Help! Joist Weakened By Deep Notch Cowboy

[@Cornz38]

I love this channel, from someone whom could only put shelves up to someone who has renovated his house (with help) its been my first port of call to see what i need to do. Thanks SB.. The best thing is that my "over engineering" trait has come in handy and i've taken steps to make sure it was done right, with the right tools and materials to make sure it only needed doing once!!!

[@SkillBuilder]

Thank you so much for your comment, it gives us the motivation to press on, especially when things are tough

[@lazylad8544]

Absolutely spot on with filling the cut out with a piece of timber and gluing it in. It must be tight to stop joist from weakening. 6mm steal plates either side with bolts job done👍👍👍

[@ReedikTuuling]

The plates only need to prevent the filler block from coming out. So 6mm is an overkill. It really is like Roger said. The top half of the joint will only be in compression

[@lazylad8544]

Belt and braces.

[@ReedikTuuling]

@@lazylad8544 The times I have seen money wasted on making something “belt and braces”. Sometimes even making the strucure worse (transfering loads to a single post/beam)

[@Farli-Gaming]

as an Aeronautical engineer i have to say you are completely correct about what you say to do with compression of the joist and by adding wood and glue into the gap as long as it is a snug fit and screw for good measure it will add strength to the joist. I would also put the some 40mm thick length of c24 down either side and coach bolt then to the Joist

[@stevehallam6495]

completely over engineering.....stick to planes pal!

[@billdavies6463]

@@stevehallam6495 What's too strong never broke... but not a way to build aircraft that have to leave the ground!

[@pn8902]

Glad you mentioned neutral axis, more trades need to learn about it. To many people its just “a hole is a hole its all the same thing”. Personally I dislike the idea of drilling through the fabric of the house so when/if I do my house I’d like to try out engineered joists with the metal webbing to pass ducting etc through, especially around the utility room where all pipes, cables and ducts would be going

[@darylsavage119]

As an electrician, please fucking do use the metal strap engineered joists. They make our and plumbers jobs so much easier, and in future changes you make will also be easier for us to do

[@pn8902]

@@darylsavage119 Agreed

[@johnmontague69]

A single 2M long (or longer if possible) pressure treated BOLT-ON using timber connectors & 3 bolts either side of the butchered out joist would do it Roger. Yes OSB sandwiched glued & screwed with the butchered out gouge tidied up & an infill would do the trick too, just a bit time consuming. These are the jobs that might need the whole joist exposed to see if you can dig a new joist into new wall pockets, slip it in, nail the old joist to the new joist so no squeeking happens after you've relayed the flooring, pack it with some slate, cement the pockets. A Dwarf wall would be ideal to work off of.

[@stevehallam6495]

i'd go with the given answer...12mm osb either side glued and screwed or nailed. Normally tho you get cocked up doing this by a run of cables drilled thru the joists.

[@petermainwaringsx]

I had to cut a joist for a trap about a meter from the end. It was about 55mm deep and I used two pieces of 50mm steel angle iron about 30 cms long and 12mm bolts to reinforce it. Even if that is not sufficient, it's too late now as the shower base is installed and thanks to your recommendation of "No More Leaks" is doing a great job. 😁 Thanks for uploading.

[@kitsophrenik]

skillbuilder is the best sub ive clicked on youtube in years. this bloke knows his stuff

[@judegraham463]

absolutely Roger. Even a layman like me can see that's a good thing to do. Not only are you adding mass, but adding strength to the weakest part of the joist/beam. Makes perfect sense.

[@smartbuildengineering]

Your structural mechanics is good Roger! The only thing I'd add is, in theory, the notch shouldn't be too close to the end as that's where shear forces are highest. In practice it rarely an issue. Sistering a joist with screwed and PU glued timber, or maybe 18mm ply is a valid approach. Can be difficult to get a tight glue line if the joist cupped, and it's the glue that does most of the work (really important to ensure the mating surfaces are clean and dust free) There are many other solutions and if it's safety critial (i.e. lots of adjacent joists have been heavily notched) then it could be worth getting a Structural Engineers input (but I would say that!). Sometimes a joist can be proven as adequate if it's oversized for the span and the notch is in a favourable position. Larger holes than intuition might suggest can be drilled, if in the right place.

