Ducting for hob in floor

[Rockomuir]

evening all,

Been to look at kitchen job today. All pretty straightforward except for self venting hob. The hob will be in an island about 1.5m from external wall. The floor plate is already down and there will be 50mm celotex and then 75mm screed on top. The ducting kit with the neff hob is 220mm x 90. Is pvc duct that they supply suitable to go under celotex and screed or does it have to be steel duct. I am worried that pvc duct will be damaged under weight of floor.

Any thoughts would be greatly appreciated

 

[ashrow]

Things to look at is what the finished floor covering is to.
I have install around 5 ducts like this with engineered wood flooring or tiled flooring and not had any call backs (but this was with 75mm to 100mm thermal insulation board and 50mm screed)

 

[Rockomuir]

The clients are thinking of wood flooring and even talk of a wet underfloor heating. Which is why ducting has to go under celotex and screed

 

[Octopus]

Is this a new extension?

 

[Rockomuir]

Yes

 

[Octopus]

Shouldn’t the celotex be 100 mm ?

 

[Rockomuir]

Yes it should, I have probably just got it wrong