Celotex!! Electricians worst nightmare
2021 ж. 2 Жел.
86 600 Рет қаралды
2000 likes and the most like comment I will purchase for a video
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Where did you get the pole for mounting the laser level?
Review a ridiculously expensive cable/stud/pipe finder. Always wondered if they're worth the money.
no, just use your hand
@@croikeymatesthrowashrimpon8130 or use your X-ray/ heat vision
and a cheapo version
I've had a few and they are all odd. My current go to is a combination of Flir thermal and a ancient Bosch one. So yeah I'd be up for a test of stud finders.
@@mo6088 just guess, and throw away any of the patches you take out, its now the tapers problem
Too late on this one, but the answer for "how to do this next time?" is to walk away from jobs like this one. Plain and simple, this is a badly designed roof that will sweat and mould in no time at all, particularly given the usage. It's deemed as a 'cold' roof and it has to have a ventilated void above the insulation to stop moisture forming on the underside of the plywood/osb boarding. You have unwittingly made this worse by forming the channels and holes through the insulation as these will form passages for warm air which will then condensate when it hits the cold underside of the timber sheets. Liability wise, you have changed how this roof works now and the 'builder' who put this together can point the finger if there are any problems later down the line. If it's a cold roof setup like this one, then you need to ask for a service void to be formed below the insulation layer. Clearly in this arrangement it doesn't look like you would have the height needed to reduce the ceiling level, but again it points to the project being one to pass up next time. Please don't read this as an attack on what you have done, it's not intended as that at all, just to advise you that it's not worth getting involved with this type of project again. Save your energy for worthwhile projects which are well designed. For context, I'm a Building Surveyor and I've been designing extensions for 20+ years trying to avoid problems like this.
I’m about to qualify as a spark and upon seeing his situation with the Celotex ceiling, I asked myself whether or not it’s worth even taking this job due to the regulations regarding the void above the celotex and your comment has helped a lot so thank you!
@@dreamer-2972 I've never met a sparky who has no work, they have always been busy and in demand, so there's no need to take on jobs like this as there's more than enough work to go around without opening yourself up to potential legal issues. Good luck on finishing the qualifications!
correct. u need an air gap between roof and insulation in addition to a vapor barrier on the underside of the insulation. Also cutting in down lights in is a big mistake.
I was just about to write this in the comments, I’m a roofer, good job buddy I hope they listen to you.
It’s still a cold roof if it has vented soffits and there is a vented up stand at the opposite end that is if the solid bridging is allowing a 50mm air flow gap and or the furring strips are allowing a 50mm airflow gap, his issue is with the chasing out the celotex which is losing the Uvalue of the pir insulation that had been installed prior to his arrival. What he should of done was ask the builder/ customer to remove the celotex he could then drill a hole through the joists within the spacing of the air flow gap thus no reduction on loss of the Uvalue by cutting the pir insulation.
Hitachi magic wand, would love your opinion
Makes a nice frothy latte...but needs a massive cup....
Surprised there's no 110V version available for safety on a wet site
I use LED round panels in cellotex. They are only around 12mm deep but you do need 25mm void for the driver or locate them somewhere else. This means you can install and not cut the celotex at all you can either get the builders to counter batten they ceiling or if enough depth in the jousts push the insulation up an inch and still retain air gap
That roof will sweat and mould. The air gap needs to be externally ventilated to allow condensation to escape. Even if it's ventilated at the fascia, this roof has noggins that prevent any ventilation in the central section and trap moisture in the cold gap.
That was my first thought as soon as I saw the thumbnail! Though I know it's not Nick that's doing it.
My thoughts too….particularly within an environment which will be warm and likely humid for much of the working day…..but hey, that’s not Nick’s Issue….but perhaps suggest to the client some additional ventilation in the space, wired through a humidistat…? Or at least leave provision…?
That's what I were thinking too
Obviously done without planning permission which is required if the outbuilding is being used for commercial business. That roof is a mould magnet hope them light fittings are waterproof.
