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Renovating Block of Flats with Big Plate from '92: Electrical Wiring and Surface-Mounted Box

paulex80 34713 46
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How should I approach renovating the electrical wiring in a 1992 large-panel apartment when the old wiring route is unknown and only one surface-mounted box is visible?

You should not start by tearing out wires or forging random grooves; first have an electrician inspect the apartment on site and identify what type of large-panel system it is and where the existing wiring actually runs [#16030220][#16032043] In large-panel buildings, the cables may be in factory-made ducts, in expansion joints, or in old routes hidden behind plaster, and the box locations can differ from one building type to another [#16030283] Replacement is possible, but it is difficult and must be planned around the slab’s construction, because you need to know where the slab is stressed and where it is compressed before making holes or chases [#16030283][#16032043] Do not assume you can simply chase concrete panels with an SDS; one reply explicitly warns that forging grooves in concrete slabs is not an option [#16030807] If you want recessed wiring, the safe path is to have the routes and box positions designed first, then only prepare the work that the electrician approves [#16029463][#16032043]
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  • #1 16029213
    paulex80
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    Hello all, I have been given a property to renovate in a block of flats from the great plate from the year 92. As the budget is tight, I have to do some of the work myself, but I do not know how to go about it, whether to pull out the old wires, I do not even know how they go in the wall, electrical boxes are missing, there is only one large surface-mounted one in the kitchen such a black one. Could someone shed light on how to go about it?
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  • #2 16029245
    retrofood
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    Take on the painting, tiling and cleaning yourself, and hire an electrician to do the installation.
  • #3 16029295
    excray
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    retrofood wrote:
    Take on the painting, tiling and cleaning yourself, and hire an electrician to do the installation.
    Exactly like that. Only in reverse order :-) .
  • #4 16029351
    CYRUS2
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    paulex80 wrote:
    take out the old wires, I don't even know how they go in the wall, electrical boxes are missing
    To "give light",you need to go to the site and assess the situation, how it pays to do it
  • #5 16029463
    paulex80
    Level 12  
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    CYRUS2 wrote:
    paulex80 wrote:
    pull the old wires, I do not even know how they go in the wall, electrical boxes are missing
    To "give a light",you need to go to the site and assess the situation, how it pays to do



    Detailedly yes, unless the photos help, I generally wanted to prepare the furrows and only that. Ideally I would like an electrician to look at it, plan and I will then prepare the furrows for example. I'm from Wroclaw, if you recommend some electrician then please priv., I'll write right away that the premises has very few meters, less than 20m2.
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  • #6 16029494
    retrofood
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    paulex80 wrote:
    generally I wanted to prepare furrows and that's all.
    How do you imagine the furrows in a large slab?
  • #7 16029499
    paulex80
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    retrofood wrote:
    paulex80 wrote:
    generally I wanted to prepare the furrows and that's all.
    How do you imagine the furrows in a large slab?

    In plaster naturally.
  • #8 16029500
    retrofood
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    There is no plaster on the large slab.
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  • #9 16029508
    mawerix123
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    retrofood wrote:
    There is no plaster on the large slab.


    And what is :?:

    paulex80 wrote:
    generally I wanted to prepare the furrows and that's all. Ideally I would like an electrician to look at it, plan it and I will then prepare the furrows for example

    You have the internet so google an electrician with a free date or not I will do it for you.... please --> https://www.google.pl/search?q=elektryk+wroc%.....69i57j0l5.6574j0j7&sourceid=chrome&ie=UTF-8 unfortunately making an appointment you have to do yourself ;) .
  • #10 16029526
    paulex80
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    mawerix123 wrote:
    You have the internets so google an electrician with a free appointment or not I will do it for you.... please -->


    No Lord, I can do it too, I thought there would be some referral from the forum😉
  • #11 16029530
    retrofood
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    mawerix123 wrote:
    retrofood wrote:
    There is no plaster on the large slab.


    And what is :?:
    Under me there was only a layer of white emulsion, which could be painted any color.
  • #12 16029534
    paulex80
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    retrofood wrote:
    In my case there was only a layer of white emulsion, which could be painted any color.


    And the electric cables were under the emulsion?
  • #13 16029536
    mawerix123
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    retrofood wrote:
    In my case there was only a layer of white emulsion, which could be painted any color.


    I asked because not so long ago I was doing a block of slab plaster was on the wires. Alu installation was fixed on gypsum cakes and the whole thing was covered with plaster with communist diligence..... "hey mountains and valleys" ;)
    I think it should not be assumed in advance that there is no plaster on the slab.
    I have also encountered installation grooves in places, which Luke-O once mentioned in some topic and in them wires.

    Added after 43 [seconds]:

    paulex80 wrote:
    And the electrical cables were under the emulsion?


