• Constant Hotwater's professionalism, speed, willingness to work with our teams and their assurance of getting it right every time.
  • Constant Hotwater went above and beyond the call of duty and delivered us a spanking underfloor heating system with minimal fuss.
  • Boys & Girls Nursery would highly recommend Ian from 'Constant Hotwater' for any underfloor heating job.
  • Constant Hotwater have an excellent knowledge of underfloor heating they work fast and efficiently and was by far the best quote we had for the job.


There are two types of floor construction that underfloor heating can work with.

  1. Solid floor construction
  2. Timber suspended

Our heating system can be fitted in both concrete and timber suspended floors. For other floor constructions please contact us. For example we also offer a floating floor solution.

Concrete Floors

In concrete screeded floors, the screed acts to diffuse the heat across the surface providing an even temperature at the floor surface.

Depending on the type of building and the construction there are a number of methods of laying the underfloor heating pipes in concrete floor structures.

The most popular method of installation is as follows:

A concrete slab (or suspended beam and block construction) is laid over a damp proof membrane. A 20mm thick piece of insulation is fixed to the perimeter (external) walls, to a height to include the depth of floor insulation and screed.

Whilst the edging insulation may be on show it is covered by wall plastering and skirting boards.

Floor insulation is laid to the whole area, joints are taped to prevent the ingress of screed between the insulation boards. The floor is now ready for the underfloor heating pipework installation.

We recommend you use a minimium of 50mm layer of Polyurethane insulation. We recommend Polyurethane as it out performs Polystyrene and its greater density allows use of clip fittings. All insulation requirements needs to comply with the current building regulations.

Finally 65 – 75 mm screed is laid on top of the insulation and the pipe.

If you use polystyrene insulation (50mm) it is recommended that you install wire mesh on top of the insulation and tie the pipe to the mesh.

Timber Suspended Floors

Timber suspended floors do not conduct heat as efficiently as screeded floors. This means that the heat output is less.

Our system is very simple and easy to install in timber suspended floors. The system is based on hundreds of installations that are now working with total satisfaction.

Between the joists, a 50mm polyurethane insulation board is cut for a tight fit.

The pipe is then clipped on the insulation

To get the timber suspended floor to act as a screeded floor and to give out more heat, the air gap between the insulation and the floor boards should be filled with a lightweight screed mix.

Pipe Construction

Multilayer pipe systems now offer the most comprehensive range of plumbing and heating systems available.

Used extensively throughout Europe, multilayer pipe is both flexible and formstable. Its enclosed aluminium pipe ensures that multilayer pipe is 100% oxygen diffusion proof while maintaining very low expansion rates similar to other metal pipes.

The pipe we use is one of the best quality pipe on the market – this is the multilayer pipe made of PEX/AL/PEX. The pipe is 100 % oxygen diffusion tight, therefore offers total protection against oxygen entering the heating system. The pipe is approved for 10 bar pressure and 95 degree C temperature – one of the highest settings available. Your system will never need the above settings, but it indicates the strength of the pipe.

The inner and outer polyethylene pipes prevents scaling and corrosion and its unique combination of butt-welded aluminium and crosslinked polyethylene ensures that multilayer pipe is the only alternative to copper. Multilayer Pipe gives the installer the advantages of both metal and plastic.

Offered with fittings ranging from standard compression to the superb “Press-fit” system, multilayer pipe brings new and genuine improved standards to installation techniques. Currently available in 6 sizes, multilayer pipe is now the first genuine pipe for all applications, be it plumbing, heating, underfloor heating or mains supply.

  1. Outer pipe in electron-beam crosslinked polyethylene.
  2. Sandwich layer homogeneously joining the outer pipe to the aluminium pipe.
  3. Uniform longitudinally welded, perfectly round, 0.4mm thickness aluminium pipe.
  4. Sandwich layer homogeneously joining the inner pipe to the aluminium pipe.
  5. Inner pipe in electron-beam crosslinked polyethylene

Why Multilayer Pipe?

There are 10 reasons why multilayer pipe is the best available pipe for underfloor heating:

  1. Butt-welded aluminium pipe.
  2. 100% oxygen-tight and water vapour diffusion tight.
  3. Low coefficient of linear expansion.
  4. Entirely corrosion-resistant, also against chemicals and electrochemicals.
  5. Sound-insulation similar to entirely plastic pipe.
  6. Electro-beam crosslinked inner and outer pipe.
  7. High resistance to pressure and temperature.
  8. Smooth surface, less loss of pressure.
  9. Light as plastic piping.
  10. Flexible, easy to bend even at low temperature, retains curved shape.

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