Base & Intermediate

A conduit duct spacer is a two-piece interlocking support that holds underground conduits in precise horizontal and vertical alignment while a duct bank is trenched, encased, and backfilled. Base and intermediate spacers are two halves of the same system, and they work together. The base spacer sits on the trench floor as the bottom course, cradling the first row of conduit and establishing the spacing pattern for everything above it. Intermediate spacers then stack on top, locking into the base and into each other to add row after row until the duct bank reaches its planned height. Innovative Plastics offers duct spacers trusted by contractors for decades, featuring a proven design that supports duct arrays during trenching prior to encasement and remains securely in place under worker weight and during backfill operations.

The spacers interlock both vertically and horizontally, which is the practical reason no banding is required. Each piece keys into its neighbors, so a fully built bank behaves as one rigid assembly rather than a stack of loose parts. Building a row at a time, a crew lays a course of base spacers, drops in the conduit, snaps intermediate spacers over the top to capture that row and form seats for the next, and repeats. Because the geometry is fixed by the spacer rather than by a worker’s eye, the array keeps consistent separation from the trench floor to the top course, with no field measuring between conduits and no straps to cut, tension, or re-check. For step-by-step assembly and spacing guidance, see our guide to installing conduit duct spacers and our explainer on duct bank spacing.

Available in eighteen sizes accommodating duct diameters from 2 inches (50 mm) to 8 inches (200 mm), with separation distances from 1.50 inches (40 mm) to 3 inches (80 mm), the line covers the conduit separations specified for most underground electrical and broadband banks. The same spacers serve both encased burial, where the assembled bank is surrounded by a concrete pour, and direct burial, where the conduit is laid in the trench and covered with backfill. Manufactured using premium high-impact polymers and advanced production methods, the spacers resist extreme temperature variations and UV exposure, and each lot meets strict consistency standards for precise duct separation. Pre-assembled configurations are available upon request.

For an encased pour, securing the bank against float matters: liquid concrete is far denser than the conduit it surrounds and will try to lift the array unless it is anchored to the trench floor or weighted down before placement. Because the interlocking spacers tie the whole bank together, the assembly can be staked or tied as a unit and holds its alignment through the pour. Also known as conduit chairs, duct bank spacers, or trench spacers, base and intermediate spacers anchor our Duct Spacers line. For lighter single-tier runs, where a full base-and-intermediate stack is more than the job needs, see our lighter clip spacers.