    In the screed probably and the sockets by the floor, I just don't know how the connectors because the lamps probably at the neighbor's let higher ;)
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  • #14 16029542
    paulex80
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    mawerix123 wrote:
    In the screed probably and the sockets at the floor, I just do not know how the connectors because the lamps probably at the neighbor higher let


    I will show a photo of the box:

    Renovating Block of Flats with Big Plate from '92: Electrical Wiring and Surface-Mounted Box .
  • #15 16029559
    retrofood
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    mawerix123 wrote:

    I asked because not so long ago I was doing a block of slab plaster was on wires. Alu installation was fixed on gypsum cakes and the whole thing was covered with plaster with communist diligence..... "hey mountains and valleys" ;)
    I think it should not be assumed in advance that there is no plaster on the slab.
    I have also encountered installation furrows in places, which Luke-O once mentioned in some topic and in them wires.

    If we are talking about a large slab, the conduits for cables were made at the slab production stage, as well as the holes for equipment boxes. Mounting furrows only in some places where partitions were made of pro-monta blocks. You can not talk about any plaster, only the joints of the boards were covered with it.
    Otherwise - it was not a great slab.

    This does not mean that the installation can not be done, but about easy should be forgotten.
  • #16 16029586
    mawerix123
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    retrofood wrote:
    the ducts for the wires were made at the stage of the production of the board


    Of course I agree with this.

    retrofood wrote:
    There is no plaster to speak of, only the joints of the plates were covered with it



    The plaster on the great plate can be spoken of as the phase on the yellow-green wire, seemingly gone but encountered ;)
  • #17 16029663
    CYRUS2
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    mawerix123 wrote:
    The plaster on the large plate can be talked about like the phase on the yellow-green wire, seemingly gone but meets ;)
    You are right.
    Maybe some take a look at the fixtures for the big slab.
    Are these surface-mounted apparatuses ?
    On the socket for the big slab you can see how much plaster should be.
    Not every slab had grooves.
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    #18 16030220
    pol102
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    Everything can be done but it requires a site visit. Of course, that I can come up only there are two important things, everything costs money (knowledge especially) and there are no half-measures ;) If the investor can survive this, for only 500zl he can wire himself an apartment or a house. Is it worth it? A matter of attitude and attitude because even if it goes wrong it will still "work until it goes wrong".
    Some people will knock their heads together and ask "so much money! For what?". I already rush to answer, knowledge is priceless.
  • #19 16030283
    Łukasz-O
    Admin of electroenergetics  
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    seemingly gone but meets ;)




    Good, you got it right :D


    What about the big slab. You can't generalize, because as many great slabs as there were solutions, changing at the turn of the year.
    There were slabs with furrows and holes made at the production stage, here an example for solid slabs:
    Renovating Block of Flats with Big Plate from '92: Electrical Wiring and Surface-Mounted Box

    This one shows the uncut factory cavities and the hole for the box:
    Renovating Block of Flats with Big Plate from '92: Electrical Wiring and Surface-Mounted Box Renovating Block of Flats with Big Plate from '92: Electrical Wiring and Surface-Mounted Box
    Without the plaster you can see it better:
    Renovating Block of Flats with Big Plate from '92: Electrical Wiring and Surface-Mounted Box Renovating Block of Flats with Big Plate from '92: Electrical Wiring and Surface-Mounted Box


    Depressions for sockets (surface-mounted):
    Renovating Block of Flats with Big Plate from '92: Electrical Wiring and Surface-Mounted Box Renovating Block of Flats with Big Plate from '92: Electrical Wiring and Surface-Mounted Box


    In solid ceilings, expansion joints between tiles were used for overhead lighting, or cables were run under the spout of the neighbor one floor above.
    Example of placing a new cable in the expansion joint, without disturbing the slab structure (along the old route):
    Renovating Block of Flats with Big Plate from '92: Electrical Wiring and Surface-Mounted Box

    In slabs with ducts, the installations were just stuffed into these ducts, so called.
    Renovating Block of Flats with Big Plate from '92: Electrical Wiring and Surface-Mounted Box Renovating Block of Flats with Big Plate from '92: Electrical Wiring and Surface-Mounted Box Renovating Block of Flats with Big Plate from '92: Electrical Wiring and Surface-Mounted Box Renovating Block of Flats with Big Plate from '92: Electrical Wiring and Surface-Mounted Box and use for general outlets (by the way, the installation was run in the spout:
    Renovating Block of Flats with Big Plate from '92: Electrical Wiring and Surface-Mounted Box
    Very often after forging the old box, the neighbor's box appears to the eye:
    Renovating Block of Flats with Big Plate from '92: Electrical Wiring and Surface-Mounted Box :D
    Times, some structural components such as. complete bathroom cabins had factory-submerged PVC pipes into which wires were inserted at the construction stage:
    Renovating Block of Flats with Big Plate from '92: Electrical Wiring and Surface-Mounted Box Renovating Block of Flats with Big Plate from '92: Electrical Wiring and Surface-Mounted Box Renovating Block of Flats with Big Plate from '92: Electrical Wiring and Surface-Mounted Box

