Thatched wiring - ways to make safer

[Mick-J]

Well....wiring in a 1750s thatched cottage attic, not wiring made from thatch
One we have been letting for over 20 years (as well as enjoying ourselves!)
I have read Thatch Roof Wiring - https://www.electriciansforums.net/threads/thatch-roof-wiring.106532, but welcome any ideas for us.

We occasionally have mice in our attic space (as any thatch will). Ideally we would like a thatch roofspace with no wires. But we have some. Regular cables to lights.
Our electrical certificate needed refreshing this summer, and the electrician we got was pretty thorough (although admitted to being unfamiliar with any special requirements regarding thatched properties).

He did, however, flag up some concerns over the "insulation resistance" of the upstairs lighting circuit.
The value seen on the circuit was 2.5MΩ. Apparently below 1 is a direct 'fail'
As comparison, the downstairs lights were 55....the cooker 500, the hob (directly behind the consumer unit) '>999'
He wasn't happy enough to give a 5-year certificate, so we only have 12 months, with the goal of 'remedying' things soon

The previous certificate was done after they had done some chunky work moving the main consumer unit from a hard to access space under the hob to go outside in the meter box....& all circuits are listed on that document as >200, which makes me suspect they didn't 'properly' test things That, or something has degraded massively & is at the point of failure

The house has two bedrooms upstairs, plus a 'new extension' bathroom off one: all with ceiling (& wall) lighting. Also a cupboard with lighting and a wall light over the stairs.

I am not a sparks, but we are considering solutions to this - ultimately, we want the place to be as safe as possible....albeit ideally without thousands of pounds of work We already removed the woodburner for a quality electrical replacement for safety reasons.

He has a couple of ideas which we will examine more later this week.

First one: to run SWA cable up into the attic, to replace all existing 'regular' plastic power cables.
SWA into some kind of ceiling 'light boxes' in the rooms below, where their can be junctions (none allowed now in the attic).
Using some 'kinetic' switches in the rooms to be able to power the lights without any physical connection. I've not found any that connect to 240v lighting, only some that connect to 12v under cupboard-style lighting. If anyone has pointers for those, I'd love to hear!
Sounds like we would need a fairly chunky box for the cabling to be done in the rooms below, & their ceilings are not that high....

Second one: to examine options for conduit. This might sound the simplest, but I believe might still require perhaps significant rewiring in order to get cabling into it - unless anyone can suggest conduit that can be wrapped around existing cabling? (which I feel would be a brilliant solution!)
He appears less keen on this....ultimately, our attic is relatively small, & perhaps the first option 'sounds' the easier & safer?


Has anyone here undertaken either of these....or indeed undertaken work to remove perhaps all wiring from the attic space below the thatch?
We cannot put wiring under the flooboards, because the rooms below are under the floorboards.....the joys of an old cottage.

Someone else mentioned Pyro/MICC....but they sound very specialised (from what I am reading!).

I'm also toying with how we could remove all attic wires - perhaps running wall lights from sockets, but the bathroom and staircase lighting might be harder (no sockets)
Another might be to monitor that resistance value to see if it has actually always been around 2.5 - I have no real idea how bad that is, or if it might be fine for the next 50 years....I suspect that the RCDs should trip IF a mouse were to nibble through, & given the cables are on the floor of the roofspace, away from thatch, that the risk of incident is fairly low.

Any hints, tips, dos/don'ts, etc, gratefully received.
& obviously we will be guided (driven?!) by the electrician: just fishing for ideas and experience other have.

 

[littlespark]

Very good thought processes here, concerning fire safety and rodent damage.

Removing electrical joints from within the attic space reduces the chances that a loose connection causing arcing could ignite the thatch.

SWA would certainly stop the little blighters getting to the wires, but once the outer sheath is nibbled away, the steel strands of the armour then become susceptible to moisture and can rust through.
Maybe not so quickly in an attic as it would, say, underground.

Pyro is a brand name of MICC (mineral insulated copper cable…. Or something like that) and is indeed almost bulletproof. Fire retardant, tooth proof and, as you say, specialist and very expensive.

Try searching for “quinetic” instead of kenetic. Again, it’s a brand name, but some on her swear by them as a solution to difficult cable routes.
Stair lighting is possible, as you can just pair two switches to the one controller.



Ever thought of replacing the thatch with corrugated iron sheets?

 

[pc1966]

Another couple of thoughts for attic wiring is to consider using Flexishild cable, it has a fairly tough outer sheath but otherwise is not too difficult to work with and one of the guys I know who does a lot of farm work recommends it to help deal with rodents.

Another thing you might want to consider for a high fire risk area is to have the circuit protected by an AFDD (arc fault detection device) which are now being mandated for certain classes of building, though more for socket circuits. They cost around £50-100 more than an RCBO but price is gradually falling.

