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

 

[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!

Assuming it is PVC insulated cable and not some extremely old rubber or paper insulated cable then 2.5megohm reading suggests something like a little bit of contamination at some connections, a slightly leaky LED driver, and old lampholder in its way out, flourescent ballast.
Or it could just be that a lamp was left in a fitting by accident when the test was carried out.

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?

You would need an insulation resistance tester, this applies a voltage of 500V and measures the resistance in megohms.

Any electrician will have one and be able to find the cause for you.

The process they will follow is quite simple, you estimate where the middle of the circuit is and break it there, test each half of the circuit to find which half has the issue.
Then you split that half circuit in half again and re-test, and just follow this process until you find the cause.

 

[pc1966]

First thing I would suggest is making sure you have some flooring in the attic so you don't easily fall through the roof! Almost came a cropper myself a few years back when foot missed a beam

Without the equipment to test at 500V, etc, probably the best you can do is inspect the cables for any sign of damage (mice, or crushed, etc) and look for junction boxes, etc, that could be filled with dust, etc. Take care as you might find a cable that is exposed in a spot you don't see and then touching it will be BAD news. Even if you don't get killed by the shock due to RCD/RCBO protection, jumping in response and falling through a roof is potentially as bad.

While you can get metal trunking that could be fitted around exiting cable, it is not going to be practical to cover enough of it and you still have the problem of keeping mice out of that, so ends have to be pretty well sealed to gaps of few mm and realistically that means cables removed at ends, and by the point starting fresh makes more sense. You are probably not considering a total rewire, and it might be the only circuit in the attic is the lights, but if sockets are fed down from above then it is more to consider. Usually the biggest time/cost and trouble is routing wires through walls (where chased in / plastered over) so if mostly that is not needed then it might not be too expensive.

The 2.5M is not on its own a problem, it is more it indicates something is wrong and that could become a problem. It might be something like the cable is nicked against a nail/screw in to wood and that is your 2.5M path to Earth, but it might also be due to mice removing PVC insulation, etc. So it could be very cheap to fix if just dirt in a poorly covered junction box all the way to cables needing replacement.

 

[Mick-J]

Thanks again for both of your helpful replies
Food for thought and indeed discussion when we see our sparky fella on Friday

 

[Risteard]

Roll out the Flexi-Con

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

You might need to remortgage the house to wire it in kopex.

 

[Mike Johnson]

As you say that the cables in the loft are "regular lighting" that would probably mean 1.0 or 1.5 T&E this existing cable could easily be pulled through 20mm Flexicon galvanised steel conduit, your electrician should know who its done and terminated into each light fitting.

 

[davesparks]

As you say that the cables in the loft are "regular lighting" that would probably mean 1.0 or 1.5 T&E this existing cable could easily be pulled through 20mm Flexicon galvanised steel conduit, your electrician should know who its done and terminated into each light fitting.

But to pull it through floppy conduit the whole lot would have to be disconnected and re-run so it might as well be rewired and made properly rodent proof.

Properly terminating the floppy conduit at light fittings and switches wont be all that straightforward either.

 

[Mike Johnson]

Only has to be disconnected one end and a draw cord pulled through then the existing T&E can easily be terminated in a standard stuffing gland, not rocket science although some on here think it is.

 

[nicebutdim]

Only has to be disconnected one end and a draw cord pulled through then the existing T&E can easily be terminated in a standard stuffing gland, not rocket science although some on here think it is.

I don't believe you've thought this through. Cables routed through walls/joists etc won't have been run to accommodate the significantly larger diameter required and will need to be pulled back to allow this work.

While steel flexible conduit is one means of protecting cables from rodents, in this instance I can't imagine fitting the stuff over existing cables being a worthwhile or economical endeavour.

 

[Mike Johnson]

I have thought this through, it is only lighting cables that are needing protection, these will be run from rose too rose so easily disconnected and pulled back and through a flexible conduit laid on and clipped too the surface of the joists, any cables that go through the ceiling can be terminated inside a box over the penetration.

So what is your better solution?

 

[Rockingit]

Personally, I'd have thought that the quickest/cheapest way to deal with this would be standard runs of galv tube, conduit outlet above where each light below is (can screw a 3 plate straight through the [wattle?] ceiling into it) and then use 2way 90's to jam down to trap the switch drops coming back up the wall. I'd have thought that they'd be fine, it'll be the loops that are nibbled through.

Or does nobody know how to use a bender anymore?

 

[Dustydazzler]

I would rewire it all in 4mm SWA , all metal tie wrapped to some nice Galv Tray strutted to the roof joists

 

[pc1966]

I would rewire it all in 4mm SWA , all metal tie wrapped to some nice Galv Tray strutted to the roof joists

Why 4mm?

SWA would work, but to me conduit and singles would be far easier for various loops or two-way switches, etc. Possibly less work even with the conlok style as you won't have a dozen or so cable glands to accessories and/or junction boxes in the roof space.

Any runs impractical to do in metal conduit could be in flexible, or maybe a run or SWA as needed (potentially 7 core, etc, for many circuits so long as off one breaker).

