Underground Electrical
How to Install Conduit Duct Spacers
A step-by-step guide to assembling base and intermediate conduit duct spacers into an aligned duct bank for encased or direct-burial installation — no banding required.
By Innovative Plastics Manufacturing
Conduit duct spacers hold underground conduit in precise horizontal and vertical alignment while a duct bank is assembled and then encased in concrete or direct-buried. Getting that alignment right matters: evenly spaced conduit lets concrete or backfill flow around every duct, keeps the bank from drifting during the pour, and makes future cable pulls cleaner. This guide walks through assembling a duct bank from base and intermediate spacers.
What you need
- Base spacers to set the bottom row of conduit off the trench floor.
- Intermediate spacers to stack each additional row.
- Your conduit (the spacers handle duct sizes from 2” through 8” with 1.5”–3” separation).
- Your project’s duct-bank drawing, which sets the conduit count, configuration, and spacer interval.
For lighter exposed or single-tier underground runs, clip spacers snap directly onto the conduit instead.
Step-by-step
- Set the base spacers along the trench floor at the interval your design calls for — commonly every 5–10 feet and at every coupling. The base lifts the bottom row so concrete or backfill flows underneath.
- Lay the bottom row of conduit into the base saddles, which hold each duct on a precise horizontal grid.
- Snap on intermediate spacers to begin the next row. They interlock vertically and horizontally, so no banding or tie wire is required.
- Build up the bank row by row, keeping spacers aligned vertically so the load transfers straight down.
- Secure against float before an encased pour — anchor or weight the assembly so it does not lift when concrete is placed, then pour and consolidate around the conduit.
Why no banding?
Older duct-spacer systems rely on steel banding to hold the assembly together, which adds labor and a corrosion path. Innovative Plastics spacers are molded from high-impact polymer and interlock mechanically, so the bank is self-locking. That means faster field assembly and spacing that stays consistent through trenching, backfill, and the pour.
Need the bank pre-built? Pre-assembly is available — just ask. For spacing intervals and cover requirements, see our guide to duct bank spacing, and always follow your project specification and the applicable code.
Frequently asked questions
- Do conduit duct spacers need banding or tie wire?
- No. Innovative Plastics base and intermediate spacers interlock vertically and horizontally, so the bank locks together without banding. This speeds assembly and keeps spacing consistent through the pour.
- How far apart should duct spacers be placed?
- Spacing follows your project's engineering drawings, but a common field practice is a spacer set every 5 to 10 feet and at every conduit coupling, so the bank stays aligned during concrete placement or backfill. Always defer to the project specification.
- Can the same spacers be used for direct burial and concrete-encased duct banks?
- Yes. The base and intermediate spacers are used in both encased-burial and direct-burial installations. For direct burial, the spacers hold alignment through backfill and compaction.
