Extend existing 40A unused circuit to shed

Discussion in 'Electricians' Talk' started by dtexh, Oct 22, 2021.

  1. dtexh

    dtexh Member

    I am a competent DIYer and experienced house renovator with experience doing electrical work and the equipment and self-taught competence to test the work I do.

    I have stuck a building control application form in, but haven't paid the fee yet and am having second thoughts as to whether it is technically notifiable. I do everything by the book, so want to do it properly, and if I have to pay the £350 I will, but it would be nice to save some money.

    Approved document Part P (England) is vague and I can't find detailed guidance on any of the scheme websites.
    • 40A unused RCD protected MCB & 6mm2 T&E, all in good nick, fitted in 2018 but power shower it was supplying was disconnected.
    • Plan is to terminate into a Wiska box, gland to 6mm2 SWA, run 6 metres into shed, terminate into a 45A cooker style switch, 3A fused spur for lights, 13A fused spur for underfloor heating mats to save wall space (mats draw a total of 7A), and a run of 9 sockets.
    Dwelling side is a TNS so exporting earth should be fine pending test results, no extraneous conductive parts in shed.
  2. Tony Goddard

    Tony Goddard Screwfix Select

    Re-using the circuit for another purpose is fine, what I'm not clear on is why you want to use a cooker switch and some spurs, that is a rather messy way of doing it, far better to use a 2 way CU with a 16A for sockets and a 6A for lights


    Take the 6mm direct into a 13A spur, then run your sockets in 2.5mm with a spur in there fused at 3A for your light, bit amateur but would work.

    In terms of notification, its easy to argue the method using the CU is creating extra circuits, but the second method certainly avoids that.

    You still need to issue a minor works certificate(s) for the job and perform the tests, presuming here you have access to a test set - the £350 you would spend on the LABC fee would I suggest cover the cost (or get very close) of the work being done by a pro, especially if you did the donkey work digging the trench for the SWA etc.

    in England notifiable works are:-

    Those in a special location (as defined, primarily bathrooms)
    The changing of a CU
    The provision of a new circuit

    This gives quite a lot of scope for DIY, but regardless the work needs to conform to the regs and Part P and the relevant tests made and certified via a certificate in the model forms section of the regs - for non notifiable circumstances this will be an MWC as an EIC by its nature involves the provision of a new circuit, an MWC covers an addition or alteration, the only circumstance I can think of an MWC being notifiable in England is in a bathroom.
  3. MGW

    MGW Screwfix Select

    As you say not easy reading with Part P to see if notifiable or not, need to define "new circuit" I would say not "new" so not required, in Wales fee £100 plus vat for first £2000 worth, in England varies council to council, £2000 is a rather high start point and the new rules allowed them to charge less, however it also allowed them to charge for a third party to inspect it.

    I was lucky in Wales as work was for the disabled so charges waved, however had problems getting the LABC inspector to accept my qualifications and an electrical installation certificate signed by me. Both my son and I had C&G 2391 but the inspector would not accept that, he did accept my degree in electrical and electronic engineering.

    The result was when it came to full re-wire of mothers house I decided to use a scheme member as cheaper, OK time was an issue with £600 a week care home charges for mother while being done, but it is so easy to end up costing more to DIY.
  4. dtexh

    dtexh Member

    Thanks for your replies. Yes, the reason for cooker switch idea was because it was a possible way around Part P, but on second thoughts yes it's probably best to do the job properly with a CU and cough up the £350. It covers them sending out an electrician to sign off my work.

    The reason I decided to go down the notification route was that electrician demand is high in the South East, so they are all quoting for months down the line, ghosting me once they'd been round, or wanting amounts like £2200. I don't blame them for capitalising on the demand, but it was too much for me personally.

    If I do go council route I think what I will do is put a 5 way Wylex CU (with a main switch not RCD) in the shed with 20A, 10A and 6A MCBs for sockets, underfloor heating and lighting, respectively. As house is on a TNS system will export the earth from the dwelling.
    Last edited: Oct 22, 2021
  5. The Happy Builder

    The Happy Builder Screwfix Select

    A cooker switch and switched fused connection units rather than fitting a garage consumer unit.

    Honestly, I don’t know what to say, you’ve got me :confused:
  6. Jimbo

    Jimbo Screwfix Select

    otoh if the 'consumer unit' for the shed didn't have a main switch, would it even be a consumer unit? just saying...
  7. The Happy Builder

    The Happy Builder Screwfix Select

    How is an electrical certificate going to be issued for Building Control without an electrician?
  8. Bazza-spark

    Bazza-spark Screwfix Select

    Very slowly and carefully, read #1.

    He has the equipment and knowledge (alledgedly).
  9. bright_Spark

    bright_Spark Screwfix Select

    Have you got any other installation certificates with your house for any other work that has been done? Do you have an up to date EICR on the house at the moment?
  10. Jimbo

    Jimbo Screwfix Select

    Probably 99% of homes in the UK don’t have an up to date EICR TBF
  11. The Happy Builder

    The Happy Builder Screwfix Select

    So is the plan is that @dtexh will write out an electrical certificate that will be accepted by Building Control or to use an electrician registered as a Third Party Certifier?

    Those may not be the best of plans.

    Probably better to use the £350 to pay an electrician in the first place.
  12. Bazza-spark

    Bazza-spark Screwfix Select

    Ask him, not me. I guess from #1 yes, he expects BC to accept his paperwork.
  13. bright_Spark

    bright_Spark Screwfix Select

    My point exactly Jimbo. I would say the same for sheds, the average house owner would not bother to notify a shed especially if there are no other certs on the house.
  14. The Happy Builder

    The Happy Builder Screwfix Select

    £350 to Building Control and still have to get an electrician to test and certify it.

    Good plan.
    Bazza likes this.
  15. Tony Goddard

    Tony Goddard Screwfix Select

    To be honest OP, if this is your own house and not being sold or rented, at the risk of incoming flak, I would just do it, do it properly with the CU and enjoy using it. As and when you come to sell or rent out you could have an EICR done or rip it out/disconnect prior to going on the market.

    Clearly over £2000 is bonkers for a shed, and the money is racking up the other way too.
    michael862 and bright_Spark like this.
  16. bright_Spark

    bright_Spark Screwfix Select

    Exactly this!!!
  17. dtexh

    dtexh Member

    No, LABC have confirmed that they will send an electrician to inspect and test my work, even though I will be testing it myself for my own learning/development. It costs extra for the electrician. If I were to fill out the certificate myself the fee would be £240 but they charge a bit extra to send out their appointed electrician.

    I don't know why some people on here are jumping to conclusions. I am very exacting, I don't want to roll the dice and end up with a cowboy job (have been bitten before and been left with crappy workmanship and a fight when I could have saved the hassle and done it myself) so I prefer to do the work on my own house myself so I get it perfect. Ultimately the good electricians are harmed by the fact people are put off by all the cowboys out there.
    Last edited: Oct 23, 2021
  18. dtexh

    dtexh Member

    Consumer unit changed and self certified by a NICEIC certified electrician couple of years ago.
  19. bright_Spark

    bright_Spark Screwfix Select

    So the shower supply will be on the cert for the CU?
  20. dtexh

    dtexh Member


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