What actually governs a roof in this metro, what does not, and which of the things contractors tell homeowners are true. The sources are listed at the foot of the page.
Before you sign with any roofer in Pennsylvania, ask what state and local credentials the contractor holds, get the answer in writing, and check it with the office that issued it. The roof work itself has to meet Pennsylvania's Uniform Construction Code, which adopts the 2021 International Residential Code (34 Pa. Code § 403.21). Permits and inspections run through the municipality that enforces the code, or through a third-party agency or the Department of Labor and Industry where it does not.
These are Township of Upper Allen’s published figures, from the design table in its own building code; the office that issues your permit confirms the figures for your address.
| Criterion | Figure | What it drives |
|---|---|---|
| Ultimate design wind (Vult) | 90 mph | Fastener schedule and the manufacturer wind rating we specify |
| Nominal design wind (Vasd) | 70 mph (derived, not published locally) | The allowable-stress figure older specs quote |
| Ground snow load | 30 psf (set by address) | Structure, and how much the eaves hold in a freeze-thaw |
| Frost depth | 36 in | Footings, not roof covering |
| Seismic design category | B residential | Lateral bracing and structural connections — not shingles |
Vasd = Vult x sqrt(0.6): 90 x 0.7746 = 70 mph. This is a computed conversion, not a figure any jurisdiction here publishes.
The code sets minimums; the shingle manufacturer sets the rest. These are the layers, from the frame up.
This region is assigned seismic design category A–B for houses.
On nailing, the code minimum and the shingle maker's instructions are two different things. The code also points to the maker's installation instructions, and those can ask for more nails than the code minimum, often for the shingle's wind rating; the maker's warranty depends on following them. So the number worth asking any roofer about is the one in the instructions for the shingle being quoted, and whether the quote follows it.
Whether an ice barrier is required is set by the adopted code and each jurisdiction’s own Table R301.2 entry. Most Harrisburg-Carlisle metro jurisdictions do not publish that entry.
Across the three counties on this site, NOAA's Storm Prediction Center logged 21 reports of hail 1 inch or larger from 2016 through 2025, on 14 days; 1 of those reports came in 2025. Each city and county page counts its own. Those are reports from spotters and the public, logged by NOAA's Storm Prediction Center with a location, not a full count, so anyone quoting you a precise “hail events per year” figure for one street is extrapolating.
What matters for your roof is simpler than a statistic: hail damage is often invisible from the ground and obvious from the roof. That is why the inspection is free and photographed.
Each of these pages goes deeper on one job, with the same sources: roof replacement, roof repair, storm damage roof repair, roof inspection, roof ventilation, metal roofing, gutter guards, roof shingles, flat roofing. Every city page adds the permit rule for that city, the code edition where the city or county publishes one, and its own Census housing figures and hail reports.
Free inspection, photographed, and the report is yours either way.
Researched 2026-11-09. Sources: www.pacodeandbulletin.gov · www.pacodeandbulletin.gov · ecode360.com. Rules and staff change; check with the jurisdiction.