Can the height of the floor structure with the ventilation ducts and the heating system be 150 mm?

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For our new building, the contractor proposes a floor construction of 190 mm.

An independent architect confirmed to us that in the past he had planned and built his floor construction using 150-160 mm. His calculation is as follows:

Concrete floor. 50 mm of insulation, with room for ventilation ducts (50 mm high), supply and return, fresh water and electrics. Filling with perlite filler. 20-30 mm insulation (impact sound). 20 mm for underfloor heating. 45 mm for screed. 15 mm for flooring. Makes a total of 150-160 mm.

Since we are limited to the maximum height of the building, we would like to remove every inch from the floor to add to the height of the room. In our layout, the sewer pipes will not go through the floor, but directly in the drywall floor below or in the basement.

Can you confirm or refute the above floor thickness calculation with your experience?

  • What kind of basement is under the floor you describe? If it is not insulated, then you need to use good insulation to make it 50mm thick. 
  • @Burke The basement under the first floor is also insulated and heated.
  • I wouldn't do it because of the difference between 270cm and 266cm net room height, that's nonsense. On your couch you will never notice that you are sitting 4 cm lower.



As for the planned screed thickness of 45 mm, it will not be a standard heating screed, as it is too thin.

The heating elements of a water underfloor heating system are usually 12 mm in diameter. If we add some uncertainties, we round up to 15 mm. The cement screed should match this thickness (15 mm) plus the enclosed thickness of 45 mm (60 mm total), which applies to conventional cement screed in residential construction.

If only 45mm was actually calculated and the thickness of the heating elements was subtracted, then 45mm – 12mm = 33mm would be left over the heating elements.

This is acceptable with mastic asphalt. So discuss this again with the general contractor. 

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