Joist Drilling Do's and Don'ts: What You Need to Know
Getting a cable from A to B is simple... right? Did you know that if you drill a hole in a joist in the wrong place you can weaken it? Or that a building inspector can refuse to sign off a new build if holes are in the wrong places?
Guest presenter Ross Howell takes us through the positions where we can drill a hole and where we can't, giving us all the information we need to know to keep our electrical installations compliant with BS 7671 and the Building Regulations.
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00:00 Drilling holes in joists
00:20 Building Regulations Part A
00:35 BS 7671 Regulation 522.8.14
00:59 Structural Engineers Take Note!
01:27 Rick's Tool Time: Mandrex Ultimate SpeedXbit & Ultimate 4X PowerXbit
02:07 IET Guidance on Drilling Holes in Joists
02:55 Visual Examples of Where to Drill Holes in Joists
03:54 BS 7671 Regulation 522.6.204
04:06 BS 7671 Regulation 522.6.201
04:21 Quick Maths!
04:50 Calculation for Typical Span of Joists
05:09 Catastophic Results of Drilling in the Wrong Place on a Joist!
05:40 How to Avoid Lifting Boards and Finding Pipework
#drillingjoists #mandrex #electricalinstallation #electricalwiring #electricalwork
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Too expensive. I’ll stick with screwfix auger. Everything you promote is so expensive like the £800 crimpers.
@@Wawaw738 Can't find the items anywhere much. Says City Plumbing for me and a search on there shows nothing.
Then the plumber comes along and bangs in a 40mm waste pipe notched out.
You have a great point 👍🏻
Yip that’s us
With a fall on it so each so each notch gets deeper
Oi... we have gravity to deal with. You cable monkeys have it easy.
Yep 😂😂😂
Ross was my teacher at hopwood and the best electrical teacher i had top guy👍
Wow, wasn't expecting such professional advice here. So glad i came across your channel. On to the next video of yours!
Welcome aboard!
Fantastic content as always great work Ross 👍🏻
He's good isn't he? 💪
Re-wiring my son's "new" 1929 house which had knob and tube wiring.The place is built with "real" 2X lumber without a single knot visible. We're using old holes almost exclusively even if it makes our runs longer than otherwise possible. Just trying to use common sense but I'm just a dentist and he's a Physical Therapist. Thank God for KZhead(...and my best buddy who's an electrician).
I will not even be doing anything this ever probably, but great content. Love it.
Thanks very much for watching! 😃
Yet another regulation that we have to bear in mind. I’ll keep this thought at the bottom of my full to the brim electrical brain. No other trade has to endure and tackle so many areas within that trade. I think we should strike for a pay rise. I’m should have studied to be a surgeon.
Search for a job as a technician, lots of companies want electricians as a base for that. The pay is often much better and you don't have to work/touch on so many subjects. I did after working 22 years as an electrician and never looked back.
Can I ask what regs apply to plumbers and the copper pipe they install. I have seen large cutouts to joists for the installation of several copper pipes under a floorboard.
We was always taught it’s better to try not to drill holes in the centre of the room and that’s the weakest area of the joist ,best near the ends where it’s supported. A good tip . Never drill a hole in a joist unless you know what’s on the other side ..ie pipes and cables
We were.
Wrong! Notches are positioned at the ends and holes are drilled in the zone that begins at one quarter span
The advice on where to drill holes in the centre is wrong. A joist is in compression at the top and in tension at the bottom which means that, there is a point (called the neutral point) where these forces balance out. By drilling at the "neutral point", you are taking out material that is mostly not in tension or compression and thus not providing support. Of course as you move away from that neutral point, the forces of tension and compression do become out of balance, which is the reason the hold diameter is regulated. Unfortunately, where the position of the neutral point is varies according to the distance along the beam from the supported ends. However, it becomes close to the centre line in what is called the "safe" zone between 25% and 40% percent of the joist length from each end. Notching (on the top) can be done towards the supported ends of the joists, albeit to relatively shallow depths. However, all this has to be put in perspective. A hole drilled for a single 2.5 mm^2 cable drilled on the centre line anywhere is really not going to have a substantive effect on a properly sized joist.
Really you shouldn’t ever do it. You should run a conduit along the perimeter or between the joist. But that costs extra money for the contractor. He doesn’t care if you have wobbly uneven floors in 30 years. He won’t be around.
What happened to college tutoring, you was the best tutor we had 👍
I moved into a house, where i had to get repaired a load bearing joist, that had been hacked by pumbers to get the hot water pipes in. They had removed 3/4's of the joist and the landing had a spring in it, also there was movement in the ceiling..... So these rules need to apply to all........