Depends wether its a warm or cold roof installation, its possible that the new roof is something like warm deck and this insulation has been added to upspec its u value
Brilliant work and thanks for sharing this with us take care
yes an air gap is required condensation being the culprit. I have had the same problem with my extension with a vaulted ceiling and did plum for 175mm 7" rafters to allow for 1.5mm wiring and eyeball downlights.
I feel your pain mate, I have just finished a large wrap round extention with 50 downlights and the lot was celotex.
Great work luv the contents given, by the way where can i buy one of those kneeling mats you have?
Yes you need a 50mm air gap to meet building regs, it stops condensation & thermal bridging .normally you would fit timber spacers to maintain the air gap and to stop it being pushed up also the PIR is then covered with a plastic vapour barrier before plaster boarding.
Try the rubber door trim it’s metal grippers inside instead of gromit strip when cutting out the back of a fuse board, the metal inside bites down onto the board and it stops the issue of the cables knocking the strip off the cutout when pushing it back to the wall or adjusting the cables neatly when stripping and terminating them
The DeWalt sparky stapler or if the new Milwaukee one does insulated staples then that one instead?
I sure hope it's better than the spring operated cat5/6 spring operated stapler, it's failed to put the insulated staples in roof joists every time, the Arrow T59 really puts it to shame' I specifically bought the milwaukee stapler for fixing cat5 cables for a cctv cable in a loft area... total waste of money. Worst Milwaukee tool I have ever bought, and I have maybe 20 plus of their battery tools.
that dewalt cable stapler is one awesome bit of kit. i've been using mine for a year, not only does it save loads of time and busted fingers, it also saves space on the clips as it will do most common cables with the same clips
Great to have a vid to watch on a Friday. 👍
I know this is almost a year old but having just rewatched it because of doing a similar job in a kitchen extension, I decided to save myself some work and just pull the cellotex run my cables and then push the cellotex back into place so my cables run along in the void
Warm Deck - The type of insulation for this is usually of a rigid type and the thickness will vary depending on the manufacturer’s specifications. This is placed over the roof joists and an board (normally external ply) is laid on top. (Thickness varies according to the manufacturer’s specifications). The roof covering is then laid over the ply. Cold Deck - The thickness of insulation required will vary depending on the material you decide to use and the manufacturer’s specification. A ventilation gap, usually 50mm, should be provided between the top of the insulation and underside of the roof covering to allow the air to flow across. Ventilation openings (either at the eaves or upstand). A vapour membrane should be added to the underside of the insulation and tacked to the joists before applying the plasterboard.
not popped past in a while....good to see you back on track pal.
As far as I know and if I am correct, air gap of certain thickness required between roof and insulation, this to prevent touching cold surface (roof) and keep heat down.
Set your lazer up for the centre of the box, you can drill directly through the holes, no need to draw round boxes or mark fixing holes
As E-fix and the lovely guy who happens to have the best shit-eating-grin that I would love to have, would say… “top tip”.
love the video Nick, quick question im currently doing cable calculations in college and you touched on that topic in this video. I was just wonderin how often does a spark realistically do cable calculations. Cheers man
Domestic electrics not very often but commercial/industrial electrics quite often
Dewalt cable stapler. I love it would like to hear what you think ov it
Nick test out the Ferret Plus with voltage detector camera record on memory card & variable lens focus, I got one could send if you want to have a play, as I have not seen a UK electrician review on one yet.
I would be concerned that by removing all of the insulation above the spots you have a cold surface and warm air might condense. You could have cut the circles out but pushed the insulation up to create the pocket, it could be trimmed down if you needed more space, you might have done this but it wasn't obvious in the video. The Luceco fire rated lights are designed to work under insulation. 1mm would have been fine, it's still good with 300mm of fibreglass in loft spaces and that's with much more load on the circuits. I wouldn't have been so concerned with the cable being in direct contact with the foam and you could have run the cables above the insulation, with so much focus on energy efficiency and airtightness I would want to avoid destroying the foil. Thanks for the video.
Air gap depends on the type of roof. Warm roof or cold roof.
