Special junction box to cap end of utility conduit. Workshop Connectivity:

Making A Non-Electrical
Junction Box From Plywood

In This Article:

A rectangular box is built from plywood. A large hole is drilled in one end and a modified PVC pipe coupling is used to secure the box to the conduit.

Related Articles:
Skill Level: 2 (Basic) Time Taken: About An Hour

By , Editor



Two years ago I installed a four-inch white PVC drain pipe between the garage and the basement.

The purpose of this pipe is strictly for carrying non-electrical utilities, such as compressed air, telephone, computer network or speaker wires.

In the same trench I also installed a two-inch gray PVC electrical conduit between the house and garage.

PVC pipe used for special conduit between house and garage.


Electrical conduit is always terminated with some sort of junction box, so I decided I should make something similar for this utility conduit.

I suppose I could just leave this conduit with no box covering the end, but I can think of several advantages to covering it . For starters, some building codes may require such a conduit to be closed off to keep air from moving between the garage and the house. There could be problems with automobile exhaust getting into the house, or the conduit could allow smoke from a garage fire to enter the house.

In the winter I could feel a LOT of cold air pouring out of the pipe into the basement. Simply taping a piece of plastic wrap over the end of the pipe reduced this problem.

But the real reason I needed a box to cover the ends of this conduit is much more sinister. I'll describe this at the end of the article.


Conduit pipe through garage floor slab. The white pipe is the 4 inch PVC pipe that we had installed a couple of years earlier. This pipe goes straight down about a foot below the floor and then turns away from the garage using a long-radius elbow.

This pipe is buried about 18 inches below the ground, and penetrates the basement wall of the house, about 15 feet away.


Using a hole saw, I cut a 4½" diameter hole in a piece of plywood.


This piece of plywood is about 7½" square. I placed the plywood over the pipe to make sure it fit.

I cut the hole so the plywood bottom would be about ½ inch away from the wall.


On a band saw, I cut off part of a 4 inch PVC coupling.

I could have also used a hack saw for this operation.


I marked the location of the plywood on the end of the 4 inch pipe. Then I dabbed some PVC pipe cement on the pipe, just below the point where I wanted the plywood bottom to be.


I slipped the coupling down over the end of the pipe, but I was not able to get the ring of plastic down far enough before the glue dried.

In hindsight, it would have been smarter to cut through the ring, so it could expand easily and slide over the pipe.


I made this box from ½" plywood. I glued and stapled the sides together.


I placed the box over the end of the conduit. The PVC ring keeps the box from sliding down.


I screwed the box to the wall.


I put the other ring in place, but I decided not to glue it. If I need to, I'll glue it later.


I drilled a 3/4 inch hole for this air hose.


I fastened the cover with short flat-head screws.


The completed "junction box". This box is 7½" square on the inside, and about 14" tall.

I chose this size because I had scraps of plywood close to those dimensions.

I also built a similar box at the other end of the conduit, just inside the basement wall.


Further Reading:



Tools Used:

  • Cordless Drill/Driver
  • Basic Carpentry Tools
  • 4½" Hole Saw
  • Heavy-Duty Drill
  • ¼" Crown Pneumatic Stapler
  • Band Saw (or Hack Saw)

Materials Used:

  • ½" Plywood, Assorted Scraps
  • 7/8" Stapes
  • Flat-Head Wood Screws
  • PVC Pipe Coupling
  • PVC Cement

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Written February 1, 2006