Roof Hugger provides general instructional information to assist in the proper installation of Roof Huggers on projects where new roof panel will meet all local wind, snow and seismic loads at existing purlin spacing. If you have any questions please contact Roof Hugger prior to any installation. If a project requires job specific engineering refer all installation and detail questions to the project engineer.

Hugger Installation Info

Please reference our DOWNLOADS page for construction details, specifications, testing, and other usable documents.



To determine the lineal footage that you may need, use this simple formula: 

For a given slope, you divide the width of the slope by the spacing of the existing purlins, and be sure to add 1 for the eave strut. Now multiply that by the length of the eave, and that will give you the lineal footage for that side of the building.

 If it’s a mono slope you’re all set, if it’s a gable, you usually can double your answer, however always double check the other sides purlin count.

All other roofs, it’s time to get some paper and draw it out.


If you are bidding a metal roof retrofit, and you’re not sure if you need to include engineering in the quote, here are a few building situations and locations that will let you know to include engineering.

In the state of Florida, engineering is required on all new metal roofs. Around the country engineering is usually required with all state and local government owned buildings, all schools, military installations, buildings located near open water, or high wind hurricane or tornado zones. Engineering can be required in areas with heavy snow loads too.

Roof Hugger will estimate the wind and snow loads for your project at no charge, if requested. Our proposal will include the material we think is needed to comply with the current building codes. We are not an engineering firm, our third-party engineer handles all finished designs, and our estimated design and pricing will be subject to final engineering review.


There are a number of ways that existing metal roofs have been and still are being retrofitted. Many of these methods cannot be considered structurally correct sub-framing systems. They lack the ability to withstand wind uplift and therefore are subject to failure. Roof Hugger sub-framing systems have been installed on over 100 million square feet of existing metal roofs and continue to be installed on approximately 6 million square feet annually. Our systems have withstood hurricane force wind loads from Katrina, Ike and others without a single failure. This is a testament to our systems that they are safe and structurally correct. This is the primary reason why Roof Hugger is the most specified metal-over-metal sub-framing systems by building owners nationwide including federal and state governments, the military and schools. Below are some of the other methods which we have listed their challenges.

Because of the width of the hat section, only one screw can be installed into the existing purlin. The other screw is attached to the existing 26 to 29 gauge metal, which does not provide sufficient pull-out strength.

Sitting on top of the existing ribs requires a long attachment screw and when exposed to thermal movement, they will “rock” back and forth causing fastener back out and ultimate failure.

Roof Huggers provide a positive connection directly to the existing purlins made available by our factory punched and nesting design.

For the same reasons as #1

Quantity of fasteners for the new metal roof must be increased due to the much reduced pull-out strength into wood, increasing installation labor and material costs.

Pressure treated wood is corrosive when placed in contact with existing and new metal roofs.

If 18 – 22-gauge hat sections are used in lieu of wood, as shown in the above isometric view, these members have a low pull-out strength, reducing system capacity. When used with 16-gauge or heavier, high strength members, the system is still not suitable for through fastened (screw-down) metal roof as they are too rigid for long panel runs to allow for expansion and contraction.

Roof Huggers are made from minimum 16-gauge, grade 50 steel and are Zee shaped, allowing for expansion and contraction like the existing purlins.

Frequently it is necessary to reduce the purlin/clip spacing in the corners and edges of the existing roof to meet current codes. Stand-off clips systems are challenged to withstand the increased wind loads in these zones and often must add purlins under the existing roof to provide the correct clip spacing.

Roof Huggers can be designed with additional sub-framing attached on top of the existing roof, specifically engineered to reduce the existing purlin spacing and properly support the new panels to meet the new wind/snow load requirements.

Most coatings are quick fixes that fail to permanently fix the existing roof.

Preparation of the existing roof is vital to the coating’s adhesion and performance.

They do nothing to comply with new stringent Building Code wind speeds or snow loads and may hide deficiencies.

Roof Huggers provide you with a way to attach a new metal roof with a 50-plus year service life that can meet all current code requirements.

Read more about coatings:

TPO systems have become popular recently since they are slightly less expensive than Metal over Metal Systems.

Design and attachment is critical however. In order to meet existing wind loads the TPO must be connected to the existing purlins per the manufacturers approved and tested details. Systems that are attached only to the existing roof panels, will not comply with the codes.

TPO systems must not allow water to accumulate on the roof surface or overloading and potential collapse is possible (see photo).

TPO systems do nothing to add strength to the existing roof to meet the new code requirements for snow drifting they just add weight.

TPO systems have about half the life span of metal roofing systems, making their slight initial cost advantage a very poor investment.

Roof Huggers provide you with a base for a new long-life metal roof that can comply with all new wind and snow loads. Huggers also create a cavity that can be used to add insulation for increasing the buildings energy efficiency.

Read more about TPO systems:

Roof Hugger sub-purlins are specifically designed to fit over any existing metal roof system.

They are much faster, less complex and less expensive than removing and replacing an old metal roof.

They can be made to a specific height for adding insulation or removing steps in roofs that have created poor weather tight roof connections.

They can add strength to the existing purlins to overcome the additional weight of the retrofit.

They can be designed to allow the new roof to comply with todays stricter building code requirements.

Roof Hugger is the most tested retrofit sub-framing System available. They are made from high strength 16ga. (0.060 min.), 50 ksi, G-90 Galvanized steel.

They will allow an existing screw-down metal roof to be upgraded to a standing seam roof without a major engineering analysis and upgrading the existing purlin bracing to make up for the removal of the diaphragm strength provided by the old roof panels.

Roof Hugger products are made in the USA


Roof Hugger Animated Installation Video

This video, of course, is an Artist’s rendered view of how simple Roof Huggers are installed. It illustrates the sequence of installation from installing our sub-rafters that are commonly included for wind uplift conditions in the corners and edges of the roof. These are not always required, but Roof Hugger will determine their need based on a preliminary design using your chosen new roof system’s E1592 test results. Then the eave Hugger is installed working your way up slope to the primary Huggers over the existing purlins and adding intermediate Huggers between the existing purlins. Our sub-rafters allow these intermediate Huggers to securely fasten to the new roof’s sub-framing system and satisfy building code required wind requirements. Insulation is installed during the new roof installation process if the building owner and roofing contractor chooses to include it. Installation of a Roof Hugger Metal-over-Metal Retrofit sub-framing system is Safe and Easy to understand.

E 1592 wind uplift testing over roof hugger sub-purlins

A short video to illustrate the negative pressure testing of a 16″ wide x 2″ tall vertical rib standing seam roof installed over Hugger sub-purlins attached to a simulated existing 12-inch O.C. “R” or PBR-Panel metal roof.

Video Location: Force Engineering & Testing Laboratories in Humble, Texas

Roof Hugger stands ready to discuss your metal over metal retrofit project and the design process.  If at any point during the design process or the installation process you have a question or concern reach out to us.  Our goal is to make sure you do not run into any problems from design to installation.

You can contact us via email:

Or call us at Call us at +1800-771-1711“>1-800-771-1711.