Why Has This Lintel Cracked? 

I'm an engineer and we have a saying at work "if it looks right then it probably is". That lintel doesn't look right. It's the wrong product for the job.

I am not a builder just a basic DIYer but I am really enjoying these short videos on problem investigations. Keep them coming please.

For a non-Engineer you explained it very well. When doing stress calculations on a beam like this the inherent 'strength' of the beam determines the load it can carry. By straining the metal bar and letting concrete set around it, the inherent strength of the beam is increased, It is pre-loaded (= pre-stressed). It contains energy, strain energy. This can be compared to your van. Its static weight that pre-load the spring with twisting energy in the spring. When you go over a pothole the wheel is pushed downwards by this release of strain energy stored in the spring. Without this the van would lurch into the pot hole. Same thing with continuous railway lines. These are stretched and welded at the same time. When the sun heats them up the stored tensile strain energy absorbs the energy of thermal expansion and so they don't buckle. Strain energy stored in toughened glass makes it shatter into small pieces. The upwards curve of the lintel is encouraged because concrete is very strong in compression. For the beam to sag it has to go through the mid-position which is resisted by the compressive strength of the concrete on the upper surface. Building the lintel into 'wet' brickwork adds to the compressive resistance on the upper surface. With the upward bend the additional bricks would all have to compress for the beam to pass the mid-point. Built in 'dry' then there is a built-in fault line above the lintel that can move a bit more than if it were all done wet and set at the same time. There is however an ultimate load in all of this. The weight of bricks above will ultimately exceeds the benefit of their compressive strength, its going to sag.

Well said “you never stop learning”, unfortunately some individuals never start. 😂

Hi Roger, love the video. I have some experience with this type of situation. One thing that's often overlooked when designing or choosing a beam is how it will deflect (bend) when underload (installed). When doing a job like this its not just a case of assessing the beams capacity to take the load (dead and imposed loads) but also how much it will bend and sag over time as the load is applied. There are British standards that are used to assess beam deflection and if it will cause cracking to plaster or any final surface finishes. An added complication in this case is when lintels are installed in this scenario there is likely to be a small gap above the lintel and the brickwork above it. Meaning over time the brickwork will sag and start to fully bear on the lintel and cause it to deflect. If the beam deflection hasn't been taken into account when selecting lintel size then you will see a crack. This link gives a guide for steel, principles are very similar: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-brC9JEKqV7M.html

Bang on Roger, “Wrong Lintel, wrong guys”, succinct & straight to the heart of the matter. Should have been steels, no argument.

In 35 years I’ve never heard of a plank lintel 😳. The fact that there is a full pike/ gable above that room means that wall is load bearing. My guess is that the left hand one is in correctly and the right hand side is maybe upside down? Meaning the pre stressed camber is pushing down instead of up . On openings that big steels every time 🧱🤙🏽💪🏽

The change of loading onto the central pier to support the gable wall may mean the foundation are not sufficient for the increased loading. When it was a full length wall the loadings would have been spread evenly along the foundations now they are concentrated onto the lintel bearing points and then through the piers to the foundations, point loading.

I used 150mm for a much shorter opening non-load-bearing wall. 75mm doesn't look reliable enough for me 😅

Spot on Roger, as soon as I saw that, I could see that the incorrect lintle was used.. Steel would be the way to go..

Did he have a structural engineer's calculation? Were building control involved at all?

Excellent roger..

Didn't even realise you could get those lintels in that length. It won't even support its own weight over that span. I wouldn't be surprised if the bricks above are supporting themselves and the cracks have occurred where the lintel has sagged away from them under its own weight

That scarf is certainly 'entertaining' Roger! 👍😎

Never seen a "beam " like that before. Only time I've seen a flat lintel is above a short apan like a window opening. There's no strength in that. That added wih probable inverted installation could account for the drop or sag. Get the builders back in. Give them cups of tea and plenty water for their horses.

I think when you build it as one the cement and brickwork above will set as one solid object to the lintel. When you try to introduce a new lintel under neath old brickwork it just won’t form as one solid object. I reckon they might have the Lintel upside down. Having followed many structural drawings I’ve never installed a lintel of 65mm (assuming it’s uk) with that span. It would normally be a a UB or a double UB bolted together.

You're right about the compression of concrete lintel. They have to be built in wet so the weight of the bricks pushes down against the upward force of the rods. The opposite effect is with those thin metal lintels you have to support them with timber until they go off.

