For Architects and Specifiers
Everything you need to specify a metal-over-metal retrofit
A metal-over-metal retrofit puts a new metal roof over an existing one on retrofit sub-framing, without tear-off. TopHat provides the specification, details, test data and project engineering to put it in your project manual. New to retrofits? Start with the reroofing guide.
Specification
- Guide specification: Section 13 34 21, Retrofit Steel Roof Framing System, in Word and PDF, in the document library. The same text is also available numbered 05 46 00 for project manuals that keep retrofit framing in Division 05.
- Other sections: depending on how your project manual is organized, the work can also sit under Division 07 roofing sections. See the CSI division options in the document library.
- Delegated design: retrofit framing is normally designed by a professional engineer for the project's loads. TopHat can provide an engineering and shop drawing package; require PE-sealed calculations in the submittals.
Details and product data
- Standard details in PDF and DWG, over R-Panel, 7.2 Rib, 7.0 Rib, UltraDek and standing seam.
- Product pages: TopHat Subframe (hat section; also strengthens purlins), Zee Strip (notched zee), Deflection Limiter (closer attachment in edge and corner zones).
- AISI base test reports and what they mean.
- Energy savings from insulating the cavity between roofs.
Writing an equal-friendly sub-framing spec
Naming one product with "no substitutions" removes price competition from the bid. Listing the performance you need, with a basis of design and "or equal," keeps the standard high and lets bidders compete. Characteristics worth listing:
- Fits the existing panel profile (notched or punched to the ribs) without crushing the existing roof.
- Minimum steel gauge, minimum yield strength and galvanized coating class.
- Attachment through the existing roof into the existing purlins, with fastener type and spacing per the engineering.
- Project-specific calculations sealed by a professional engineer licensed in the project's state.
- Test reports supporting any capacity values used in the design.
- Field fastener pull-out testing, if the existing purlins' condition is uncertain.
If your spec already names another sub-framing brand, see how "or equal" substitutions work.
Training
The MBCEA / MBI retrofit training video explains the types and methods of retrofit over existing metal and flat roofs. See also the video library.
Specifying a retrofit?
Send the project, existing roof profile and loads; we will help with the spec section and details.
Contact TopHat