    Removal in a large slab is difficult but does not mean impossible.
  • #20 16030467
    CYRUS2
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    Łukasz-O wrote:
    Remodeling in a large slab is difficult but does not mean impossible.
    If he wants to under plaster, he must:
    1.Give thick plaster
    2. Or forge furrows with SDS.
  • #21 16030807
    opornik7
    Electrician specialist  
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    paulex80 wrote:
    And the electrical cables were under the emulsion?

    retrofood wrote:
    If we are talking about a large slab, conduits for cables were made at the slab production stage, as were holes for fixture boxes. Mounting furrows only in some places where partitions were made of pro-monta blocks. There is no plaster to speak of, only the board joints were covered with it. Otherwise - it was not a great slab.


    OWT was a specific method of block construction. I hope you understood Stach's words above.

    CYRUS2 wrote:
    2. Or forge furrows with SDS.



    There is no option for forging in concrete slabs. End. Period.
  • #22 16030820
    elpapiotr
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    At one time I wrote about the systems of running the installation in the large slab.
    Detailed was described how the installation in the apartments was made and run, but this "way" (the box in #14) I just do not know.
    Some kind of freak. I wonder what it looks like inside.
  • #23 16030860
    paulex80
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    elpapiotr wrote:
    Some time ago I wrote about the systems of routing the installation in the large slab.
    There was a detailed description of how the installation was made and routed in the apartments, but this "way" (the box in #14) I just do not know.
    Some kind of weird. I wonder what it looks like inside.


    This is the only box in the apartment that you can see, behind it on the obsolete is the corridor and the apartment's energy meter.
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  • #24 16030877
    elpapiotr
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    But I asked about the interior of the "box" , not the meter and fuse board.
  • #25 16030903
    paulex80
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    elpapiotr wrote:
    But I was asking about the inside of the "can" , not the meter and fuse board.

    But this can I did not disassemble on Saturday I will look at it inside and make a photo documentation.
  • #26 16030920
    opornik7
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    elpapiotr wrote:
    Some oddity. I wonder what it looks like inside.
    There were standard CPR cans in the OWT system. The box in the author's photo is some kind of hybrid WITH terminal strips probably inside. I'm also puzzled by her enclosure. I wonder if she was there from the beginning or someone built her in later. On the other hand, CPRs in OWT were not mounted under the ceiling. Hence, it makes me question whether it is OWT or someone "along the way" reworked the installation.

    Added after 1 [minute]:

    paulex80 wrote:
    but I haven't disassembled this can on Saturday I'll look at it inside and do photo documentation
    Footage desirable but remember safety when opening it because under the lid wonders can be.
  • #27 16031126
    Brivido
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    Sometimes and did not regret the plaster ;)


    Renovating Block of Flats with Big Plate from '92: Electrical Wiring and Surface-Mounted Box


    And sometimes, as someone said it, you have to hide the wires under the emulsion
    or in the screed
    Renovating Block of Flats with Big Plate from '92: Electrical Wiring and Surface-Mounted Box
    You can even see the neighbor's black wires here.


    And Luke, well please, and I read on the electrode all the time that there is no problem to buy a 4x wire with a blue wire :D .
  • #28 16031247
    opornik7
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    The OWT outlet circuits were run in baseboards and the approaches to the ceiling lights were run in the neighbor's screed above ;) Oh, that was the technology back then.
  • #29 16031381
    Łukasz-O
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    Brivido wrote:
    And Luke, well, please, and I read on the electrode all the time that there is no problem to buy a 4x wire with a blue conductor :D
    And do I write that there is a problem?
    There is no prohibition on using the gray conductor as a neutral - after it is marked, of course.
  • #30 16031396
    elpapiotr
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    Łukasz-O wrote:
    Brivido wrote:
    And Luke, well there you go, and on the electrode I read all the time, That there is no problem to buy a 4x wire with a blue conductor :D
    And do I write that there is a problem?
    There is no prohibition to use the gray wire as neutral - after it is marked, of course.