MICC/pyro is indeed a solution that would last - probably a couple of centuries if unmolested! However, it is expensive and few folks now use it as for its most common use-case (fire alarm circuits where fire survival is needed) then the FP200 style of cable is cheaper and far easier to install.

Another traditional and totally rodent-proof solution is metal conduit. That then has PVC wires, etc, pulled through. These days it is normally seen only in industrial situations where mechanical strength / impact resistance is important, or occasionally if someone is wanting them seen for a steam-punk sort of look. It needs some skill to install, and I doubt that some "domestic installer" electricians would do that, but your more traditional spark would certainly have learned how to do so even if they rarely do it now. The "conlok" style of fittings are similar to those commonly used in the USA for light duty work and make installation much simpler and faster (no threading of ends, etc) and would be fine for a situation such as attic cabling.

Just to add - SWA is tough like conduit, etc, but terminating the ends usually needs a bit of work (glanding to suitable boxes, etc) and is not that suited to accessories like lights. However conduit has end-boxes available that are intended for things like pendant lights and so on to be attached so might work out easier to use overall.

 

[pc1966]

Just to add that FP200 is similar to Flexishield, though they have different intended use-cases. Both have a foil outer and bare earth drain-wire and that would help ensure that if damaged or nibbled then the RCBO should trip on the earth-fault even if current low.

The 2.5M resistance is suspiciously low: either damaged or poor cable, or damp & dust in some junction box or accessory.

 

[pc1966]

Here is a link to a PDF with some guidance, as the older forum thread's link is now broken:

https://nsmtltd.co.uk/wp-content/uploads/2019/01/2.-Electrical-Installations-in-Thatch-Pamphlet.pdf

 

[davesparks]

First thing I'd do is find the cause of the 2.5megohm reading if you are concerned about it.

Planning a rewire to cure something that could be caused by one aged light fitting seems a little extreme.

Whilst 2.5megohms sounds low don't forget that is still 2.5 million ohms which, if it is purely resistive, will give 0.0001 amps of leakage current at the upper supply limit of 253Volts

Personally I would only trust steel conduit or MICC to be rodent proof.

 

[snowhead]

Also before you go deciding on a plan and spending thousands on it, check with your building insurer to see if they have a prefered installation method, or guidance or want photgraphic evidence.
You may even get a reduced policy cost.

 

[Mick-J]

First thing I'd do is find the cause of the 2.5megohm reading if you are concerned about it.

Planning a rewire to cure something that could be caused by one aged light fitting seems a little extreme.

Whilst 2.5megohms sounds low don't forget that is still 2.5 million ohms which, if it is purely resistive, will give 0.0001 amps of leakage current at the upper supply limit of 253Volts

Personally I would only trust steel conduit or MICC to be rodent proof.

Thanks for all the replies, much appreciated

Good point about asking the insurer. That said, they were the reason we removed the log burner. One year they told us to put a steel liner in the chimney - okay, a grand spent….then the very next year they told us it needed insulating from the chimney. We gave up on that
We also read that over 97% of thatch fires started from the wood burner….so removing that should minimise one risk.

@davesparks:
Must admit I am unwise as to the impact of such a low reading….& of course whether it has been that low for 20+ years!
Also not sure how we would check light fittings to find if they are causing the issue.
As an unqualified but reasonably competent person, are there any suggestions (or devices I can use) to check fittings, or indeed the resistance?
Please note - I am not suggesting I take on the role of an electrician - he used a chunky looking box to test things - just aware I can check things whereas he would ideally want to come in, do whatever is needed, then move on!

It is an old cottage, although the extension which includes the upstairs bathroom was put on around 25years ago.

Interesting to hear about the AFDD. I will check whether that can be added to our CU, which is only 10 years old.

If so: would a good lower cost approach at this stage perhaps be to
1. Deploy an AFDD
2. Pop a wireless smoke alarm (we have a bunch interlinked ones) in the roof space for warning purposes)
3. Monitor the resistance reading to see how that goes over the next 12months
4. Have a crawl around the attic: check (& document) how the cables run in prep for any future changes. Ensure they are over 300mm from any thatch, perhaps.
5. Check light fittings

I imagine that might just be deferring the major work, but given we have no reference point to know if it has always been low, I wonder if that would make sense?

 

[Dustydazzler]

Roll out the Flexi-Con

Flexicon 25mm Galvanised Flexible Steel Conduit - 10Mtr | Flexicon (FU25-10M)

 

[Mick-J]

Roll out the Flexi-Con

Flexicon 25mm Galvanised Flexible Steel Conduit - 10Mtr | Flexicon (FU25-10M)

Interesting….although would require rewiring (can’t slip it over existing cable).
I was rather hoping there might be a steel conduit that existing cables could be tucked into

Any thoughts on my idea of following steps 1-5?
Cheers