Commercial Gutters & Drainage
Oversized box gutters, internal drainage, scuppers, and custom sheet metal for large commercial roofs
Commercial drainage is engineering, not just metalwork. A typical commercial roof sheds thousands of gallons in a heavy rain event, and the gutters, internal drains, scuppers, and downspouts that move that water are the difference between a dry building and a liability claim. National Restoration designs, fabricates, and installs commercial drainage systems sized to real storm intensity, built from heavy-gauge materials, and detailed for the way commercial buildings actually perform.
Our sheet metal shop fabricates custom box gutters, scupper collection heads, conductor boxes, and oversized downspouts to match any architectural vision. From big-box retail to industrial distribution centers to historic commercial buildings, we deliver drainage that protects the building envelope and the site around it for decades.
Why Commercial Drainage Is Different
Residential gutter methods do not scale to commercial volumes and spans. Here is what commercial-grade drainage requires.
Drainage calculations per SMACNA and the International Plumbing Code using local 100-year rainfall intensity. Gutter, leader, and drain sizes that handle design storms without overflow.
.040 to .063 aluminum, 24 and 22 gauge steel, copper, and Galvalume. Proper material weight for span, thermal movement, and ice load. No thin residential-gauge metal on commercial buildings.
On-site roll-forming for continuous runs, shop-brake fabrication for box gutters and conductor heads, and architectural custom profiles when the design calls for it.
Expansion joints at the right spacing, properly soldered or riveted seams, through-wall scuppers flashed to the roof system, and ice-dam protection where climate demands.
Gutter and drainage details coordinated with TPO, EPDM, PVC, and modified bitumen roof systems for warranty-compliant integration. Single-source accountability on roof and drainage.
Scheduled drain cleaning, strainer replacement, and seasonal ice management. Preventive programs that stop clogs and overflows before they become interior water claims.
Commercial Drainage Components
A complete drainage system requires every component sized, specified, and installed to work together.
Custom-fabricated box gutters from 6 inches to 24 inches wide, with depths engineered to move the design storm flow. Soldered, riveted, or sealed seams. Proper slope and expansion joints.
- Kynar-finished aluminum, copper, or steel options
- Hidden bracket mounting systems
- Overflow scuppers sized to code
Primary and overflow internal drains sized per IPC. Dome strainers, drain insulation, clamping collars correctly integrated with the roof membrane for warranty compliance.
- Cast-iron and aluminum drain bodies
- Secondary overflow drains at independent outlets
- Electric drain heating for freeze-prone climates
Through-wall scuppers with properly flashed collars, architectural conductor heads (leader boxes), and splash transitions. Decorative and functional elements on historic and architectural buildings.
- Custom copper and zinc conductor heads
- Through-wall scupper flashing to roof warranty
- Overflow scuppers per IPC 1108
4 inch, 5 inch, 6 inch round and rectangular downspouts, sized per roof area and design storm. Properly strapped, offset around obstructions, and terminated into site drainage.
- Cast-iron boot transitions at grade
- Impact guards at loading docks and traffic zones
- Connection to storm sewer or site drainage
Drainage Project Delivery
A structured process that moves from hydraulic calculation to installed and tested drainage.
Tributary roof areas identified, local rainfall intensity looked up, and gutter and downspout sizes calculated to code. Existing failures documented.
Shop drawings show gutter profiles, hanger spacing, expansion joint locations, scupper dimensions, and downspout routing. Issued for owner and architect approval.
Box gutters, conductor heads, scupper liners, and transitions fabricated in our sheet metal shop from heavy-gauge material. Soldered or sealed per specification.
Gutters hung to proper slope, scuppers through-wall flashed, downspouts secured, drains integrated with the roof membrane per manufacturer detail. All trade coordination in-house.
Gutters flooded and drainage verified. Owner turnover documents include drain locations, cleaning access, and recommended maintenance intervals.
Drainage Upgrades on Existing Buildings
Many commercial buildings operate with drainage that was undersized when built and is now failing after decades of heavier storms. Overflow at gutters, saturated walls below scuppers, and recurring interior leaks are all signs of an undersized system.
We retrofit drainage on occupied buildings: larger box gutters, added scuppers, upsized downspouts, and code-compliant secondary overflow. Owners see interior leaks stop and insurance claim frequency drop.
Request Drainage AssessmentEngineered Drainage, Built for Commercial Storms
Oversized box gutters, internal drainage, scuppers, and custom sheet metal. Sized to code, built in our shop, and installed by commercial crews. Start with a free drainage assessment.