They also apply to plumbers!
@@efixx plumbers have a much bigger problem than electricians. They are generally dealing with much larger holes and inflexible pipe work. Also, water doesn't like to flow uphill, unlike electrons that don't seem bothered about it.
@@TheEulerID Yes, but structural integrity is of primary importance. Plumbers don't just get to cut whatever holes they like just because some route is the most convenient for them. Need water to flow downhill but drilling a hole in the obvious place is going to weaken the structure? Too bad, you need to find some other solution. Oh what's that - there's no solution other than weakening the structure? Uh oh. That's really too bad. Somebody should have thought about this in the planning stages, and rectifying this is going to cost them money.
@@nathan87 you seem to have missed my point, which is that plumbers have a much more difficult problem to deal with. Electricians have it vastly easier when it comes to routing services simply due to the physics involved. In the real world, less than ideal choices sometimes will have to be made, albeit there are always limits.
@@TheEulerID this is true, but it just sounded like you were saying that having a more difficult problem justifies compromising structural integrity.
Thank goodness I'm only two months in to my apprenticeship, I'm jacking in and starting as a carpenter.
I am a software engineer, my professional organisation is also IET. (I am a member of IET too.) Watching this video makes me feel that software engineers are all amateurs in the field of engineering. I don't think there are IET guidelines on how we (software engineers) do our work. I was very impressed when you cite the regulations.
There have in fact been various attempts to make ISO and similar standards etc for software engineering. The problem is however that they haven't caught on; software engineering isn't really as amenable to standardisation as construction, as there are so many different languages and frameworks constantly coming and going, not to mention that the requirements of different projects vary dramatically. However, in practice there are most definitely many documents, canonical reference textbooks and internal standards specific to particular projects that fill the role of standards in software engineering (one common example would be Python PEP 8). It's all a little less informal than having a single ISO standard. But nevertheless knowledge of the such materials should be part of your basic preparation for working on a particular software project.
I’m a retired electrician. Over the years I have seen joists with huge holes and great notches cut out of them by various trades. Even if the regs are not followed surely common sense should play a part
Totally agree. A lot of remodel "contractors" want things done fast & cheap combined with trade idiots that know nothing and want to keep it that way.
On one job I was on the plumber drilled a 4" hole through a solid joist for the toilet waste, The building inspector didn't say a thing. I have been on loads of jobs, where plumbers have drilled right on the end of the joist and again the building inspector said nothing. Don't plumbers learn this in plumbing school, and do the inspectors know this, if I am on site with the plumbers they always ask me where to drill, crazy.
What about if the hole was drilled 40 years ago buy someone else? Do we use the empty hole that’s there or further weaken the joist by drilling a load more in the “right place”
On new install I would agree with the video. Actually on a complete renovation where access is more or less the same as new install I would again agree, especially of new joists to replace the old over notched ones were being fitted or they were being doubled up. On a rewire of a 1950's build house I would be weary about adding new holes myself in the "correct" location with existing holes already present unless these were going to be reinforced once services were removed.
Use the existing. That's the common sense answer and what I would do anyway.
Usually all the joists are the same in the floor of the house despite the differing spans. So ill vary the rules on drilling joists if i need to. An 8x2 spanning 1 metre could have a fair amount taken out of it
ONE MORE TIP: you've lifted a board and are drilling a line of holes to get across the room. You have to drill at an angle 'cos your drill and (auger) bit are too long. BUT your cables have to bend slightly to go through the run. Imagine a cross section of the floor, the cable has to zig-zag through the holes and are harder to draw in. FIX Alternate the side you drill from every other joist so your cable can run straighter and pull through easily
I can’t see many Sparks going to this much trouble ( Detailed measurements / calculations etc ) on every install , especially those that are able to use common sense and previous knowledge / experience.
You’ve just cured insomnia!
Great information but thats in an ideal world. I've never seen any electrician work any of those figures out before and of course the plumber just comes along and makes even bigger holes to do waste pipes.
sometimes you just gotta send it, especially in retrofit
I never use a circular saw for cutting floorboards but use a multitool instead!
A wise old plumber once told me, whilst a group of concerned builders were fretting over boring holes in some 2 story floor joists, either don’t put a bathroom on the 2nd floor or have the designer incorporate a chase in the design for the plumbing! He also said you can bad mouth the plumber but you won’t sell a whole lot of these houses without a bathroom! After a bit of discussion they finally decided that it would be ok to slightly over bore the joist in order to accommodate the waste line for the toilet! 😂
Slightly overbore? A toilet waste is 110mm in diameter (unless a masserator is used). Even if there are very deep 250mm joists, the regs would only allow 62.5mm holes without appropriate reinforcement. That's why placement of toilets and down pipes ought to be planned in from the start...