 

[Dustydazzler]

Why 4mm?

...cause I got a load of it in the shed that needs using up

 

[davesparks]

Only has to be disconnected one end and a draw cord pulled through then the existing T&E can easily be terminated in a standard stuffing gland, not rocket science although some on here think it is.

But how are you terminating the floppy conduit at each end, or are you proposing to just leave the sharp cut end of the steel loose? It needs to be connected onto a backbox of some sort with a proper gland to secure it and protect the cable from the sharp edges.

If the conduit is left loose and not secured to backboxes then it will inevitably leave a bit of cable exposed for the rodents to nibble on.

The floppy conduit is unlikely to be able to take the exact same route as the existing cables so will inevitably result in the cables being too short.

 

[davesparks]

I have thought this through, it is only lighting cables that are needing protection, these will be run from rose too rose so easily disconnected and pulled back and through a flexible conduit

I hadn't realised you've visited the house in question and know exactly how the circuit is wired and how the cables have been run.

 

[Mike Johnson]

Of course I haven't visited the house, but do live an equally old property, these are just ideas and suggestions, no else seems eager to have a punt on a solution, perhaps it's because they know that it will bring out the Harry Enfield effect in most others.

 

[davesparks]

no else seems eager to have a punt on a solution,

I've already made my suggestion of finding the cause of the 2.5megohm reading rather than rewiring and entire circuit for the sake of what could be a faulty lampholder.

 

[Mike Johnson]

That does not get over the Rodent problem, which is what this thread is about.

 

[Mick-J]

You're both right. & I appreciate the replies.

We could do with finding the cause of the low reading in the first instance.....which might give us some grace for a period before figuring out a med-long term solution.

To that end I do plan to gird my loins, pull on my worst clothing and have a careful creep around the attic.....just need a damp day and some enthusiasm for getting up the ladder The former should happen this week....

The longer term solution must involve removing/solving the rodent issue.
In my mind, that would ideally mean removing all wires from the attic....BUT given the bathroom has a pull-cord ceiling light, that might not be possible. Or involve plenty of in-room conduit perhaps

Our sparky is a busy fella (and we are not around a lot)...plus he is aware that once he does any work, he would need to take it all to current regs......so who fancies a trip to the IOW to cure the problem? Free holiday plus some payment


He did explain how to run tests using a Megger meter in order to perhaps monitor things ourselves a bit. Hopefully that will give us more information!
What we don't know is whether the low resistance is something that has been getting worse, or indeed if it has been bad for 5-20 years. Defo worth knowing that.....

cheers

 

[Avo Mk8]

A couple of other options?

https://www.techflex.co.uk/heavy-duty/rodent-resistant-sleeving

Anti-Rodent Electrical Tape - ATV City

Anti-Rodent Electrical Tape (20m) An easy to use, effective solution for protection of cables, wires, plumbing pipes, gas pipes & ducts against rodent damage! Teraokatape is embedded with capsules containing Capsicum which are extremely disliked by rats and mice. Simply wrap the tape around wire...

atvcity.co.uk

 

[pc1966]

A couple of other options?

The sleeving has all of the other issues of basically having to disconnect and reconnect cables, so not far off effort to rewire.

However, the tape might be an idea, no idea how much it would cost to cover all of the cables though - works out at around £1/m but not sure tape length in practice to cable covered, etc.

 

[Avo Mk8]

The sleeving has all of the other issues of basically having to disconnect and reconnect cables, so not far off effort to rewire.

However, the tape might be an idea, no idea how much it would cost to cover all of the cables though - works out at around £1/m but not sure tape length in practice to cable covered, etc.

The sleeving I was originally looking for was the 'self closing' type, but I drew a blank.

But I've just found the product below, which overcomes the dis/re-connect problem. I suspect it may not be quite as effective as I don't think it has a dissuasive chemical component.

Rodent repellent self-closing sleeving Twist-In-RR-13 (170-01161)

170-01161

www.hellermanntyton.com

 

[nicebutdim]

But I've just found the product below, which overcomes the dis/re-connect problem. I suspect it may not be quite as effective as I don't think it has a dissuasive chemical component.

Blurb states "optimal protection from rodents and martens". Has to be pretty tough as the latter can eat through almost anything.

 

[Rockingit]

Ermmm….. surely all this talk of wraps and covers is irrelevant when the IR readings are saying it all needs replacing anyway??

 

[nicebutdim]

Ermmm….. surely all this talk of wraps and covers is irrelevant when the IR readings are saying it all needs replacing anyway??

OP expressed concerns about rodents. Quite likely they wouldn't want new cables chewed, if it turns out the cables need to be replaced. For now we know there has been a poor IR reading, but we don't know for certain that cables are the issue.

 

[littlespark]

Blurb states "optimal protection from rodents and martens". Has to be pretty tough as the latter can eat through almost anything.

Why did I read “Martians” there?

As if rodents weren’t enough….

 

[pc1966]

Blurb states "optimal protection from rodents and martens". Has to be pretty tough as the latter can eat through almost anything.

I had to look up what a marten is, something new every day!

I doubt it stops the chewing as such, probably more makes it taste horrible to them.

