how to lay electrical conduit in concrete slab

picture showing Decking electrical piping

Decking electrical piping is the process of laying electrical wiring conduit pipes for a house or building, In the slab. This is done before pouring concrete over electrical wire into the slab. I am going to walk you through step by step how to lay electrical conduit in concrete slab.

Materials needed to doelectrical piping in slab.

  • PVC glue
  • pvc electrical conduit pipes
  • Female bushes/couplings
  • Bends
  • Spring bender
  • Spacers
  • Tying wires
  • Loop inboxes
  • Downlight boxes.

Marking lighting and socket outlets points.

The first step in doing decking electrical piping is marking the points where you are going to put your light points, sockets outlets and distribution board.

For you to do this task efficiently, you should have basic knowledge in reading electrical and electronics symbols. Why do I insist that you should have basic knowledge in reading electrical schematics? Engineering drawing is a universal language that electricians, technicians, technologists and engineers use to communicate.

You get the electrical plan layout for the building then you study it. This house wiring piping diagram is going to guide you on the exact points where you have to put your light points and sockets outlets.

conduit pipe drawing

Electrical Pvc looping boxes and bends

Be reminded that you should read the electrical plan layout together with building drawings. Having said that, how do you mark the points. Every electrical slab piping drawing has a scale. You use the scale to locate the actual position of a light point or socket outlet.

Electrical plan layout

Electrical piping drawing

How to use an electrical plan layout to mark light points and sockets outlets.

The first thing to do,you measure the distance of either a socket or light point on the electrical slab piping drawing.

You then transfer that distance to the actual building on the deck. They are basically two ways you can do this. (A)you use a scale rule (B)You calculate using the given scale.

Marking a point using a scale rule is the simplest method that you can use. The important thing to take note of is the scale that is used on the electrical slab piping drawing . You have a common scale-like 1:100,1:75,1:50.

A scale rule will have three scales on it. For example, if the scale on your electrical drawing is 1:100, you look for that scale on your scale rule. Here I must say you measure the distance on the drawing using a scale rule. The scale rule is going to tell you the actual distance on the drawing. This is just like copying and pasting. You copy the distance from the scale rule and paste it on the deck.

Calculating the distance using a given scale. Let’s say you have a scale of 1:100 what does this scale tell you? In simple terms, a 1:100 scale tells you that 1cm on the drawing, is equivalent to 100cm on the ground. Or 10mm on the drawing is equivalent to1000mm on the ground.

Laying pipes on the deck.

Now that you have marked the positions of various light points and socket outlets, It is time to start laying the conduit pipes. Basically, I will talk about lighting circuits, power socket outlets and data socket outlets.

How to lay electrical conduit in concrete slab.

The task that I perform first is to fill all the loop in boxes with wet paper. How do I do this at the time that I am marking the points for light points and sockets, I soak the papers in water. When they were soaked, I fill all the loop in boxes with them. I do this to prevent concrete from getting inside the loop inbox.

When concrete gets in the inspection box in electrical wiring.It can block the pvc electrical conduit pipes. After you are done filling the boxes with soaked paper or whatever material that you want to use.

You place your loop inboxes and down lightboxes in the positions you have marked. Downlight boxes that are specially made to be put in the slab concrete, do not need to be filled with soaked paper. You just have to place them in such a way that they are flush with the decking plates or boards.

When you are done positioning the boxes. You lay electrical conduits in concrete slab, by connecting the conduit pipes to the boxes. Here I must mention that when joining electrical conduit pipes to the loop in boxes, you use PVC glue. This prevents the conduit pipes from coming out of the loop in boxes when pouring concrete.

Laying electrical conduit pipes for the socket outlets.

I have found it easy to lay conduit for sockets outlets by first preparing the pvc electrical conduit pipes. How do you prepare conduit pipes for sockets outlets?

You get your conduit pipes, then you bend them at one end using a spring bender. You bend them in such a way that from the point you have made a bend, the pipe extends out for about 50cm to 60 cm. This is important cause the pipes you have put a bend on, are the ones you will position on the marked points for socket outlets.

Elbows - Special Radius - Heritage Plastics | PVC Conduit | Electrical and  Plumbing
Bends or elbow

If it happens that you don’t have a spring bender, you use elbows or bends. How do you use bends? You position the bends at the marked positions for socket outlets.

After positioning your bends in the correct positions, you start to join pvc electrical conduit pipes to complete your circuit. You use couplings to join the conduit pipes.Do not forget to apply glue when joining the pvc electrical conduit pipes.

I have found out that I get better results when I first apply glue to the conduit pipe then push it into the coupling. They are times when I first applied glue to the coupling then push the conduit pipe.

I discovered that at times the glue fills the whole space in the coupling and blocks the passage making it difficult to wire the circuit.

When you are laying points for data and telephone circuits, the process is the same.

Putting the pieces together.

What do I mean by putting the pieces together? well, I have talked about lighting and socket outlets. How you lay them and join them. There is one thing that has remained. Ensuring that the laid pipes are safe and secure. How do you secure the conduit pipes? On the materials that are needed for decking electrical pipes, I have mentioned that you need spacers and tying wire.

The first step in securing the conduit pipes on the deck is putting spacers along with the entire circuit. Spacers prevent the conduit pipes from being damaged and maintain a proper depth of electrical conduit under concrete. The second step is to secure the conduit pipes by tying them to the steel bars.

What is your experience doing decking electrical piping? Share with me in the comments section below.

how to lay electrical conduit in concrete slab

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