[@dwalsh3469]

Shear force is constant in magnitude across a span. You can Wikipedia a bending moment / shear force diagram for a simple beam.

[@nathan87]

@@dwalsh3469 ​ The shear force distribution (as well as bending moment) depends on the loading on the beam. It's only constant for a point load. For e.g. a uniform load the shear is of highest magnitude at the ends.

[@nathan87]

Should add that the usual rule (found in several British Standards for e.g. timber construction, plumbing, electrics) is that notches go between 7% and 25%, holes between 25% and 40% of span from the ends. Although, yes, because the stresses vary with load etc I think it's more of a case of have a rule so that everybody is on the same page. If engineers know what might be done they can size joists to accommodate the worst case.

[@smartbuildengineering]

@@dwalsh3469 As nathab87 says, shear force distributions vary, and for a floor joist is not uniform.

[@gerardfarrell3135]

Yes, all good advise. General rule of thumb for site trades without grtting into the engineering/ tech jargon. No holes any lower than the top third of the joist in question. Repair approach here would be to sister the joist from both sides with a 18mm ply, a good PU glue and mechanical fixings alternating in direction. Simpson also do a bracket / fixing for around the piping going through the timber to be fixed to the timber. Works extremely well in timber I joists. Which i confess i am not the greatest fan of as an engineer and woodwork enthusiast !

[@ianscottuk]

Great, basics of beam calcs! The beam will try and sag there, so the additional material will need to be extremly tight in to help with compression. Anouther point would be if the flooring was thick enough to add structural strength above acting like a flange on an i beam.

[@colinmiles1052]

Good, basic, straightforward advice. Like it! Thanks Roger.

[@boriss.861]

Roger Perfect... I've used 18mm ply on both sides of the joist with a packer in the middle.

[@paulnutter1713]

40 years in the trade and I've seen some butchery in that time and yet I've never come across any snapped joists due to the delicate considerate touches of sparkies and plumbers. Most holes for wastes are in edges of the rooms so less weight on them maybe. Granted, most my career has been in older housing where they used proper seasoned timber unlike the shite they sell today so that definitely helps.

[@mattsan70]

couple of 6-10mm metal plates either side and bolted straight though would be my solution

[@bruce-le-smith]

came for the skills, stayed for the demented beavers lol. thanks for another great video

[@jamesbrett6518]

A demented beaver 🦫 would probably do a neater job!

[@rogerbrown9783]

Hi Roger, that information was wrong, you should only notch a joist 1/8th of it's depth to keep its structural integrity, an 8" joist should only be notched 1", a waste pipe should not be notched into a joist.

[@josoapification]

I had to do a massive feature ceiling in wedding venue in east London. It had bulkheads either side hanging from steel trusses with nowhere to hang in between a big span. When we added our joist the bulkheads started to bow down in the middle. That’s when ripped 9 inch strips of plywood onto the bulkheads. It straightened and strengthened them perfectly. Even the electrician who was a hefty bloke was walking across them .

[@we-are-electric1445]

If you make the hole square you concentrate the stress at the corners - that is where it is then likely to fail. The basic rules are in the building regs and are pretty straight forward to understand and apply but of course the biggest problem is the customer always wanting to pay the least for the job and so they end up getting a monkey to do it. Tidying up the rough cut and gluing wood to either side is probably the least worst option and obviously the easiest to do.

[@nigeld8694]

Thanks Roger, a really really useful video! It’s not always easy finding answers to questions like this on google

[@tonymcfeisty2478]

I was advised to infill the notch with a fillet of similar wood, filled out with epoxy putty, then use epoxy glue to fix two 500mm long 25mm x 6mm steel straps top and bottom of the joist on the vertical side, only using screws to hold in place while the glue sets when I needed to repair an over notched joist I uncovered on a bathroom referb. I also used the putty and fillets to fill in the numerous large holes that were also present but no longer needed. When refitting the waste I went through the centre line, as I only needed to go through 2 joists by going a couple of mm higher than centre line in one and a couple mm lower in the other I achieved a decent fall. as a bolt and braces I fitted a strap above the waste pipe to the joist where the waste passed through as I had some left over.