I have been told by the DS that cutting downlights in celotex causes cold spots. He made me remove all the lights on one job replace with low profile downlights and add insolation above them. Nightmare !!!
Think of it like a small loft above PIR boards (celotex/kingspan etc) I run above and drop down hole for downlight no different to normal house :)
That roof and insulation is wrong wrong wrong. Do what you want it with Celotex it will make no odds the joists and roof deck will sweat and rot out anyway. There is no provision through rafters and each section of the divisions (noggins) essentially creates a whole load of zero air flow compartments. They should have also added battens at Celotex thickness to stop insulation being pushed too far up - but as I said it’s a complete dogs breakfast - fit two big exhaust fans to blow the moisture created by the business out of the building to reduce moisture entering roof space.
Assuming that's a flat roof above it; the celotex should be taped together along the beams to create a vapour barrier. It then should be ventilated above it to stop condensation forming on the inside of the cold roof. If I was you I would have pulled the celotex down where I needed to run cables and put them in conduit above the celotex in the ventilation gap.
☝ yes, should not cut the insulation vapour barrier (foil facing).
Hi mate, I see you have a little hook on the bosh 12v impact can you please tell me from where I can have one, appreciate💪
You're right about the maccies in stafford, there's 4 now isn't there? :'D Quality video as always
This is a great idea. My suggestion is that you should review a product which electrician needs. Test it for its reliability. I recommend you testing a voltage and continuity tester (preferably open jaw) from a reputable brand like Fluke, Megger or Kewtech
I think you should setup a consumer unit and tighten terminals with a regular screwdriver to guestimate the torque and then go over it with a torque screwdriver to see if you were accurate or not. Like a bit of a competition. Start at 1nm and go all the way up to 6nm or whatever the highest setting is on yours (mine is 6nm). Some EV chargers and other things specify quite low torque settings that people may not pay attention to and I think it would be interesting to see what you think the torque should be compared to manufacturers recommendations. Maybe I'm sad 🤷♂️
You just literally think of the most boring thing you could lol?
I dream about this stuff
For a tool review, I thing you should try and do a day using only Amazon basic tools. I think it would be quite entertaining.
Regarding the insulation you need a cap between the roof and the plaster board so you get warm air below and cold air above this stops condescension getting through to the plaster boards I only know this becusse I built my own summer house and got really bad condescension good job I didn't fit the plaster boards till after I moved the insulation boards also I would try get the cables in before in the cold section of the roof
Cold style roof needs ventilation above the insulation, usually weep vents or it will go mouldy. I would have run the cable above the insulation (because by channeling it you have reduced the cellotex efficiency, it also keeps the cable cooler. Having said that, 8 LED lights will barely raise the temperature of the cable, even 1mm2) and use 20/25mm steel conduit couplers in the joists for protection. A pound to a pinch of sh1t the plasterer will go through it then you will have the hassle to sort it.
There should be side to side AND front to back ventilation above the Recticel, with the air gap on the cold side. This will ensure plenty of ventilation above the rigid insulation to prevent the formation of damp and mould. I would never install recessed lighting in rigid insulation: The whole point of it is to insulate the building by separating the cold side of the roof from the warm side. Cutting loads of holes in the insulation negates that. I would only install recessed lighting in a ceiling below a warm roof. Then there is no insulation near the lights to worry about. The insulation in these roofs is above and away from the ceiling. In this case, I would install LED track lighting on the surface of the ceiling. I would not worry about upgrading to 1.5 because the CCC of 1 milli in conduit and insulation is well in excess of 6A.
What is that extendable pole you have for laser please as I always end up banging a screw in wall on opposite side
In the back box’s I always use both Vertical fixings, personally find it easier
Derating the cable - In this scenario I'd be doing the same. Some places we've done lights in 2.5mm because the cabling was fully surrounded in insulation. We ran IC4's and temp tested.
