Laying of pipes for electrical cables on the raw floor (screed with underfloor heating)

Hello everyone,

I am currently renovating my house (built in 1983) and installing a new underfloor heating system and screed.
The heating company laid two pipes for two existing radiators (for rooms where underfloor heating is not possible, see picture below). I would do the same for pipes for electrical cables on each floor (instead of laying them along the wall).



I believe there is a standard for pipe installation that requires a distance of 20 cm from the wall. But my screed installer said it would be better not to lay any pipes at all, but if so, then as close to the edge as possible. I am quite confused.

I want to discuss this topic here with experts and understand what is possible and what is not, based on the layout of the new screed.

Some information about the screed and the installation height:
The total available installation height (from the raw floor to the upper screed level where the tiles will be laid) is approximately 9.5 cm.

Ground floor

[*]PE foil 0.2 mm (200 my) as a moisture barrier on raw concrete ceilings, laid 1-layer with overlap
[*]PUR-Alu - (WLG 024) - 40 mm thick - thermal insulation boards made of polyurethane foam DIN 18 164 T1/B2, gas diffusion-tight laminated on both sides with aluminum foil.
[*]Grid foil
[*]Calcium sulfate flowing screed 50 mm nominal thickness CA-C25-F5 pH≥7 (EN 13813) according to DIN 18 560, laid floating on underfloor heating.

Upper floor/attic

[*]STYROFOAM - PS 20 SE - 20 mm thick - thermal insulation boards (WLG 040) made of polystyrene DIN 18 164 T1/B1, delivered and installed in bond.
[*]SYSTEM BOARD 25/20 mm for underfloor heating, made of polystyrene-PS-TK / SE-, d = 25/20 mm, impact sound and thermal insulation boards (WLG 045), stiffness group: 20 MN/m³; according to DIN 16 164 part 2, fire protection class: B1, with factory-laminated grid covering foil, for traffic loads up to 3.5 kN/m², delivered and installed including required edge strips;
[*]Calcium sulfate flowing screed 50 mm nominal thickness CA-C25-F5 pH≥7 (EN 13813) according to DIN 18 560, laid floating on underfloor heating.

In my case, it does not exactly comply with the standard because the pipes are not underneath the insulation board.

Instead

[IMG width="390px"]https://www.sanier.de/wp-content/uploads/images/estrich-rohrleitungen-ausgleichsschicht-grafik-nk.jpg[/IMG]
it would be like this...



My questions:

[*]Can I lay the pipes as planned directly on the raw floor? Do you recommend this or do you see risks (thermal bridges etc.)?
[*]Do I have to maintain a 20 cm distance from the wall or can I simply lay them exactly along the edges?
[*]How does the insulation board fit with this pipe? Since pipe and insulation board are on the same level, the pipe cuts through the insulation board. And the underfloor heating pipes are laid on top of that anyway, right?
[*]What is the maximum allowable pipe diameter (I assume it should not exceed the thickness of the insulation board, i.e. 40 mm for the ground floor and 20 mm for upper floors/attic)?

Thank you very much

Nym as well as underground cables can/may be laid simply along the wall at the bottom without a protective conduit.

Nym as well as underground cables can/may be laid along the wall at the bottom without protective conduit.

Thank you for the suggestion, but I definitely want to have conduits installed in case I want to change/replace the cables in the future.

Thank you for the suggestion, but I definitely want to have pipes installed in case I want to change/replace the cables in the future.

Sorry, but it is a misconception that you will change cables. I have not seen that in 30 years in the real estate industry (and with everyone I know). But there are no arguments against an "I want". ;-)

Sorry, but it is a misconception that you replace cables. I haven't seen that in 30 years in the real estate business (and with everyone I know). But there are no arguments against an "I want" ;-)

For me, it is mainly about flexibility in case I want to lay new cables, etc. I originally come from Italy, where that is the standard, and in 2005 I renovated my parents' apartment from the 70s (the original electrical installation had massive conductors XD... if the cables were laid directly in the wall, it would be quite a mess). Maybe I am also a bit biased. The house I bought (built in 1983) originally had cables laid in the walls, which for some reason were already laid in pipes in the floor.

Maybe I am also a bit biased there.

Yep, that's how it is. I can't think of a reason why anyone would want to replace an electrical cable. Even in 50 years, the electricity will flow just like it does today. You can also "just" replace a cable with a new cable (although the lifespan will probably be around 100 years). You won't bypass the changes to the installation this way – light switches elsewhere, lamps elsewhere, etc. Many cables you won't even be able to replace because they can't make all the bends due to their bending radii. In this respect, I would only lay NYM on the floor.