 

[sparksfly]

Personally I would go for flexi conduit with metal boxes in thatch.
You could replace sections of wiring over time, metal junction box over light position on noggins. There maybe parts of the wiring with internal damage. SWA could work except for urine damage once stripped.
Inspect the wiring every year or so or/and have an electrician test upstairs light circuit only periodically to cut costs.
I passed a thatched EICR recently t/e everywhere, no damage in the last 20 years, another non-thatched had severe rodent damage in a small area 8x heavy duty jcn boxes later bits of cable, after squirrel access blocked. If it were regular occurrence I would go down the flexi steel route. BTW cables were stripped completely in places, no tripping, no dead rodents... a builder noticed it after working up there.... as someone else said 2 MΩ is still a pass but a visual is just as important.

 

[Mick-J]

Thanks @sparksfly
I had a brief look yesterday (before realising a dust mask might make sense).
All wires looked pretty tidy.
No signs of chewing visible.
One junction box I could see - no signs of any activity.
I will get back up later and do a more thorough check. I feel like a watching brief might become an annual activity for us.

Be nicer to get the safety check done this end of the season so we know we can let it next season, but our Ts&Cs mean we can disappoint people by cancelling if we absolutely have to (fingers crossed we don't). Our sparky wasn't so keen to repeat the tests/certificate so close to the last one

Cheers all.

 

[pc1966]

If the cable looks clean, dry, and not munched then dirt or water in junction boxes is the next obvious thing to look for that does not involve ant special skills or test equipment. Just some care and making sure the power is off first.

A simple voltage tester might be a good investment if you are likely to poke around things. I have one of these, but you can get a range of them from Toolstation or Screwfix as well:

VT12 Voltage / Continuity Tester

Excellent value LED voltage and continuity tester

www.cef.co.uk

 

[Mick-J]

Thanks - I do check for volts before doing ANY amateur electrical work
A related aside.....our electrician does appear quite keen to NOT do any changes, because he would then have to ensure the entire cottage is up to current specs....
.....although he is quite happy for me to change things where needed.

Simple example - he is not keen on sockets with USB built in - they are permanently on, will clearly add a little resistance, and (in his view!) are often cheap items subject to failing. We have three dotted about the cottage - handy for guests to plug into - but he suggested that whilst he might have them at home, he would always discourage them in a holiday cottage. I will probably change them out (anyone strongly disagree with him?).

I wonder how many people perhaps use 2 sparkys - one for the certification, one to actually do work
I type the smiling emoji, but I am semi-serious......

 

[littlespark]

A sparky that does work should always certify whatever they do….. but only the circuits they have worked on.

You can get any sparky to do an EICR, which is a report (not a certificate) on the condition of the electrics of the property, covering as many circuits as you want.

It’s not normal for one spark to do work, then a different one to certify the first ones work.



USB sockets; I used to think they were cheap and nasty… but I’ve fitted one in my own house, plus a number for customers over the last few years and never had a failure.

 

[Mick-J]

Thanks @littlespark
So if you did something on one part of a house, are you NOT liable for ensuring the rest of the property was brought up to current standards?
He was suggesting he would have to

 

[littlespark]

Thanks @littlespark
So if you did something on one part of a house, are you NOT liable for ensuring the rest of the property was brought up to current standards?
He was suggesting he would have to

No.
He only has to ensure that his work is up to current regs….

For example, when RCDs first came into the equation, many electricians added a second mini consumer unit to cover what they were adding or working on, leaving the older fuse board untouched.

 

[Dustydazzler]

I still here it all the time on site that once a sparks touches any part of the old wiring we suddenly become responsible for ALL the wiring in the property

THis is simply not the case

Its like saying a mechanic changes your break pads and is now responsible for the workings of the entire car

 

[pc1966]

USB sockets; I used to think they were cheap and nasty… but I’ve fitted one in my own house, plus a number for customers over the last few years and never had a failure.

You can get cheap & nasty for sure, just look to fleabay, etc. But the better brands of sockets ought to be fine.

I vaguely remember some had switching so isolated if no USP inserted (as opposed to live all the time) but don't remember the brand(s).

 

[nicebutdim]

I vaguely remember some had switching so isolated if no USP inserted (as opposed to live all the time) but don't remember the brand(s).

Think MK produced a shuttered grid unit that isolated when shutter was closed.

Would be great if manufacturers could produce usb outlets that only powered the transformer when plug was inserted.

 

[littlespark]

i bet there are thousands of proper charging adaptors plugged and left switched on across the country. Even the lead plugged in. Just no device on the end.

 

[pc1966]

i bet there are thousands of proper charging adaptors plugged and left switched on across the country. Even the lead plugged in. Just no device on the end.

Indeed they are

Fire brigade, etc, all advise to switch off when unused. Saves a small bit of electricity cost as well, and no doubt makes the device last slightly longer. But that requires folks to think and act.

 

[Mike Johnson]

I admit that I thought they did not draw power if not plugged in, bit of thought now makes me think otherwise, the step down transformer or whatever it is must draw some power. Wonder how much power a shaver socket uses over a year.