[@Jaaammmbbbooo]

I had about 12 joists notched out for a 40mm waste pipe. I did exactly your method before. Squared off each notch with a multi tool. Cut pieces from an old joist I had spare and glued them all in then put strapping either side of each joist. Cannot see how the joist is ever going to snap or crack. Been down ages now and it's all good!!

[@nathan87]

Yes, I've done this too; never used putty, but an infill piece secured with epoxy glue + microfibres (I always add microfibres for structural uses) seems to work very well. For shallow notches in the top of the joist I don't really see the point of adding additional strapping, for the reasons Roger explains. As long as you've glued the bottom (and the epoxy fills up the gaps like a charm) it's always in compression so you've fully reinstated the original strength.

[@sally6457]

Not exactly building control approved but will definitely make it stronger, When putting wooden plates on the side of joists I always give a good coat of waterproof pva on the mating surfaces, similar to a "Glue Lam beam". I use this method to double the height of ceiling joists in lofts before boarding out, never had a saggy ceiling yet.

[@nathan87]

this doesn't sound advisable. The tolerance of the mating surfaces for a strong PVA bond is a fraction of a mm, and unless it's clamped really evenly you're going to get a ton of gaps (clamping pulls the wood together as the glue loses moisture and shrinks). Glulam is manufactured in a controlled environment to tolerance, but I can hardly believe you get the same on site with any old joist and board.

[@paulgreene421]

Hi roger I'm wondering if your going to visit robins big build would like to see two again......

[@westwonic]

I worked in a shipyard in Finland and found on a site inspection that the piping contractor had cut a hole for a 300mm dia pipe through the neutral axis of a 750mm deep steel I beam ('plate girder') almost exactly at mid span. Luckily the new transformer it was designed to support had not been installed yet. It was quickly welded shut and repainted.

[@SkillBuilder]

Hi Nick I am not a structural engineer by any means but I have seen that done on a number of occassions and it has been fine. In fact you can buy steels that are basically a row of holes of a similar size to that and form a series of arches

[@westwonic]

@@SkillBuilder This very large fabricated plate girder was not designed to allow any adhoc site penetration, and no permit was issued to allow any site alteration. I do agree that castellated beams are often used to route small circular ducting, plumbing and cables, but in this instance this could have been catastrophic due to the very high design loads.

[@jonathanrose456]

I’ve braced to the adjoining joists in the past but, not a scenario I’ve seen in a long time

[@Nonsense62365]

In the USA hole diameter can be 1/3rd the height of the joist but always in the center because of compression like you mentioned! In the UK per your example it’s 1/4th. Most plumber in North America don’t know that. They always cut larger diameter holes then they’re supposed to and always in the wrong spot. They only know about plumbing codes not building codes! Drilling holes for electrical through 2x4 Studs and 2x4 sill plates. The holes cannot be closer than 3” on center and 1 1/2” from the edge of the 2x4’s! And you have to attach nail plates so when they attach the drywall they don’t drill through to your Romax electrical cable, PEC or copper water pipes!

[@American-In-Mykolaiv]

Great advice - logical explanation. Reminds me of some advice received more than 50 years ago: "Never send a boy to do a man's work!" Thanks!

[@badninja1971]

I worked on a job in Marble Arch. The structural 150mm RSJ had a 100mm hole gas axed out to take a waste pipe. 😂

[@freespeechisneverwrong9351]

That’s not unusual as castellated beams are used throughout the construction industry. As long as s the structural engineer was aware and agreed on the position of the hole.

[@nasserisback488]

You Plumbers love hacking floor joists 😁

[@SteveAndAlexBuild]

Jeez that’s a big old lump taken out of there 😳😳🧱👍🏽

[@garywheeley5108]

A rule of thumb for joists is width in feet ÷2 +2 so 8ft ÷2=4+2=6×2 minimum

[@JuBeYo]

The centre of the joist is only neutral at the mid span.

[@paulthomas3841]

I have had to take joint on and put new wood in

[@Vile_Entity_3545]

Glue is stronger than the wood anyway and if the block is a tight fit it will be as good as new. There are some people that have no idea of physics.

