How to Pour in Floor Heating Slabs

Concrete is poured over the PEX tubing of radiant floor manifolds to create floor heating slabs. Once the aggregate and insulation of the foundation have been installed, wire mesh is laid down and then PEX tubing is set down over it in a pattern called a manifold. The manifold allows the concrete to be evenly heated and is attached to the wire mesh before the wet concrete is poured. During the concrete pour, one worker has to hold the wire mesh up to ensure that the PEX tubing sits at the correct height in the concrete slab as it sets.

Gravel
Rake
1 inch or 2-inch XPS foam
Concrete floor wire mesh
Rebar ties or plastic zip ties
PEX radiant tubing kit
Air pump with air pressure gauge
Newspaper
1/2-inch plastic angle strips
Concrete floor mix
Water
Wheel barrow
2 shovels
2 helpers
3-foot blunt steel hook with loop handle
Concrete float tools
Concrete trowels

Instructions

- 1
  Lay down a layer of compacted aggregate, such as gravel, for the foundation of the floor base. Use a rake to level out the aggregate. Cover the aggregate floor base with either 1-inch XPS insulating foam if you live in a warm climate, or 2-inch XPS insulating foam if you live in colder climates. Place a layer of the XPS foam vertically along the edges of the foundation wall.
- 2
  Roll out the concrete floor wire mesh and flatten it out. Lay out the PEX radiant tubing in a pattern over the wire mesh according to its packaging instructions. Attach the radiant tubing manifold to the mesh with rebar ties or plastic zip ties. Connect the PEX tubing to the manifold box and use an air pump with an air pressure gauge to pump 50 psi of air into the tubing.
- 3
  Wait overnight. Check the air pressure in the PEX. If it has lost more than 5 psi, there is a leak in the connections of the PEX. Tighten all of the connections. Add more air and wait two hours. If you are still experiencing an air leak, check for punctures in the PEX tubing. Fix any PEX tubing punctures with a repair coupling according to the coupling's packaging instructions. Release the air down to 25 psi.
- 4
  Insert newspaper into the tubing where it enters into the manifold box to protect the copper manifold from accidental overflow during concrete pouring. Install thin plastic angle strips onto the wire mesh to create control joints for the concrete floor. Control joints separate the concrete slab into small sections that can handle the movement of the building foundation as it expands and contracts during the course of the day without developing stress cracks.
- 5
  Mix the concrete with water according to the concrete's packaging instructions in a wheel barrow with a shovel. Tip the wheel barrow's nose towards the ground and have a helper push the concrete out onto the floor with a shovel. Pour a 1 1/2-inch thick layer of the concrete onto the floor. When a quarter of the floor has been poured, have one of your helpers pull up the wire mesh with a 3-foot blunt steel hook with loop handle so that the wire is lifted up into the middle of the concrete layer. This ensures that the PEX tubing is in the correct position in the concrete when it dries. Once you have poured all of the cement, go over it with cement floats and trowels to make the surface as even and smooth as possible.

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