I would suggest that a lot properties built before about 1970 would not have 150mm deep host therefore drilling in the centre would not leave 50+ mm either side (above and below) the through hole and is therefore going to be non compliant? Good video though, lots of info
👍🏻
You're tarring a lot of buildings with the same brush saying pre-70s. I've worked on buildings from every century since the Domesday Book. I guess you're talking about some 1960s builds maybe? Other than joists in the roof space, or trusses if they are used instead of a cut roof, joists are invariably at least 6". Or certainly where I am here down south.
unless the spans are tiny floor joists will never be less than 150mm. Often you get smaller joists downstairs where the sleeper walls half the floor span but then you can just thread under anyway.
Jason Manford right there
I tend to run all of my cables under the carpet around the edge. This avoids damaging any floorboards or weakening any joists. Plus less disruption.
Any more tips? Lol
Yeah time is money 😂
Sky hooks
🤦🏽
The gripper rod has handy spikes to hold them in place.
You didn't mention breakout at the back of the timber which can be significant. If the regs are so demanding then any damage to the joist would be picked up - ideally joists should be pilot holed first, and then drilled from both sides. Btw the finish on the bits in the video is apalling - I used to make them - these have not been finished.
BTW. If using auger bits you can't drill pilot holes. Auger bits need to grip and pull themselves through the wood from the center.
@@RossMitchellsProfile yes you can - as long as the pilot diameter is not greater than the auger point. These auger bits with a lead thread are really only effective when used at a slow rotational speed - a brace and bit for example - a higher speed cordless would negate the lead effect of the thread.
yet, despite all the regs on new builds today. i will still choose my 200 year old house over them any day, and i am willing to bet my 200 year old built with virtual zero regulation. would still survive a lot longer than these new builds.
Plumbers should be taking this course. They are the worst culprits.
The joists in my gaff are 9" deep and 3" wide for a modest spam... you could put as any 'oles as you like in them and you'd do nothing to loose any structural integrity. However, anything built to a price which is anything in the past 50 years then you have to take note as will barely meet the regs before the sparky and plumbers start butchering them....Its the holes or notches right in the centre that do the damage with gravity doing its thing....
"it's the holes or notches right in the centre that do the damage" - huh? The best place to drill a hole in a joist is directly in the middle (height wise.)
By centre I meant centre of the span, not the width. the guides are quite clear that its the middle section of the joist that should not be bastardised in any form
@@guffermeister you can drill a hole in the middle of the span of a floor joist. That won't weaken the joist as long as it is in the middle of the width. Notching on the other hand is a different story. I suspect code specifications differ depending on jurisdictions.
Why not lower the ceiling a few centimeters and no need to do any drilling and weakening the joists?
To feed a new cable through existing non-compliant holes or to re-drill? 🤔
take a photo of it before using the already drilled hole, makes zero sense to drill another
If we look and interpret what we see... thickness.. depth..grain..etc.....you know.... COMMON SENSE.... that's all it takes
Lift floorboard, you can not find any property apply those requirement. So what the purpose of such unpractical requirement?
Eh? There's lots of properties this would apply to. Plus it's not about practicality, it's about keeping the joist sound. 🤔
He’s right, it is unpractical. Unless u pull the ceilings or all floor boards u in fact have no idea how long the joist are. Do they go full front to bk or wall to wall ? Given this a cable run would look like a S. It’s just tiring, stressful and pointless cos if u take the time to do the impossible, u won’t win the work or just make a lose. Plus if u did…. What about all the other notches and holes u can’t see. Class rooms great with fully exposed beams all the same length. or a one room loft install. but if far from realistic.
Still waiting for more Solar Videos. Please ☺
Coming soon
The title for this video should probably identify the specific country/location jurisdiction your recommendations and codes apply to, since it is available across the entire Internet, and should of course not be relied upon by people in different countries or jurisdictions that might have different building codes.
Luckily this isn't even a question for us living in sweden, as we build so called "installation walls" and just put the flextubes between the joists, so no drilling at all.
Would be good to see that in practice
Having lived in both continental Europe as well as the UK (now) I can safely say that in the UK domestic residential market very little gets constructed with either the need for maintenance or future need for modification in mind. No cable trunking/ducting, hidden plumbing, no plumbing access panels, everything is plastered and tiled over. And then they wonder why retrofitting new cabling and plumbing to improved building regs is so expensive here 🙄. In the UK a neat look definitely trumps future ease of accessibility.