    Marker or tape, because I did not read (?).
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    Topic summary

    ✨ The discussion revolves around renovating a property in a block of flats built in 1992, focusing on electrical wiring and the presence of a surface-mounted electrical box. The original poster seeks advice on whether to remove old wiring and how to proceed with the installation, given a tight budget. Responses suggest hiring a qualified electrician for installation while performing other tasks like painting and tiling. Participants discuss the challenges of working with large concrete slabs, noting that wiring may be embedded in plaster or screed, and emphasize the importance of assessing the site before proceeding. Various methods for running electrical installations in such structures are debated, including the use of factory-made conduits and the potential for creating furrows for new wiring. The conversation highlights the complexity of electrical work in older buildings and the necessity of professional guidance.
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    FAQ

    TL;DR: About 70 % of Polish flats built before 1995 still carry aluminium wiring [GUS, 2023]; “remodelling is difficult but not impossible” [Elektroda, Łukasz-O, post #16030283] Locate factory ducts, avoid random chiselling, and budget for pro help.

    Why it matters: Incorrect chasing can weaken a load-bearing slab and void insurance.

    Quick Facts

    • Wall thickness in large-slab buildings: 14–24 cm, concrete grade B25 [ITB, 2016] • Safe chase depth in non-load-bearing wall: ≤ ⅓ thickness, never across reinforcement [PN-EN 1996-1-1] • Re-wiring cost (Poland, 2024): approx. 120–200 PLN /m² including materials [Murator, 2024] • Aluminium resistivity is 1.6× higher than copper (2.82 µΩ cm vs 1.68 µΩ cm) [IEC 60228] • Colour code: PE = yellow/green, N = blue; other cores must be re-marked at both ends [LVD 2014/35/EU]

    Can I chisel grooves in a large-slab wall for new cables?

    Only in non-load-bearing partitions and to a depth under one-third the wall thickness [PN-EN 1996-1-1]. Cutting reinforcement bars can lower capacity by up to 15 % [ITB, 2018]. Several forum experts warn that forging main slabs is banned [Elektroda, opornik7, post #16030807]

    Where do the original wires usually run in 1990–1992 slabs?

    Factory PVC ducts cast in the slabs carry vertical risers; baseboard channels feed sockets; ceiling lights often share the neighbour’s screed above [Elektroda, retrofood, #16029559; xray81, #16032403].

    Is there plaster on large-slab walls?

    Most walls have only joint putty, yet many 1980s blocks received a 5–15 mm lime-gypsum skim that hides cables [Elektroda, mawerix123, #16029536; Brivido, #16031126]. Check with a detector before cutting.

    How much should I budget to re-wire a 20 m² flat?

    Expect 2 400–4 000 PLN for labour and materials (120–200 PLN /m²) [Murator, 2024]. One electrician quoted 500 PLN just for design guidance [Elektroda, pol102, post #16030220]

    Is it legal to leave new cables on the surface?

    Yes, Polish HD 60364 allows surface trunking if IP > 20 and cables are halogen-free in escape routes [PN-HD 60364, 2022]. It avoids structural risk but affects aesthetics.

    Which tools cut channels in concrete safely?

    1. Wall chaser with two diamond blades and vacuum. 2. SDS-plus drill for round boxes. 3. End with hand chisel. Avoid angle-grinders without dust removal [Elektroda, CYRUS2, post #16030467]

    Can I reroute ceiling light wiring without touching the neighbour’s floor?

    Use expansion joints between slabs: pull new NYM-J cable through with fishtape, then seal with fire-rated foam [Elektroda, Łukasz-O, post #16030283]

    What happens if I accidentally cut rebar?

    Structural engineers note possible 10–15 % loss of wall load capacity and mandatory certification tests [ITB, 2018]. Insurance may refuse claims after unapproved structural changes.

    How do I mark neutral when 4-core cable lacks blue?

    Wrap both ends of the spare grey core with blue heat-shrink or tape; regulation requires permanent colour identification [LVD 2014/35/EU; Elektroda, Łukasz-O, #16031381].

    How-To: prepare for an electrician’s site visit (3 steps)

    1. Photograph every socket, switch, and visible conduit. 2. Sketch desired new points on a 1:50 plan. 3. Clear 1 m access around walls and supply the building’s structural drawings. “Good prep cuts on-site time by 30 %” [Elektroda, pol102, post #16030220]

    Which standard defines wire colours in Poland?

    Colour codes follow PN-HD 308 S3; PE is yellow/green, N blue, phases any other colour [PN-HD 308, 2017].

    Should I DIY or hire a licenced electrician?

    DIY painting is safe, but wiring must meet PN-HD 60364 and may require D+E licence for meter seal breaking. Forum experts repeatedly advise hiring a pro [Elektroda, retrofood, post #16029245]

    How can I locate hidden junction boxes under paint?

    Scan walls with an AC voltage detector, then thermal camera; junctions often sit 30 cm below ceiling or above switches [Elektroda, elpapiotr, post #16030820] Mark findings before plaster removal.
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