Macoupin County, IL Roof Snow Load - 20 psf
Macoupin County, IL roof snow load, translated
A typical heated home in Macoupin County is designed to carry 20 pounds per square foot of snow on its roof, per ASCE 7-22. §7.3.4's low-slope minimum of 20 psf is what actually governs on a flat or low-pitch roof here - higher than the 14 psf the base ground-load formula gives.
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.
Macoupin County, IL: quick facts
- Design roof snow load20 psf
- Ground snow load, ASCE 7 map20 psf
- National rank#764 of 2,758
- Illinois rank#30 of 102
- Population43,895
- Annual snowfall, NOAA normal16.5 in.
- FIPS17117
Where Macoupin County ranks
#30 of 102 Illinois counties by design load, top 28% of 2,758 nationally - that's Macoupin County's spot. 19.3 psf is Illinois's typical county figure - Macoupin County beats it by 0.7 psf.
FIPS 17117, population 43,895, centered near 39.2659°N 89.9263°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.
Macoupin County: average annual snowfall
Macoupin County sees about 16.5 in. of snow most winters, per the CARLINVILLE, IL US station's 1991-2020 NOAA normal. See the density guide.
Read this before you use Macoupin 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. (How this figure is calculated.)