How Do I Choose?
Manhole cover frames are designed to secure manhole covers in place and can vary depending on the surrounding area of the installation. Manhole cover frames can be fabricated in different ways. You may ask yourself – what is the difference between the different styles? And how do I choose which frame is right for my project? Below is a guide to help you better understand the 3 most common frame styles and why you might choose one over another.
Gravel Guard Frame:
Gravel guard frames are the most cost-effective and common option used when installing a manhole cover in a concrete slab. The frame is set on top of level ground or gravel, and concrete is poured around it. The gravel guard, also known as the manhole skirt, keeps the aggregate or debris from falling inside the manhole. The frame may have concrete anchors, to anchor the frame in place once concrete is poured around it. Once cured, the frame is bonded to the concrete, setting it permanently in place. This prevents rotation or displacement. The integrity of the frame and ability to withstand load ratings comes from the concrete. Want to understand more about integrity and load rating? Check out our blog – What Load Rating Do I Need?
Base Flange Frame:
Base flange frames are by far the most universal frame style because they can be installed practically anywhere. Base flange frames can also be cast into concrete slabs, or they can be mounted to the top of a concrete manhole or pipe or on top of any surface. They are commonly used in asphalt applications. Base flange frames may be anchored in place depending on the surrounding terrain. The integrity of the frame comes from the base of the frame, where the bottom flat surface of the base flange bears most of the load.
Top Flange Frame:
Top flange frames are very similar in design to the base flange frame because the integrity of the frame comes from the flange. In this case, the flange is on top and the vertical skirting extends down below the grade of the application as opposed to the base flange, where the vertical skirting extends up above grade.
Top flange frames are usually installed in areas with a precast structure below that requires a manhole cover. These frames can either be casted into place to sit flush with the surrounding grade or they can be used for a quick fix in an existing hole. However, if it is not casted into place, it will not be flush with grade.
Still Not Sure?
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