Roger your channel is one of the best. I don’t comment on these types of platforms often, but I want to offer that this may be an interior wall, (ie not likey but possible for sure, we cannot see the layout but I may be wrong and it is indeed under a gable- the drawing is not a shop drawing nor blueprint) and I’m wondering if it’s a combination of poorly installed finishes in conjunction with the issues that you already mentioned in the video. We have that problem with drywall stress cracks at corner bead when it’s not installed correctly and when there’s movement in the walls. If this is the case, the cracking would’ve been caused after the finishes (ie in my country, drywall/plaster, trims, paint) installation by any additional work done above the are or by dynamic loads above the lintels. In addition to poor design, the execution of finish installation can contribute (though not “cause”) these types of issues. Thanks for all you do! Kudos!

If there is gable end brickwork above that would be classed as a load bearing wall, even it wasn't supporting joists or purlins, it is supporting the weight of the masonry above!

Those 65mm lintels should have 2 courses of Engineering bricks above with ex-met reinforcement in the bed joints, built in one go as you said Rog so in effect it becomes a 225mm deep solid unit

You can see there is one acrow prop supporting the middle of the lintel before it's plastered in. That would suggest to me that maybe instead of fitting the lintel and installing brick work above, or dry packing with mortar they may have tried to wind the beam up to the underside of the existing brickwork. If I were installing a lintel or a steel beam I would form a pocket or shoulder using a padstone (are there any padstones?) and sit the ends of the beam/lintel on that. Sometimes you can't do it that first and might need to build the padstone up to the bottom of lintel/beam, in which case there should be a prop at one or both ends while the mortar is setting.

You are correct Roger about the courses of brickwork above the lintel being required in order to form an arching effect. The manufacture normally stipulates the minimum number of courses required for the sectional size of lintel, this could be something like 3,5 or 7 courses. Your are meant to lay the lintels with the rough side up and just like rendering you should give your brickwork and lintel a wet down first with something like a garden pump up pesticide sprayer to control the suction much like in rendering with a scratch coat or priming. Also best to pack in structural non shrink grout between the existing brickwork and lintels. Think of the brickwork and lintel combination being like the section size of timber, the deeper the beam of the brickwork and lintel the greater it can span. It acts much like a floor joists versus a ceiling joist or a common rafter vs a hip rafter. Also the brickwork either side of the lintel matters, en castre is the engineering term if I am not mistaken, this resists the deflection/bending moment of the beam.

it was nice to hear you on BBC radio 2 yesterday!

I’ve recently removed a load bearing wall to form a open kitchen diner, used a RSJ and no cracking at all.

Even if the beam is correct for the span it should never have an acrow jacking it up in the centre. If this needs to be done to squeeze the mortar between the lintel and bricks above it should be done at each end. This takes out any bowing which may take place once the mortar is set and the props removed. It looks in the pics that the lintel has settled in the middle causing the cracking and can probably be packed and repointed assuming the lintel is correct for the span and there’s no underlying structural issues.

If its a fair face or fire spec lintel they have a top and bottom and are usually marked, but rule of thumb is to position the reinforced steel rods towards the bottom away from load thus eliminating sag.

Usually in a prestressed lintel the top of the beam is the rough bit. Also the stressed rebar would be in the bottom of the concrete with about 50mm of cover. Concrete is strong in compression and weak in tension. Hence the bottom of the beam would be in tension if the load was great and the rebar here was not prestressed. In this way you can get away with a smaller beam. But at 75mm you could only have rebar right down the middle so prestressing would not have as significant effect

The bearings on those lintels look rubbish, it honestly looks terrible. Normally building control want a minimum of 150mm bearing if a lintel is retro fitted. Also on some sort of Padstone. That looked like a load of cement just parged in. Also like Roger said, it would have been steels not a shite concrete lintel.

I’m surprised that got past the Building Control inspector. It wouldn’t have got passed by my local Council.

Bringing new build quality to old build property.

I put in a concrete lintel just like that. About same length. But mine was 150mm tall and only held up 5-6 course of brick which the rafters didn't sit on anyway. I'm not sure if I set it in correctly but hopefully over did it on inherent strength side.

Looking at the picture it looks like it was a garage that's been converted. Hence the roof above. Either Way you can only remove two thirds of a supporting wall . This looks like more has been removed. The cracking has occurred because the builder has pushed the lintel up in the middle with an acro prop when bedding it in . Hence it's dropped back to its neutral state . Just cut out and repoint with a finger trowel.

I believe the interlocking of the bricks above the linetel is called the cordobelling effect(bricks lock together preventing collapse.

Marginal depth pads atop that pillar as well.

It would be nice to see the brick work above to see if there is any cracks

👍👍👍 Thanks.

Where is the building inspector. They have to be involved on structural work. They would not have allowed a prestressed lintol in that situation surely.

Composite Vs non-composite are the 2 types. One needs bricks above it, the other can take direct load.

Roger, what's going on with the desk and multi-screens?...you look like you're presenting Sky news! Kidding, mate. Love every bit of your content.