[@AngelAsylum78]

I normally sister up the joist over the longest span possible and structural timber screw it together.

[@jaccar2020]

repair solution makes complete sense

[@kendodd8734]

Still can’t understand why mf ceilings (which r common place in commercial builds) r not used more often in domestic builds they nullify so many problems u get from traditional builds u get a perfectly flat level ceiling with a variable void above to allow for all services which r easily accessible in future in case there’s problems there’s also better thermal properties and fire protection and the best part is noise reduction from the ceiling to room below there a win win win for me but a bit mite of an expense in outlay for materials

[@michaelfraser5723]

LUCKY GEEZER HAS SOME THICK OAK FLOOR BOARDS

[@olgajoachimosmundsen4647]

Roger; does notching and cutting holes in steel have the same laws of physics as wood, or is it different as the steel is more uniform in it's atomic structure? I like to think of wood as spagetti that is glued togethed. But what would steel be? Also your argument with putting in a piece of wood to support the beam; is your argument that the lack of ability to take compression will lead to greater forces of stretching that could otherwise have been taken up by having greater ability to take compression?

[@Wjracer106]

The bit you peice back in you should cut the same shape as a Stanley blade

[@manxman8008]

Good tips

[@SkillBuilder]

Glad it was helpful!

[@billdavies6463]

I get the point of reinforcing the joist, but 'tidying up' just removes more material. In metals, sharp corners are stress raisers and should be avoided. Would ordinary wood or plywood be stiffer than OSB?

[@therealdojj]

The weight of the joist is going to be at the bottom where it wants to snap It's the same as why you should always put the reinforcement metal bars at the bottom of a concrete lintel Roger has explained it very very simply but the engineering behind it really does need a practical demonstration As for osb, from what I'm told it's stiffer and stronger than just a normal board And you are right about radiused edges on metal, when I was building engines it was always the done thing to stress relive the edges

[@chriskane9230]

OSB is stronger than both, This is why an I beam Joist will have OSB as the upright in the design.

[@johnmontague69]

Correct way to fix it is to put in a new pressure treated joist. However, you don't need to take out the old joist you can dig out new wall pockets slip in the new joist next to the old 1, jam it up with slate nail it to the old joist, cement the wall pockets, relay the flooring. Depending on how much room or space you have, you might not be able to put in whole new length of timber because of other services. This where the 2nd choice always wins for me because it's fast and structurally just as good as whole new joist. A Bolt-On of 2M long using 3 staggered bolts with timber connectors (M12's) either side of the weakened joist. Thats all it needs. If you can get more than a 2M bolt-on into the space then that's even better, just add extra bolts and timber connectors if needed to fix the new timber flat against the old timber. There are several ways to fix this problem, the bolt on way with pressure treated timber with M12 bolts timber connectors & square washers is the preferred method for quickness. If I seen this in my own house I'd rip it out and replace it with a whole new joist. Taking away that 1 old timber joist guarantees that your new joist is not going to be affected by wood lice & anything else that's nesting on a microbial size. If you can expose the whole joist system and the joists are over 40 years, spray the whole area with insecticide & pesticides before rallying the floorboards, this guarantees 25 years of insurance that nothing will hatch and start eating away at the timbers. Yeah.. especially PLUMBER'S lol.

[@MrB3ngy]

@@chriskane9230 I’d disagree that osb is stronger than a hardwood ply, osb is used in fin joists because it’s cheaper.

[@garyfardon8841]

It's called tension Rog.

[@madcarew5168]

I Know that plumb....

[@johnmontague69]

Yeah.. the pilots neighbour is a plumber... lol 😆

[@MrB3ngy]

3/4 marine ply. Rather than osb 👍

[@tillyfoxtrotter]

agreed - I found the OSB suggestion a little odd to.

[@stevehallam6495]

@@tillyfoxtrotter engineered joists use osb as their web....plenty strong enough.

[@wthomas7955]

I had an idiot plumber do this to me one time.

[@ttfweb1]

Top notch commentary Roger. By the way, my university mascot is a beaver, as you can see from the icon. Hopefully not often demented.