This is what has been dubbed a ‘hybrid roof’. The idea is that you have a small void between the OSB and insulation panel. You then put a vapour barrier up followed by plaster boards. Low profile or even surface mount light fittings are used. The idea is to keep the building height under permitted development rules (although that may not be an issue here as it’s commercial use). Take a look at Oakwood Garden Room’s channel. He uses this method exclusively and you can see how his electrician does it - the run lighting cable along the joists rather than across, also only partially cut out spots
The calculations that Oakwood Garden Rooms are for low use, this is a mini hairdressers so plenty of water and hot air hair drying. All that moisture in the air will condense on the cold surfaces on cold days unless they have a large amount of air extraction and pull in the less moist air from outside. This screams no building control approval and no planning approval (change of use).
@@davideyres955 I see your point. How do you feel about people doing what they want with their property, even if they have their property rot as a result. As long as it doesn’t hurt anyone. My point being, we have too many regulations and fools should be allowed to do what they want with their own stuff if it doesn’t impact third parties.
They should have built that as a "warm roof". The insulation sits on top of the joists and you've got all the room underneath for cables and pipes
Hi Nick, Fab vid! ... how about doing a review of a heat gun and some heat shrink? I know some people prefer to terminate into a stuffing gland one end of an armoured cable with heat shrink over the steel wire. For example.. Storm gland the armoured end at CCU/Wiska and at the EV charger end terminate with a stuffing gland with heat shrink. What are peoples thoughts? if heat shrink is preferable (one end only of course), it will be nice to know a good heat gun? Electric? battery? best shrink? can get 2:1 - 3:1 shrink. Will be nice to know a shrink size that fits nicely on certain armoured sizes etc. I know Artisan do some heat shrink and also Oval for their storage batt installs!!
so the roof you got there is a cold roof as insulation is on the underside of the roof. normal cold roofs you will have a minimum of continuous airflow gap (above insulation) airflow will need to be allowed to enter and exit at both ends. I have seen a hybrid cold roof which the insulation is pushed tight to the underside of the roof and all ends insulated (haven't yet studied it). also a warm room will have insulation on top of the roof. hope this helps. vapor barriers really help when cold roofing.
Hybrid roofs are only ok for low occupancy rooms like something your not going to spend every day in, maybe just an hour or two here and there. Even though they seem like they should work i'd still question using them for anything more than a shed and even then you might as well use a cold roof.
Slick haircut Adam! ......and, did you just say a shower, RIGHT above a fusebox?
Set your laser for the socket centers it makes it so much easier
I'm not having a go at you when I say this, but can I suggest that whatever you do buy, maybe buy from somewhere apart from Amazon and help support other smaller operators if possible. Thanks.
If you ever want to find out about the regs with insulation the document your after is called Approved Document B As some one who used to audit installs, almost no one follows them, the regs for the insurance are often stupid and unless you do it absolutely perfectly you arent going to get any where close what the barrier rated maximum is.
Wiha Speede II For work, try to install new sockets with flexible conduit terminated inside the socket and terminate the conduit inside the consumer unit. This allows you to just pull wires through the conduit all the way Also, I need some tips for how I can convince my boss to allow me to get an impact driver.
could also just use singles if using a full conduit system
Review please Wire Stripping Twisting Tool 3-Way 5-Way Wire Stripper and Twister with Extension Adapter Attachment for Power Drill
Hey Nick you’ve gotta try an aegis cable tracer. Fantastic for finding a cable run on de energised circuits
A really expensive data cable tester / certifier, could use it in the unit to experiment with putting data cables next to power and see what effect it has
Can you review the latest ( bathmate ) extra large version please.
Get one of those thermal imaging cameras, so you can look at the heat of cables in wall/floors, and boxes. Be interesting to see how a short or faults or heat is loaded across a circuit from light to switch to fuse board. Even possible to find live cables.
He’s got one. See video history
Think you should check what a cold roof is (that's what you have btw) cutting out the celo has made cold spots that will make damp problems in the future, you should have done a complete surface installation for the lighting and the customer should have been advice by the builder that a warm roof was needed it wouldn't have cost much more leaving you with open joists
Lever pipe bender, to see if you can use it with a spring to get decent bends on pvc conduit. And if you can bend metal conduit with it... Always wondered but never bothered buying one to see..
