Hmm, self-build self-wiring consideration

[PikeyDIY]

I have never done anything to do with electrics before, and had not previously considered doing any of the wiring myself, but speaking to someone recently it seems they think I could do most of the first fix wiring on our new timber frame house myself, with some advice.

Earlier in the build, I hadnt considered doing any of the block or bricklaying - but we made a perfectly decent job of that. Admittedly, brickwork is unlikely to catch fire or explode, but it's just an example of something I've done that I didnt previously think I could do

What would be your thoughts on this? Do some research and have a go? Or leave it to the pros?

Jeff

 

[rebuke]

If you've never done it before, I wouldn't suggest doing the first fix yourself would be a good idea (you need to know how to select cable sizes, protective devices and lots and lots of other things).

If you're looking to save money, I would suggest find an electrician you get on with, and see if you can do some of the donkey work for him, such as laying and clipping cables etc (normally i'd say chasing out walls, but I guess a timber frame house won't need that as such!) - this way he can provide you with the right type of cable to use, and instruct you where to route it (so he will still be happy to sign off on the work) but you're doing the grunt work to save him the time and effort (and yourself £s!).

 

[Taylortwocities]

Leave it to the pros, you'll never get building regs signed off otherwise and you'll never learn enough to make a success of it from the Internet.!

As a middle way, find yourself a friendly registered electrician and work with him - he can do the design second fix and testing you can run the cables under his guidance.

 

[Adam_151]

What did you put in your plans submission to the building control dept.? WRT to how you plan to meet part P of the building regulations (or what did your artitect put?)

If it was along the lines of using a contractor who can self certify, then you are ****ed unless they will letr you alter it, if it didn't say that then its upto building control to inspect your work in the same way that they inspect your brickwork and your windows.

On the practical side, I'd say go for it, wiring a new build is far from rocket science, dead easy to chuck standard circuits in, you'll want to get a good book, read it, read this forum, perhaps become mates with an electrician who can give hints and advice in the flesh, be nice to your buildings control guy and wear sunscreen

 

[ColJack]

it's a complete from the ground up bungalow build.. so does the sparky need to be registered?.. the LABC will be checking it all off anyway..

as it's timber frame, most circuits won't be standard sizes.. 32A rings would need to be 4mm² ( insulated walls and ceilings ).
lights can still be 1.5mm² ( grosly oversized anyway for a 6A lighting circuit )
shower might be a problem.. 45A circuit in 10mm² is ok in the wall but under 100mm+ of insulation in the ceiling would not be.. ( 36A, ref method 101 ).
hob circuit on 10mm² with a 32A breaker..
oven circuit on 4mm² with a 20A breaker..

 

[Adam_151]

Reference method #102 coljack, T+E between insulation and plasterboard in contact with plasterboard, 2.5mm is rated at 21A amps, 6mm at 35A and 10mm at 47A

You don't think all these barratt estates have 4mm rings do you?

 

[bernardgreen]

What would be your thoughts on this? Do some research and have a go? Or leave it to the pros?

Do the research, then do a good well documented design of the installation and then discuss it with the LABC as to whether they will accept your self certification based on their assesment of your ability to self certify work for your own home.

You may find they are more flexible than you think. And if they are not you have not lost anything other than a few hours time.

 

[ColJack]

as it's having a flat roof, there will be insulation in the roof.. and I recon it will be more than 100mm..
so running the cables in the ceiling would be ref method 101.. 2.5mm comes out at 17A.. not enough to satisfy reg 433.1.5 ( Iz >= 20A )
4mm comes out at 22A.. hence the suggestion..

 

[ColJack]

200mm deep walls? is that a typo on your self build blog page?

 

[PikeyDIY]

The ceiling is 300dp engineered timber joists, with a ply deck over, with rigid board insulation on top of the ply deck. So the roof is not a problem - basically a 300dp void above the plasterboard ceiling.

The walls are 200mmm thick, yes, full of recycled plastic insulation.

Building Control is NHBC, not Local Authority. I have a good relationship with the Building Inspector though, so I cant see that being a problem.

 

[Taylortwocities]

But surely you have to comply with all of the parts of Building Regulations that apply to your building?

That compliance is ultimately controlled by your LABC.

 

[ColJack]

ok, so then 2.5 rings will be ok..

wohoo.. no need to RCD all the wiring either!!!

bit confused over the NHBC vs LABC though.. ask the building inspector next time he comes about part P, see what he says..

 

[PikeyDIY]

We've paid all our fees to the NHBC, and all our correspondence is with them. I will ask our Inspector about the electrics next time he is on site

I've got a self-build book out of the library which goes into electrics, it is from a while ago though, but I'm learning a bit

 

[LiamPope]

There are a few DIYers on here (I'm one) doing, contemplating, or who've already done full installations themselves, but not many (most are scared away by BAS ). However, unlike laying bricks, etc, which you can jump straight into and improve on over time, the job of 'doing the electrics' starts with the design stage - a paper exercise for which considerable knowledge is required. So you've got much to read and learn of design, practical, and regulatory issues before you can even start to route your first cable - there's no such thing as jumping into the first fix and learning as you go.

You're obviously pretty capable if you're building the whole house, and if you're prepared to take on the academic learning excercise, you can do the electrcs too. That's providing you have the time to learn what you need to know before the wiring has to start (looks from your blog like you do ).

If you're going to learn enough to design the installation and start it, you'll know enough by then to do the whole lot, not just first fix! But if you really just want to do some donkey work to keep costs down without investing the time in the learning (you do have a whole house build to manage!), or you just haven't the time as the wiring has to start imminently, you are probably better off engaging an electrician right at the start, having him responsible for the design, and you doing the first fix leg work under his instruction.

Good luck anyway,

Liam

 

[Stoday]

Using the NHBC instead of LABC means you get a guarantee thrown into the fee. Just what I did with my self build finished in 2006. LABC was not involved and never made a visit.

NHBC inspector has a different motivation from LABC. He's there primarily to make sure they don't have to pay out on the guarantee, so the rules in the building regs have different priorities.