per ASCE 7-22. ASCE 7's low-slope-roof minimum (§7.3.4) raises the governing figure to 20 psf - higher than the 14 psf the ground-load formula alone would give, and the code says use the larger one.
On a roof that means 44 in. of fresh snow, 16 in. once it packs down, or 4 in. of solid ice - three very different piles for the same load. A meaningful design load. Most homes built to modern code handle it, but additions, carports, and flat-roofed sections are worth a second look.
Johnson County at a glance
- Design roof snow load20 psf
- Ground snow load, ASCE 7 map20 psf
- National rank#529 of 2,758
- Kansas rank#1 of 105
- Population632,276
- Annual snowfall, NOAA normal13.8 in.
- FIPS20091
Where Johnson County ranks
#1 of 105 Kansas counties by design load, top 19% of 2,758 nationally - that's Johnson County's spot. 18.2 psf is Kansas's typical county figure - Johnson County beats it by 1.8 psf.
FIPS 20091, population 632,276, centered near 38.8839°N 94.8223°W. ASCE 7's underlying ground snow load here is 20 psf before the code's exposure and importance factors bring it to the 20 psf design figure above.
Johnson County: average annual snowfall
Johnson County sees about 13.8 in. of snow most winters, per the OLATHE 3E, KS US station's 1991-2020 NOAA normal. See the density guide.
Read this before you use Johnson County's figure
The figure above assumes the case ASCE 7-22 treats as typical: a heated, ordinary-occupancy home on a partially exposed site. Change any of those - exposure, heating, roof pitch, occupancy category - and the real design number moves.
A building permit needs the number at your exact address, not the county average - the free ASCE 7 Hazard Tool returns that from your coordinates in about a minute and produces a PDF a plan reviewer will accept. Details: the calculation guide.