Prefabricating Conduit Arrays Outside the Trench

Building a conduit grid piece by piece in a muddy excavation is slow and hard to keep square. Many electrical and civil crews prefer to assemble the array on the surface, then lower it into the trench before the concrete pour. Custom CNC-cut HDPE duct bank spacers from Blue Ridge Thermoforming (BRT USA) are built for that workflow: hole centers are already in the sheet, so the crew is locking conduits into a finished grid rather than inventing one underground.

Assemble on the surface, then lower

The board is a flat HDPE sheet with the hole pattern from your conduit schedule. Crews slide conduits through the holes (or place the sheet over a staged conduit set, depending on means and methods), build the full array length needed for that lift, and lower the assembly into the excavation. The boards hold rows and columns through the concrete pour.

BRT does not publish a labor-savings percentage. The value is operational: geometry is set before the trench, not rebuilt under time pressure at the bottom of the dig.

Spacing along the run

Spacer boards repeat along the duct bank. Typical intervals are every 4-7 ft, per the civil package. Call out the interval when you quote so quantity and staging match the pour sequence. Too few boards and the array can wander between supports. Too many and you add handling without changing geometry. The civil note owns that decision; fabrication follows it.

Set spacing before the trench

Because center-to-center spacing is cut into the sheet, the crew is not measuring every hole in the excavation. Mixed conduit sizes stay on their drawn centers. Flow holes, rebar holes, and a ground-wire hole appear only where the print calls for them, so concrete and steel pass where engineering expects.

That is the difference from stacking molded catalog chairs that force a fixed grid. Prefab with CNC sheet means the prefabricated array matches the stamped section, including non-catalog layouts common on data-center primary service, feeder, generator, and fiber banks.

Staging and just-in-time delivery

Boards leave Greenville, SC for the jobsite. Just-in-time shipping and offsite warehousing are available when the job needs boards staged week by week or pad by pad. Long campus runs often use repeating board types: quote those as line items with quantities per section type rather than as one undifferentiated pile.

Plant context for planners and PMs:

• In-house 5-axis CNC routing of HDPE sheet
• Typical thickness 3/8 in and 1/2 in
• Address: 184 Commerce Center, Greenville, SC 29615
• ISO 9001:2015 quality system
• Southeast jobsite deliveries, including SC, NC, GA, TN, and VA corridor work

How this fits the pour sequence

A simplified field sequence looks like this (means and methods vary by contractor):

• 1. Confirm board type against the duct section for that pour segment
• 2. Stage boards and conduit near the trench, not in it
• 3. Assemble the array on the surface using the CNC hole pattern
• 4. Lower and set elevation / alignment per the civil detail
• 5. Place remaining rebar and forms as required
• 6. Pour; concrete flows through any flow holes cut on the print
• 7. Repeat with the next boards at the specified interval along the run

The spacer stays in the bank. It is encased with the conduits. It is not a temporary form that gets pulled later.

Custom conduit spacers, not a trench puzzle

Each board is a custom array: conduit sizes, row and column count, and center-to-center spacing from your schedule. That is what makes surface assembly predictable. The crew is not improvising hole locations with a tape measure at the bottom of the excavation. Mixed-size banks (power plus fiber or control) stay on their drawn centers when the sheet carries every OD.

Contrast with molded catalog chairs: those products work when the bank matches a stock module. Prefab with chairs still means accepting the chair’s grid. Prefab with CNC sheet means the prefabricated assembly matches the stamped duct section, including flow, rebar, and ground openings when specified.

BRT’s public copy is careful on labor claims. We describe the workflow. We do not publish a labor-savings percentage. Estimators should use their own production rates.

FAQ

Do you supply molded interlocking chairs for prefab?

No. BRT cuts custom CNC HDPE sheet arrays from your drawings and conduit schedules. Molded catalog chairs are a different product.

Can we prefabricate mixed power and fiber banks?

Yes, when the drawing calls for a mixed bank on one sheet. Provide center-to-center spacing between power and communications conduits. BRT cuts that spacing; we do not assign an EMI clearance.

What should we send for a prefab-oriented quote?

Drawing or conduit schedule, thickness preference, flow/rebar/ground requirements, spacing interval along the run, quantities by board type, and whether you want jobsite or warehouse staging. Start from the duct bank spacers page for the full options table.

Custom HDPE duct bank spacers · Data center duct bank spacers