RETROFIT ROOF SYSTEMS
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Our retrofit framing systems satisfy a variety of applications for low-slope, high-slope, special construction, or problematic geometry issues. These framing systems offer design professionals, contractors and building owners a multitude of options that are economically feasible while still maintaining the quality product integrity that is expected from our manufacturer.

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SYSTEM 1
The most common framing assembly for retrofit is the Post and Purlin system. As shown in the following illustrations, the system can be employed for installation over existing roofs with steel or wood framing as well as structural concrete systems.

In this illustration, the system is installed over steel bar joists that are spanning parallel to the new roof slope.






SYSTEM 2
The Post and Purlin system adds a continuous base zee, which enables it to be installed over steel bar joists that are spanning perpendicular to the new roof slope.






SYSTEM 3
For existing buildings with wood framed roofs, the Post and Purlin system uses a continuous base zee installed perpendicular to the existing wood joist. The base zee is required for these types of roofs, regardless of joists’ span direction.






SYSTEM 4
For structural concrete roofs on existing buildings, the Post and Purlin system uses base shoes and posts that are installed centered over the existing concrete beams. When the beams span perpendicular to the new roof slope, a base shoe is still used, dependent on the spacing of the beams in relation to the retrofit purlin’s span capacity. Otherwise, a continuous base zee would be included in the system.






SYSTEM 5
Similar in concept to the Post and Purlin system, McElroy’s Wide-Span framing system offers a unique method for specific applications where the existing roof’s primary support systems are parallel to the new roof slope. In this illustration, a continuous base zee is placed directly over the existing primary framing (beam or load-bearing walls). Adding a continuous zee rafter supported by posts that are installed directly over each existing joist, will enable the new zee purlins to be placed as needed to satisfy design wind and snow loads. This system can easily be designed for purlin spans up to 30’-0” using 6” to 10” deep zee purlins.