Wise words
@@efixx I think Gaz should be sent around the world in 80 days looking at how wiring is done in different countries.
@@anthonybragg Gordon is on that case - kzhead.info/sun/nbedlq6ZmYd7iIk/bejne.html
Must is common sense but I don't get why holes have to be at least 1/4 of the span from the walls 🤷🏻♂️ back in the old days we were always taught to drill close to the wall and never near the centre, sounded sensible to me
it's clearly been tested and proven that the joist is least affected between 0.25-0.4 of span.
Sparks and plumbers smash the floor boards, cut massive notch then do their thing and say oh the chippy will sort out all them buggered joists and floor boards😡
We can only apologise on behalf of our entire trade... 😔
@@efixx No need to notch joists in new buildings, if there are strips of timber across joists like 45x45 mm, spaced approx. 600 mm apart, which the floorbards are attached to.
It would be most welcome if the chippys did the hole drilling, floor pulling for us. Then maybe they find out that gluing the bloody floor is not helpful.
@@sgfelectrical734 glued chipboard floors are structural
Great video and very informative, but the problem here is the real world. Time restraints, accessibility, no ones getting their tape measure and measuring to that degree. Use common sense, aim for the centre and don't butcher the joists!!
Or the bottom 80% of the joist is filled with insulation
Cool and all, but it's unrealistic in so many circumstances in an older house or even in a new one for stuff like downlights, and especially if you are doing data. I just put the smallest possible hole in the middle of a joist such as a 12 or 16mm or use existing holes, if the joist is thin it'd be better to reinforce it with some timber on the sides of it where your holes are, sure its not regs but there's lots of times that the regs are not possible to follow perfectly in the real world. Building inspectors don't really care if its obvious there's no other way to do it and you haven't made a very obvious weak point for no reason such as a 32mm hole in the middle of the span for a single 1mm t&e
Exactly......
if in doubt, always drill in the middle of the joist. That won't compromise the strength of the joist because there is pretty much no stress or strain at that point, unless there is other damage.
@@tchevrier Pretty much mate, and always the smallest hole possible too. Plus you want to be in the middle of the joist to avoid screws anyway, win win.
It seems to me that it would be useful to have steel plates with pre-cut holes, which could reinforce the joist whilst also providing a drilling guide.
@@andybrice2711 They make nailer plates to stop screws (only works when the top layer is plasterboard), but I think adding additional blocking to the area is probably just as good.
Very informative but never ever seen anybody follow this.
Surprised there isn't any guidance re. drilling holes through joists with respect to the position of existing knots. Wood cannot take any tensile forces through a knot, so if a decent size knot runs through the lower half of a joist, drilling a hole just above it through the centre-line of a joist would be a total no-no. (Really, there _shouldn't_ be any significant sized knots running through the lower half of a joist, but not all builders take equal care in joist selection & orientation)
Aye tell this to plumbers aswell
I love this chanel but in this case what you tried to do and what you did were not the same. This was a sprint through a long list of numbers and the only benefit I could see was which regulation to read at my convenience and try to interpret it myself. I have actually already done this and still couldn't make sense of this video.
its the plumbers and there holes for shit pipes that will collapse the building
Why drill such a large hole hole for one or two wires? A wire easily fits through a hole half that size.
I only have 1.125" drill bits. I run the super hawg drill with the quick lock extensions. That's the smallest hole the extension will fit through. Of course, being in the US, that hole size only allows 2-3 12/2 Romex to pass through. I could carry 15 sizes, but that's a waste of time. Time is money, so you standardize anything you can to keep from dragging excess tools into the job.
And then you get the cowboys coring out the joists for thier downlights! You couldn’t make it up.
Then a plumber comes along and does his own thing,
What sparks need to know is dont put cables in the same hole as my gas pipe ! Cuz they get chopped off
I’m sure that happens a lot 😂
Before anyone lifts a hammer or drill...see.if they have obvious common sense..... unfortunately such attributes are in short supply these days...
Don’t ever drill holes in your floor joists. Never.
Unfortunately all the technical information is in French not English so means nothing to those of us taught in imperial measurement even those born, breed and lived in England for 76 years, if you wish to communicate then this fails.
Well for anyone born, bred and lived in England for the last 50 years it's spot on. Viva la révolution! 😂
Useful video to summarise the regs, but WTF is with that apparently new bit at 2:00? Looks like a gibbon finished it.
Need to learn how to use centimetres 🥲
We work in millimetres
@@leemc5646 millimetres or metres, nothing in between 🙄. It’s super clever to still measure anything above 9mm in the same units, centimetres and decimetres are too hard to use.