I did a plumbing course years ago which we filled pvc pipe with sand, heated it with a gentle flame (not blowtorch), being careful not to let it blister, and bend it while it's soft to the shape you want. Probably do same with conduit. No need for a pipe bender, the sand keeps its shape.
@@ade7163 Yeah I don't think I would make any money if I made each bend like that, a spring is fine for stopping any wrinkles, I just wondered if introducing a pipe bender would make a nice bend as I find sometimes my bends can be a bit tight and once the conduit has started to bend in one point its hard to get a more sweeping 90 degree bend..
Needs an air gap. The air gap stops condensation. Also, the gap should be ventilated & I’d usually put a layer of DPM above the insulation. Plasterboard screws are 38mm with 12.5mm of plasterboard, the screws will recess at least an inch in. Anything less than 50mm really needs protection from mechanical damage. Stud plates work. Try using a Multicutter to channel into the board & seal it after you. The cable WILL be derated by around 50% so should be using 10mm2 for shower, 4mm2 for sockets & 1.5mm2 for lights.
Hi Nick. Bit tricky to see the whole roof design but the regs are You need a 50mm air gap and ventilation through. Just having 50mm is no use since the moisture won’t be able to be taken away by airflow. It didn’t look like there was that in there so during the cold your likely to get moisture build up and then the wood will rot. It does depend on use and how much moisture is going to be in the room so anything like shower or cooking are high moisture. Cutting the channel is probably going to reduce the effectiveness of the insulation by quite a bit. It’s likely you’ll get a gap between the bit you’ve pushed up. Probably end up with a cold spot on the inside ceiling and possibly get mould build up. The important thing is to have as good moisture retardant barrier as possible. The downlighter will leak air and if that is above the celotex then that will condense badly and it will literally be dripping wet. If that’s a flat roof then they should have a warm roof where the insulation is above the roof deck. If it was me I would rip out the celotex totally and redo the roof above. Might as well do it now rather than wait till the roof collapses.
There is no cross ventilation so the best thing to do with it is fill it completely with insulation with no air gap above the insulation and the put a vapour barrier over the entire ceiling . It needs to be as air tight as possible . The whole thing has been done wrong and it is a single skin wall ,you will need a 100mm of celotex on the walls and a vapour barrier , plenty of heat and ventilation plus keep your fingers crossed you don't get mould
Here's a query. I know polystyrene damages T&E but does the foam of PIR Insulation also affect the plasticizer's in the T&E cable too??
Nope it's fine.
Would it not have been possible to run the lighting cables above the rig board on top of the wall and running to each light from there with conduit against the osb and rafters fixing to the rafter in the top corner above the installation then you wouldn’t have to cut the installation apart from for the lights coming through
Test the accuracy of the loop test function of the kewtech loopcheck 107 mains socket tester, compared to a more specialist tester.
What size all round band do u use ?
Try getting those downlights in after the ceilings up. How are the spring arms going to open out? Done this before! You'll need to chase out a grove to let the arms fold out.
Holes he’s cut are bigger than the downlight hole
from what I can see. This is a cold roof as celotex is 6cm from timber sheeting, no evidence that its not vented, noggins could be 97mm x 47mm allowing air gap. Also a thermal plasterboard may be used to finish the ceiling and a vapour barrier is allowed on the underside of joist. However the exterior walls are only 100mm so no cavity! To fix plasterboard to the patterns will not meet the u values. Agreed cutting into the celotex for cabling or as stated fitting lights is not an option.
This type of insulation unlike polystyrene doesn't break down the cables. When breaking the barrier use expanding foam to reseal. Electricians need to walk away if the roofs are not constructed correctly for electrical installs. And builders and planning department need to know how the electrical installation can be incorporated in to this insulation construction when constructing the ceilings.