Shows how important it is to now protect unsuspecting customers and regulate the industry to prevent any upstart calling themselves a builder imo.

A 9" x 6" concrete lintel for that span is a must, a single course lintel is bound to sag

The wall below the eaves/ceiling level should definitely be described as load bearing if there is a brick wall above. All lintels of this type with brickwork above must be designed for the weight of a triangular brickwork area directly above in accordance with the relevant standards (which assumes the brickwork above the triangle will arch and support itself). In this case the depth of brickwork above the lintels at either end may not be sufficient to conform with the relevant standard (i.e. insufficient to arch properly above the nominal triangle) due to the gable shape and a more liberal loading should be adopted for the lintel design.

On my extension( single story) I used a steel that accomodated the block and brick over the door and window.Very little load on it but under building notice it should and would be capable in the future of supporting a second storey above if that was ever done not that I will but in the future someone may.Much like the footings I built it on.Able to support another storey easily.To be fair UK building regs are as good if not better than any in the world structually.I prefer to over engineer any job than under engineer.

Like someone said its not the UK? It would be steels with UK regs and that pillar looks ropey too, would probably be a steel too in UK. As it stands it probably won't crack more so just fill it if its definitely got no loading but I'd want a structural engineer to have a look.

Ugh get rsj's in there ASAP!

0:43 you can see the electrical panel - that looks like a USA panel, that might explain some of the points and issues and techniques used.

As you said Roger prestressed lintels are supposed to have 6 courses over and anything over a metre is supposed to have a 150mm bearing that looks like 100mm also there's often a way up to them too I took one out of the garage door opening on a townhouse Ashford that had a crack in the middle when we got it out there was an arrow on the front pointing down, it had been layed upside down 9" deep with one rebar in at the bottom

So if it has a set of bricks on the top, presumably as they are rigidly connected, they become part of the beam and are in compression? Hence why you can get away with the plank sizing.

Easier to install upside-down since any bow won't hit the bricks above it!

There’s not a lot of bearing by the looks of it either roger, can’t believe that was knocked out without a strong boy in sight 😬😬

You look like a Radio 2 presenter sitting there all wired up 😂

I think pretty much everything is covered in the comments. Brickwork really needs to be built over them as you go and fully propped until it has cured. There is plenty of room to use 150mm lintels or steels. I certainly wouldn't consider using such a lintel on this span retrospectively.

Issues like this is why we use structural engineers. Above our pay grade to understand why it's not enough to take the load 😅

The span is way too long for any notable load for a prestressed concrete lintel of that depth to provide structural support. I’d never design one for a span over about 1.6/1.8m. Roger, did you ask the guy to send the structural calculations? Does he have any?

Don’t stress out too much as it is that tiny pilar in the middle that failed 😅

looks like the lintel is not sitting on enough brick! Not a reason for it to crack though. Can only see cracking in the plaster work! Could the lintel be Ok behind the plaster?

The point of building the brickwork on top of the concrete lintel is that the bricks "hold the end of the lintels down" and also the mortar ties lintel and the bricks together. If you just squeeze the lintel under the existing brickwork you support the ends of the lintel on the bricks at the ends and the lintel doesn't really support anything (the bricks will "float" above it, even if there is no gap) - sooner or later you get this "triangle" above it because those are the bricks it was supposed to support. In this case I assume the lintel was soo long (and maybe upside down) and sagged on its own weight even without the bricks pushing down on it. Assuming the lintel could have supported the bricks above - if you laid the bricks on top of the lintel, they would have bent the lintel a little, but because everything would have "sagged together" you don't get a crack anywhere.

Lintel not strong enough or packed properly under brickwork above ?

I'm not sure why they didn't use steel box lintels...you can get them made to just about any dimensions and you can offer them to the upper coarse because you're allowed to pad the ends. 🤷‍♂

from what I can tell from the pics i would say it is load bearing, but would need to see more to say for sure. but either way you need to get somebody to look at it properly and im guessing rip it all out an put steels in.

Simple rule in sizing: If it looks right it is right and vice versa

continuous wall ? how is that not load bearing?

You could maybe educate me Roger, but thats a hell of a span for a 75MM lintel init?, just asking

I’m not a builder but I would want a structural engineer to see that before any works done , I would hazard a guess this was done let’s say on the cheap.

How’s that been passed by building control ?

What did you mean by "equalised"?

? how did building control pass this? Bearing is too short and as stated should be a steel or load bearing lintel.

Imagine that the pre stressed lintel was installed upside down? The bow pointing downward???

Should have put a steel in on pad stones job done

It seems a very odd choice, I would assume the length would make a steel the optimum choice. I tend to assume when space isn't a premium you don't want it to feel marginal.