[@jamesbrett6518]

🦫

[@advanced8526]

Metwood Joist Reinforcers for the WIN in this situation

[@SkillBuilder]

Thanks for that info, I didn't know about them

[@tonyholohan6756]

never heard if those before?. so i just googled it. Very clever!!

[@SloopyDog]

Somebody has been a bit brutal with that joist, I have seen so many joists treated like this. Often the joists have been cut out for cables and the boards are laying on the cables.

[@loc4725]

Water pipes, and it's not until a few years later that someone notices a slow leak from under the floor.

[@lmilne4859]

Sounds good to me will make it nice and solid.

[@Graham_Langley]

While investigating a shower leak in a new loft conversion at a neighbour's house I found the builders had done a similar hack job on the bottom of a new joist to get the waste to where it needed to go. Told them it needed dealing with but the 'builders' had disappeared and I suspect it remains unfixed. The shower leak was down to the trap not seating properly due to a lump on the ceramic. Instead of removing it they'd smeared around the trap with silicone after fitting it.

[@Graham_Langley]

@Flip The Pickle Because they were a pair of cowboys.

[@huyongquan6554]

The industriy is a joke. hole and notch shall be seperate within their own zone, in reality there all appears together all through under the floorboard. cable laid in notch cause senario cable within 50mm depth from up so need 522.6.204 mechanical protection otherwise not apply BS 7671. I think who edit BS standard or Building Regulartion knew that but still self blind them.

[@nathan87]

You're absolutely right, these rules aren't followed enough, and it's super annoying. With regard to zones for notches and holes I think there are two causal factors here. Firstly, buildings are overdesigned, partly because you've got to accommodate things like joists being changed, partly because engineers know that tradespeople won't always obey the rules. But this just leads to tradespeople seeing that breaking the rules is fine and they just keep doing it. Secondly, it's just the quickest and cheapest thing to do. Homeowners don't want to pay too much/have too much disturbance and tradespeople want to get the job done and get out of there. Laying cables in notches where you can screw straight through them is frankly inexcusable. But again it's time consuming and expensive to repair the notches, so I kind of understand why it happens.

[@acespark1]

All electricians the correct information is in your onsite guide 7.3, plumbers ask the electrician to show you the onsite guide. Both of you could ask the joiner 🤡🐔

[@sally6457]

They do ask joiners, then smash it out anyway. Most plumbers and sparks I've worked with should be banned from owning power saws! 😉

[@Chequr_Prostate]

Can’t ask the Joiner he only speaks Polish….

[@sally6457]

@@Chequr_Prostate hahahaha 😂

[@12000gp]

Why would a sparks be cutting a hole like that? Plumbers are the ones to worry about

[@Itchytriggerfinga]

A qualified plumber wouldn’t do that. Bathroom fitters who are often not will.

[@whitefields5595]

Would have been good to explain it to the pilot in terms of a plane’s wing deflecting the main spar.

[@Graham_Langley]

There's a lot more going on on an aircraft. There's a section on torsion in J E Gordon's 'Structures - or Why Things Don't Fall Down' about the Fokker D8s where stiffening one of the wing spars made a particular situation worse. Counter-intuitively the solution was to weaken it. It's a good read and there's an easily-found PDF online.

[@DerekTJ]

A dutchman piece

[@TheSudsy]

1:05 Not sure my missus has been near that house ...

[@KurtMGibbs]

Demented beaver...haha!

[@kieronkehoe]

Fuckin bwrilliant Roger. I use forstener bits for holes, which i prefer, but decent notches are great too.

[@gregmulligan2878]

I hate demented beavers. They do terrible work

[@LabRat6619]

The days of boxed in wastes seem to be over, now its all hacked out the timbers. So much for fashion's.

[@stephendendy8376]

Why do so many know it alls watch your content a feel they have to add their patter

[@SkillBuilder]

We love comments, there is wisdom in crowds

[@stevehallam6495]

For anyone saying bolt another joist to that one if you are fitting another full joist next to it the notched one becomes irrelevant structurally, why bother with the ball ache of bolting? Yet another case of over cooking and over engineering in building. Just beef it with some osb or ply rips and move on.