Always been told to take it off the backside cut a channel as you need the airgap
Tavismanor MeterMade 25 Smart Meter Cable Stripping Tool Stripping tool for tails to correct length
Great fix to a small shed business
It's a cold roof construction done not very well, needs 50mm gap for continuous air flow to prevent moisture build up. If you have blocked air flow you may get water vapour condensing and entering your fittings plus mold build up too. If they had put firings in and battens at 90 °to firings you could have put your cables above joists between battens etc. where was building control on this one.
Where can I get one of the poles for mounting the laser level?
Put the cable in the middle of the joist first, then Chanel out the insulation to fit the cable in side.
U are Correct about the air gap u should all way have at least a 100mm air gap to allow for it breath
The new fein multi master multi tool I think it’s a lot better than the bosch one and I think you should give it to Adam
That's why I use 20mm (or 25mm) corrugated flex conduit pipe whenever I can... even in wooden frames. English electricians laugh when they see me doing it (it's more or less standard in most of mainland Europe) but on proper rewiring jobs that's the way to go. Once you master handling it it's really quick especially when you work in pair. Believe it or not in same cases even quicker than clipping cable (especially when you have double isolation like in your case here). If you have double isolation or lowered ceiling you go with screw mount cable ties or those masonry knock in mounts + cable tie in each joist, than conduit and cable (of curse lubricant is sometimes useful). Than builders can work around it with second lair of isolation which goes on top of joists. And it can also go through the joists... you just use 22mm bit fore holes and than you don't have to sweat when it comes to isolation. Also it's a life saver if you mess up something or if you have a customer which likes to change things every now and than (and lots of clients with money are like that). It's not once that I had a situation when I had to pull out cable and go with different one (3-core instead of 2-core or bigger diameter ect.). In one case I had to pull 2 new lines each long between 10m to 15m under the screed and up the wall and that alone justified the cost of flex conduit on that project.
Indeed!I am a dutch electrician and those conduit pipes makes changes very easy!!Esspecially when they end with a box in the ceiling.You just run the spring through,connect the wires or wire on it and chase the wire/wires through.
I did that when gutted and rebuilt our current house between 2013 and 2017. Professionals mocked as not necessary but electricians came in and said "Electrician's dream". Regretting those short sections where I didn't use conduit. Also used 1.5mm for all lighting circuits and smoke alarm circuit. Wish I'd used 4mm for loft ring which is about 90 metres long
@@cuebj why do you wish you’d used bigger cables ? I only ever use 1mm for lighting /6A circuits perfectly adequate. A 4mm ring ?? Nonsense. and why would you have a final circuit of 90M ?
A “cold roof” (which that is) needs through ventilation through the soffits and noggins. No way the building meets the regs at all!
Also needs a vapour barrier as soon as the spark cuts into the silver foil vapour barrier destroyed
DeWalt clip gun
Yeah , can get dewalt to Bosch battery adapter so can use the same battery’s 👍
Could you have ran your cables in the void above the insulation?
Need to know if it’s a warm or cold roof or ask roger
I would have run the cables at the top of the batons , sod cutting slots in the inso
How about a review of dry core bits
25mil gap otherwise it will sweat plus if any water leakes tho it wont touch it will run down the wall rather than soak it bit mad its on the roof tho kingspan is normal for internal walls
Goodness - I had no idea there was so much money to be made from these videos. Very tempting to get started.
It’s not as easy as you think. I wish you luck. I have thought the same but can’t face the hours and effort with three young kids.
Hi nick love the videos keep them coming, Dewalt flexvolt wall chaser not many reviews on it but I have had my eyes set on it for a while
Cheap insulated screwdrivers pliers nd long nose and snips set off screw fix (always wondered on them)
"Get off my Monster!"
Dust pan and brush reviews 👍🏽
Milwaukee Packout, full set with draws
Tools tour please
I would like to see a video where you get another random person for a week rewire (me) as in the trade but kinda just starting out.
Please buy/review A thermal camera and show some connections under high current.
