Manufacturer and supplier of roof products and accessories for the metal building industry since 1964

Standing Seam Roof Curb

Standing Seam Roof Curb

The R&S Standing Seam Roof Curb fits any trapezoidal or vertical standing seam roof panel. Curb size and design meet any skylight or rooftop equipment requirements. Equipment curbs have a level top for proper RTU operation. Seam-to-seam (R&S Seam Clip) side flanges come standard for a complete weather-tight seal. Economical flat flange models are also available. 1″ foil-faced rigid insulation comes standard, with optional high R-Value models as needed. Roof curbs may also include an interior liner, duct supports, a damper shelf or custom finish that matches the roof color. The R&S Metal Building Roof Curb installs under the roof panel on the up-slope and over the roof panel on the down-slope, which results in a superior watershed condition. In addition, a 20-Year Warranty comes standard on all aluminum curbs. All curb kits may be ordered with subframe, mastic, sealants and fasteners for a complete install. We offer aluminum or steel construction. MBCI Weather-tightness Warranty approved.

Roof Curbs For: HVAC | Exhaust Fans | Skylights | Gravity Vents | Pipe Penetrations

  • Description
  • Model Guide
  • Sizes & Weights
  • Documents
  • FAQ
  • R&S Insights

Metal Building Roof Curb Specifications

Material Options 0.080 aluminum
18 GA, 14 GA or 16 GA aluminized steel
1″ Rigid Insulation R6.5 (higher R-Values available)
Construction Full penetration welds, thoroughly tested
Mitered corners for true square top
Curb Upslope Flange installs under panel
Closures welded or shipped loose
Integrated 4″ high water cricket
Min 9″ between up-slope curb wall and closures
Curb Downslope Flange installs over panel
Caps (straps) welded or shipped loose
Minimum 3″ down-slope flange
Curb Side Flanges Seam-to-seam, integrates with roof panel
Minimum 3″ between curb sidewall and panel seam
Curb Top Level top for mechanical equipment or as specified
Skylight curbs slope with roof
Dimensions 6″ – 8″ curb height on up-slope (custom heights available)
Finish Options Aluminum mill finish
Galvanized finish
Powder coat (standard colors or custom)
Kynar (exact match)
Accessories 14 GA backer-channel
Sealants, fasteners
Certifications Engineering calcs, stamped submittals (additional costs apply)
Warranty 20 Years (aluminum)
MBCI 20 Year Weathertightness Warranty Curb
1 Year (steel)

Type If Curb (Internally-Flanged)

Typical design for Varco Pruden and Butler roof systems.

Same design / construction with the following exceptions:

Curb Upslope Upslope base flange breaks inward 2″
Includes 2-piece water diverter assembly and backer channel
Curb Downslope Downslope base flange breaks inward 2″
Integrated caps in curb wall accept panel highs
Curb Side Flanges Side base flanges break inward 2″
Backer Channel Backer channel and water diverter assembly Included

Roof Curb Options

Curb Liner Conceals insulation, mill or white finish, complete kit for install
Ridge Mount Installs on ridge condition, double pitched
Collar Top Square-to-round transition
Over / Over Up-slope and down-slope over roof panel
Non-Insulated Cost savings when insulation not required
High R-Value
2″ thick insulation for R14 value (other thicknesses available)
Damper Shelf Damper support for exhaust fan
Duct Supports Blank-offs, duct supports for HVAC equipment
Vibration Iso Rails Vibration isolation rails pre-installed for HVAC equipment as specified

Curb Model Guide

Provide roof panel make, model, seam spacing and pitch when requesting quote.

Model LxWxH Side Flanges Closures/ Caps Upslope / Downslope Curb Top Insulation Material Finish Options
MBS: Standing Seam T: Trapezoidal Seam Clip
V: Vertical Seam Clip
R: Flat Flange
F: Internally Flange
1: Fixed / Welded
2: Loose / Field Located*
3: None
4: Up-slope Flat, Down-slope Offset
* Available on Flat Flange curbs only
U: Under / Over
O: Over / Over
L: Level
S: Slope w/ Roof
Y: Insulated
X: Non-Insulated
A: Aluminum
G14: 14 Gauge Galvanized Steel
G16: 16 Gauge Galvanized Steel
G18: 18 Gauge Galvanized Steel
M: Mill
P: Powder Coat
K: Kynar
CL: Curb Liner
RM: Ridge Mount
FC: Floating 2-Curb System*
CT: Collar Top
DS: Duct Supports
VR:Vibration Isolation Rails
* Inner Curb Dimension


MBS-48x96x8-T1US-YAM-DS-VR: Roof curb for a Standing Seam Roof, 48″ Wide x 96″ Long x 8″ High, Trapezoidal Seam Clip Side Flanges, Fixed Contour Caps with “Under Panel” up-slope condition and “Over Panel” down-slope condition. Curb top flange is sloped with the roof, curb walls are insulated and fabricated of Aluminum with a Mill finish. Kit delivered with HVAC duct supports and vibration isolation rails.


