Fiberglass Grating Options for Polycast Trench Drain

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Fiberglass is a popular grating option for trench drain.

As the price of stainless steel increases, fiberglass is filling the material gap because of its resistance to corrosion, its high strength, and its easy fabrication.  Also, more people are turning to fiberglass as a alternative grating because it has little secondary scrap value and is less likely than is cast iron to be stolen for recycling.

Molded Fiberglass Grates

Mesh Fiberglass GratingThe molded fiberglass forming method is usually used for making mesh grating and involves a jig that is the size of the desired final product.  Fiberglass thread is arranged and stretched within the mesh shaped wall recesses of the jig before adding a polymer bonding material.  If desired, an abrasive sand-sized material can be applied to the surface at this time to form a non-slip surface.

Molded fiberglass is used for pedestrian and some light traffic applications.  It doesn’t have properties that would allow it to be a drop-in replacement for heavy duty cast iron.  However, a 12″ wide grate of 1.5″ thick molded fiberglass mesh (1.5″ x 1.5″) has the strength to hold a 2830 pound/sq. ft. load.  (See right.)

Pultruded Fiberglass Trench Grates

fiberglass drain covers, fiberglass trench grates, fiberglass trench drains, fiberglass drain gratesFiberglass grating made from the “pultrusion” method (pulling + extrusion) is strong enough to be used in structural applications.  This forming method involves pulling fiberglass reinforcing through an extrusion die, which simultaneously applies binders, heat and protective coatings to the bar or rod-shaped component.  When this method is used for making I-beams, it can rival the functionality of conventional steel.

Pultruded bar grating has potential to replace cast iron grating of the same dimension, though not at the same price. While the grate is strong on its own merits, and the cross members help to concentrate that strength, if a vehicle’s wheels turn too abruptly while on the grating the cross members can be weakened and compromise the grate’s overall strength This can be an issue in some high traffic applications.

For most common trench drain applications, fiberglass grating isn’t required.  Galvanized steel and cast iron grating are the materials of choice when load capabilities are the main grating requirement.  When corrosion resistance becomes the most important design criteria, the materials of choice are stainless steel, high density polyethylene and fiberglass.  Thereafter, the cost and specific details of the application will dictate which material is best to specify.

Fiberglass Grates to fit Trench Drains

Polycast 600 Fiberglass Grating ComparisonHubbell, the manufacturer of the Polycast brand, offers two fiberglass grates that fit their Polycast 500 and 600 polymer concrete channels.  Both grates are bar grating made in the “pultrusion” method and have an added slip resistant top coating.  The difference between these two grates is only in the bar spacing.

The standard fiberglass bar grate, DG0644, has bar spacing on 3/4″ centers which allows it to be used in light automotive applications (Class B).  A heavy duty version of this grate, DG0644SP, uses the same fiberglass bar sections at a 3/8″ spacing.  This tighter bar spacing provides added strength which enables this grating to handle heavier loads (Class C).

For all fiberglass grating, a special locking mechanism is required to keep it secure in the trench drain channel.  This locking device, shown below, is made of stainless steel.  It works by strapping the cross-members of the grate to a center toggle attached to the channel.  Attachment to the cross member keeps the locking device below the surface of the grate and out of the way of traffic above.


Trench Drain Systems (TDS) manufactures a molded fiberglass grateto fit the Polycast and Dura Slope trench drain product lines.  This grating, 4 foot long and 3/4″ thick, has a slip resistant top surface.  And, while it is strong enough to handle light automobile traffic, it is meant for residential use only.  Since it is made from a molded fiberglass, it isn’t designed to be locked down to the channel.  Its uses are best in corrosive or frequent clean-out applications that see only foot traffic, such as kennels or small maintenance facilities.

There are many manufacturers of trench drain.  Trench Drain Systems handles most of them.  Custom fiberglass grating is also available through Trench Drain Systems.  For further information on fiberglass grating and how it can be used in your trench drain application, contact Trench Drain Systems by phone (610-638-1221) or email.

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