JW does stuff like this - heres a recommended viewing - kzhead.info/sun/maWriLxlrGmrq6s/bejne.html
I’ve got one bud 👍
Surely you could have ran the cables 150 m max from the ceiling around the perimeter not through the ceiling like usual. Not cutting the celotex. Just a thought. Good channel I’m a 50 year old sparks mostly industrial. Researching for my lad who will be working with me next year. Anyhow good content I’ll be putting you on subscribe for my lad to follow.
cables should have been put in before the celotex was fitted and clipped up to the top side of the joists where there is the 25mm air gap
A classic case of a subbie cocking up the builder's work! Cutting big holes in the insulation and then not repairing the breached insulation/condensation layer will mean that the client can expect some serious issues that will affect the electrics and/or the construction of the building. It was very unwise to install downlighters, no matter what the client may have wanted, without creating an insulated and vapour resistive casing over the unit. If downlighters were to be installed then the casings should have been constructed at the time of the insulation installation. Ideally, downlighters should not have been specified because of these problems, which in my experience is well known in the competent sectors of the industry. If the installer was unaware of what to do then he should have consulted the designer, perhaps even the builder if he was knowledgeable, or Building Control to simply bash ahead with the work would be seen as negligent in legal circles. I trust he is well insured against claims? Also, I would have thought that downlighters would not have provided sufficient uniformity of light in such a low ceiling space and that will not be suitable for hairdressing unless additional lighting is provided. For hairdressing I would have expected a minimum of 250lux average at the working plane i.e. around 1.2m above FFL with good uniformity. I assume that the building has a flat roof, in which case it would have been better to construct a warm roof with insulation above the deck.
Top post.
Buy a large pipe reamer and test it on Adam 😁
13:02 cables out of zone too what looks like a cooker switch sorry lol its only just out neat job by the way
Maybe a jet rack for inside the van?
expanded foam deteriorates wire insulation
The vapour barrier stops warm air going into the roof and the insulation stops condensation. If the insulation is not pushed up tight to the roof the air has nowhere to move (ventilation).
Not quite correct. The vapour barrier slows the progress of moist air into a space. The insulation reduces the transfer of heat. The problem is air will contain a certain amount of moisture for a given temperature. As air gets colder it can only contain so much moisture and it wants to condense out of the air. Generally this happens on a colder surface and you get water beading up. It can also be inside insulation and it then gets damp and become less efficient. The problem is when this happens on wood which then gets mouldy and rots and then loses its strength and you have a collapse. Hopefully this is just the deck and you get a sagging roof and the waterproofing fails and you get a leak. Worst case the roof collapses and people are injured.
@@davideyres955 Hi David When you say the vapour barrier slows the progress of moist air into a space. I believe, the vapour barrier stops the progression of vapour. Then the insulation protects the cold surface from any warm air being able to touch it and start the condensing process, that will rot the roof. I have done this with all the extension I have build over 30 years and, I have never had to go back to one ever. Again, I believe that stopping the water rich air getting to a cold surface is the key to stopping rot setting in. Maybe I am wrong...but my experience tell me I am correct. However, I do appreciate your view.
Oh, Just to add this would be a warm roof. A cold roof would be different.!
The roof will sweat if there is an air gap between the insulation and the roofing board. Unless there are vents the the insulation needs to be pushed tight against the board. It's called a highbrid roof I believe.
It’s called someone not understanding how to build roofs. Hybrid roofs are ok if you do the calculations and this is quite complex, it depends on how much moisture you have in the air in the area you have. You want a low humidity environment for that and this is going to be a hair dressers so quite a bit of humidity and a hybrid roof is a bad idea. They will need either an industrial scale dehumidifier or a way of exchanging the moist air with outside less moist air and then heating it up otherwise it’s going to be like it’s raining under the roof deck.
All those noggins are pointless. The ceiling height is too low anyway, but there should be an air space with free air flow from end to end, deeper insulation and joists, and ideally 400 centres for strength. Then you could staple a vapour barrier across the timbers, fit counter battens to run the cables and then plasterboard with a vapour check backing. But that's just how we would have built it, after 40 yrs experience.