Retrofit Roofing Systems
Is my building a good candidate for retrofit?
Buildings are designed to carry loads in a specific manner. For instance, a building may be designed to carry heavy live loads distributed over a flat roof area. If you erect framing and build a sloped roof on top of the flat roof, you introduce greater lateral loading to that structure. Also, if a roof has many rooftop units that will remain in place and in operation then retrofit may not be your best solution. In many instances, mechanical equipment can remain in place and enclosed within the retrofit cavity with proper overhead spacing and calculated ventilation methods incorporated into the design. Often times, units can be raised to the new roof framing with proper support and aluminum curbs. Retrofit is, more often than not, a wonderful solution in achieving long term weathertightness in your roofing system. In the end, a structural engineer will need to determine if the existing building framing can accept the proposed retrofit design.
Are all engineered retrofit systems equal?
It is best to answer this question by asking other questions. How is your system engineered? What specific criteria and testing do you consult to design your system? Do you fully adhere to and meet UL (United Laboratories) construction methods? Do you conduct fastener pull out testing on the existing roof to determine how the new roof system framing will attach to the existing roof framing and not just the deck? If so, will you tell me what type of anchorage the system will need, how many connection points, and what type of reactions your system will impose on the existing structure? Do you consider the compressive strength of existing insulation materials? There are many other things to consider to ensure your retrofit roof system will safely and effectively perform for the long term.
How important is ventilation and insulation in a retrofit system?
Building a slope on top of a flat roof will create an air cavity. It is highly recommended to provide adequate ventilation in this situation. Equipment requiring combustion air and necessary air exchanges need to be considered when calculating ventilation requirements. A design professional will know minimum requirements and also mandates as stated in the NFPA building construction and safety code.
Most older buildings are not adequately insulated. Retrofit allows the opportunity to add insulation and increase thermal efficiency. Proper insulation placement and type depends on multiple conditions. Government energy credits may also be available.
Gable Retrofit over Barrel Design Building
Gable retrofit design over an older barrel building is a good, economic solution for long term weathertightness.
Gable Retrofit over Flat Roof System
Gable retrofit design over an existing structure with a flat roof changes it to a fully water shedding system. All roofs are designed to drain water, unfortunately, ponding in some measure, is often a reality for flat roofing systems. Over time, this can prematurely wear out the membrane, plys and associated components in general.
Radius "Barrel" Retrofit over Flat Roof System
Gable retrofit design over an existing structure with a flat roof changes it to a fully water shedding system. All roofs are designed to drain water, unfortunately, ponding in some measure, is often a reality for flat roofing systems. Over time, this can prematurely wear out the membrane, plys and associated components in general.
Additional Retrofit Configurations
Increased Roof Slope
Existing buildings can be retrofitted to achieve a steeper roof slope than what is existing. This may be due to a great water shedding capability or possibly to achieve a certain store front configuration and aesthetic.
Addition with Valley Gutter
Additions that result in a valley gutter condition often results in problematic leaks and a retrofit framing system to eliminate this condition is a good solution.
Mid-Slope Step Down
Overcome weathertightness issues, improve overall aesthetics or change the end use capabilities of the existing structure. Retrofit to eliminate this condition is a viable solution.
Reverse Slope Retrofit
Reversing the roof slope of a building may be smart if the usage needs of the building changes whether it be exterior or interior focused.