Closure: seals trapezoidal panel at up-slope curb opening (under panel)
Cap: seals trapezoidal panel at down-slope curb opening (over panel)
Trapezoidal Seam Clip (T): side flanges integrate with trapezoidal standing seam roof panel
Vertical Seam Clip (V): side flanges integrate with vertical standing seam roof panel
Layover Side Flanges (R): side flanges extend and layover next natural high rib
Flat Side Flanges (R): flat side flanges 3″ typical
Internally Flanged (F): perimeter base flange breaks / seals inside curb wall
Under / Over (UO): up-slope installs under, down-slope installs over roof panel
Over / Over (OO): up-slope and down-slope flanges install over roof panel
Floating 2-Curb System (FC): Inner weight-bearing curb and outer flashing curb (heavy equipment)
Ridge Mount (RM): Inner weight-bearing curb and outer flashing curb (heavy equipment)
Curb Liner (CL): white or mill finish liner on inside of curb wall; conceals insulationFloating
Collar-Top (CT): square-to-round transition for pipe penetrations

All curbs custom-sized to meet project specifications. Curb weight provided with order.


Additional curb configurations available, call for details

Product Description Model Submittal Specifications Installation Warranty
Trapezoidal Seam Clip MBS-T PDF WORD PDF PDF
Vertical Seam Clip MBS-V PDF WORD PDF PDF
Flat Side Flanges MBS-R PDF WORD PDF PDF
Internally-Flanged MBS-F PDF WORD PDF PDF
Floating 2-Curb System
Trapezoidal Seam Clip
Floating 2-Curb System
Vertical Seam Clip
Floating 2-Curb System
Flat Side Flanges

Curb Sub-Framing (Backer Channel)

Accessories Model Submittal Specifications Installation Warranty
Backer Channel
Trapezoidal Seam Clip
Backer Channel
Vertical Seam Clip
Backer Channel
Flat Side Flanges
Backer Channel
Internally Flanged Curbs

Additional Support Documents

Downslope Loose ContourInternal FlangeVertical Standing SteamPDF

Description Curb Type Roof Type Installation Guide
Downslope Loose Contour Internal Flange Trapezoidal Standing Seam PDF
Downslope Loose Contour Internal Flange Vertical Standing Steam PDF
Curb Wall Section View Relevant to All Curb Types Relevant to All Roof Types PDF

What is the primary purpose of a standing seam roof curb?

Designed to fit trapezoidal or vertical standing seam roof panels, these curbs connect rooftop equipment to the roof.

What materials are commonly used for these curbs?

Common materials include aluminum or galvanized steel.

What are the insulation options with roof curbs?

These curbs come standard with 1″ rigid insulation, with options for higher R-Values available.

How does the roof curb’s construction ensure water doesn’t seep in?

The curbs are manufactured with full penetration welds and features like integrated 4″ high water crickets for effective water diversion.

Is there a warranty on these roof curbs?

Aluminum curbs come with a 20-Year Warranty, while Steel Curbs have a 1-Year Warranty.

R&S Insights Blog

Metal Building Roof Curb – How to Choose the Right Application

There are several choices to make when purchasing a metal building roof curb. Your evaluation should take into consideration the conditions on and around the roof… Learn More

What Are HVAC Roof Curbs and What Are They Made Of?

Commercial buildings often have at least one or a combination of these items on the roof: fans, condensers, skylights, hatches, vents, or AC units… Learn More

What Are Some Uses for Rooftop Curbs?

Roof curbs are used extensively on commercial roofs to ensure the safe installation and proper functioning of various components of the roof system, such as HVAC equipment, and more… Learn More


Check out our Product Line Card

R&S manufactures a wide array of products to fit your project needs. We aim to supply all of your metal building roof accessory needs, not just one product. Why go to multiple vendors when R&S can supply it all?