First thing is this sort of structural work needs building reg's approval and if you do that you'll need structural calculations for the lintels. A structural engineer would specify a steel for this job, single course pre-stressed concrete lintels are generally just for small spans and standard/light loads. It really is worth the extra expense of doing it with BR approval as not only will you sleep easier and have no problems but when you come to sell the house you can run into big legal issues with the solicitor costing you much more than the few hundred it would have cost you to do it properly.

Did they go through building control? Did they use an engineers design? Or was this the builders idea? I suspect the latter. Which may cause an issue when they try to sell the place. Any search by a surveyor will show the work was never signed off and it'll need retro inspection. If they went through building control and an engineer, the install must be wrong. Maybe it wasn't packed well. But my feeling is that they should have used RSJ's. I cant see how it's a non load bearing wall with that gable above. And that supporting pier don't look sufficient, it should maybe have been a steel post bolted to the RSJ's.

A non load bearing wall would terminate within the floor/ceiling joist

thats not in the uk looks like south africa

Not surprised that has cracked. All the loading from the gable end brickwork is now transferred through that tiny central column into the foundation. The two side walls will be under increased stress too. I'll bet they didn't check that whatever was underneath was capable of dealing with the increased load. In fact I'd wager that whichever shaven monkeys did the work didn't check anything much.

The beam is upside down 💯 the force is wanting to push down centrally

Do the concrete lintels not have a top and bottom? How can the manufacturers determine in which direction they will bow? Is it by placing the rods offset within the concrete? 🤔

Surely a gable end wall is a load? Too much flex on a lintel that thickness with the span. When built in from the beginning the cement bonds to the lintel making it far stronger …

That’s horrific that they used 75mm concrete lintel instead of RSG, that was to cut cost corners.🤠

The reason prestressed lintels tend to arch upwards should be because stressed reinforcement is placed below centre and the off-set results in an upward bending tendency. Could it be possible that they have installed this lintel upside down? That would greatly reduce the strength of the lintel, not necessarily catastrophically if it is not heavily loaded, but it could account for the cracking. As an ex- structural engineer, albeit with limited experience, that was my first thought.

This is a mystery Roger, there is an inside on this side of the wall and an outside of the wall. So, basically, there is no brick work in the middle of this home. Is there? Curious, because you are awesome, but maybe the pictures are just misleading.

when I did building work with concrete lintels or even steels in this way I would tress the lintels by hammering wedges between the centre brick and lintel or beams so it took the load, basically taking the slack out of the lintel or beam

Obviously does not have Building Control consent either ! If it collapses someone will be up in front of the judge for manslaughter charges. I can’t emphasise the need to get professional help with building alterations

Just a question (driffting somewhat) What became of Roger and Rob Clevett ??, thought they were big pals.

I can't see how that is not load bearing, looks like they need to prop asap and get some steels in there

I do not like the look of any of that, it does not look safe. Have they plastered directly onto the concrete lintel? the same coving is visible in the before and after. At 1:18 The original plaster on the brick seems to be flush with the side of the lintel.

I would have got a structural engineer to look at the job to calculate the opening for the correct lintel of steel.

Hi… we have a cracked lintel in an old Victorian house. I can send you pictures. We have insurance coming to look at it but thought would we would as your advice.

they put the pre stressed side arc facing down

This hasn't been seen by building control or a structural engineer, it is not safe, you need to get some props under this soon as possible, is the concrete floor beneath the central peer capable of holding the weight.

😂 gable end is not load bearing? I’d love to see him lift it down and pop it back up if there’s no weight in it 😂 Not like brick:block have any weight to them or the roof tied in would add any additional pressure. I’m with Rodger a steel would have been a better job, plus as we all know the fire retardant paint makes the steel 10 times stronger again 👌🏼👌🏼

Those 75mm precast lintels are non load bearing!!!!

I think he needs to get a structural engineer in for a look in case it is load bearing. Not convinced he's clear enough about that. Would have thought best practice would be two steels, and depending on the load possibly a column.

I'm no builder but that sht don't look safe I'd go and get some acros supports sharpish as that sht looks like it could drop any time soon.

Roof no load , haha

Just a guess. Could have been installed upside down, Then the acro has forced the lintel straight and now removed is bowing down again.

Should of had the pillar removed all together and had a massive steel end to end

Old brickwork is always loose, so it was going to fail,

One rule of thumb for rc is beam depth in inches = beam span in feet. That beam may have been installed on its side….

these concrete lintels are OK for a single door opening but the span of that opening is far too much for the capacity of the lintel and it has just over deflected. The builder has not consulted a structural engineer and just taken a guess at using that lintel. I suspect that he has not made a building regulation submission. The lintel is carrying load - the masonry above - so it IS load bearing. I am wondering if he thinks it is not load bearing that he doesn't need to make a build regs submission. As you rightly suggest Roger there should be steel beams going in for that span.