Using a 260mm cavity lintel over a 300mm wall space

[fourteen0407]

Hi all,

Just want to check something.

Im building extension wall which is the standard makeup of 100mm block 100mm cavity 100mm brick.

S0 300mm in total.

so the builder has got to the point where he's made the space for one door and two windows and has bought 3 cavity lintels.

Lenght is fine, but The width of each lintel is 260mm' so 40mm less than wall width.
But the builder has insisted that it ok to use still and at the intern does not have to sit it and cover the entire width of the wall.

Is he correct.

these are lintels that will.go over the 1 door and two windows on an external wall.

Thanks

Margaret

 

[^woody^]

No, they will flex. He needs to buy a suitable lintel for the 100mm cavity.

Possibly bought it because it's cheaper.

 

[fourteen0407]

Possibly as he supplied all materials.

But he has told me now he has already fitted them and added 3 courses of brick ontop.

So is ot worth ripping it all out or just leave them in.

There will be 3 courses of brick ontop and then small 2m long rafters sitting on top of wall

 

[^woody^]

It's your house, you are paying him, the idea is that he does what you tell him not what he likes, and the expectation is that he does things correctly. You'll deal with future problems not the builder, he'll be long gone.

Tell the building inspector see what he says, or ask the lintel maker rep what he thinks.

 

[fourteen0407]

Thankyou for your advice,
I did contact the building inspector but he replied "its not something they cam advise on.

and the shop where I bought the lintel has just said he does not know as he just sells them.

The thing is now I've been to the property and the builder has fitted all 3 lintels, two over the windows and one over the door space.

and then added on top the three courses of brick alll down the wall which is 11 m long.

So un doing that will take a lot of work and expense.

But the builder who is to be fair a reputable builder in the area has said again that you will be fine.

can anyone please advise whether it's great ripping out all the bricks and taking out all lintels.

like I said there will only be 3 to 4 courses on top of these lintels and then one roof end will come down and sit on top

 

[tony1851]

The builder is correct. The overhang of each skin will be 20mm, which is acceptable in structural terms (the code for brickwork design allows an overhang of up to 1/3 the thickness of a skin).

Independent from that is the depth of the lintel - this, and the span, will dictate its load-carrying capacity. Three or four courses of brickwork + a roof is not much - the lintels will be fine.

 

[freddiemercurystwin]

The builder is correct. The overhang of each skin will be 20mm, which is acceptable in structural terms (the code for brickwork design allows an overhang of up to 1/3 the thickness of a skin).

Independent from that is the depth of the lintel - this, and the span, will dictate its load-carrying capacity. Three or four courses of brickwork + a roof is not much - the lintels will be fine.

I'll bet my leotard the builder in fact doesn't know any of that and just wanted to save a few quid. The fact that he may inadvertently be right is a happy accident.

 

[fourteen0407]

Lol true. Thankyou all for your help and assistance because this has worried me all day.

I've really hoping that the 40 mm short in total wouldn't mean that we would have to rip it all out and then cause delay again.

 

[^woody^]

The builder is correct. The overhang of each skin will be 20mm, which is acceptable in structural terms (the code for brickwork design allows an overhang of up to 1/3 the thickness of a skin).

Independent from that is the depth of the lintel - this, and the span, will dictate its load-carrying capacity. Three or four courses of brickwork + a roof is not much - the lintels will be fine.

Why do the manufacturers make several sized lintels for different cavity wall thicknesses, if by your reckoning you can use narrower lintels in wider walls?

IG seem to disagree with your assertion.

I would suggest that you are wrong by the assumption that the overhang, whilst it may be permissible as an overhang of one leaf, it does not mean that the lintel is acceptable in a wider wall. The way these lintels work means that the position of it within the cavity and the position of the upstand is more crucial for performance. In fact, IG state

• Lintel should be centred in the cavity and the distance between lintel up-stand within the cavity and masonry (A) must not exceed 10mm

So by that, the lintel is not acceptable.

 

[tony1851]

More 'spokes in wheels' !

I don't doubt what you say, but we're not looking at a multi-story block of flats but 3 or 4 course of brick and a roof. Presumably it will be set and hardened by now, so it won't be going anywhere.

And ultimately what would the OP gain by asking the builder to take off a roof, 3 or 4 courses of brick and scrap three perfectly serviceable lintels? Probably a skimped replacement job by a disgruntled builder and bad feeling all round.
We all have to live on Planet Earth.

 

[^woody^]

The way the leafs are further from the centre mean there is more rotational load on the tray and so more prone to flex and any movement could cause the panel above the area to crack - movement that a suitable lintel would accomodate. Whether it might be OK does not come in to it.

Its a massive risk and one that a client should not have to bear, when the correct lintel should have been fitted in the first place. If it does crack the builder is long gone and not interested, and the OP is paying for something that is wrong and that's not what they should be paying for.

 

[fourteen0407]

Thanks all for your responses,
I'm confused now lol

Is it fine to carry on, as now builders have fully laid 3 courses above lintel of block and bricks.

Then eventually the rafters from existing roof will come down sit ontop of this part of new wall, about 30 joyces in total along 11m wall. 1st 6 joyst will be no more than 2m in lenght. 44x122 @400 c/c then last 20 will be around 5.8m in lenfgt.

 

[tony1851]

Get out a step ladder and have a look down the line of brickwork: does it noticeably sag in the middle of the widest opening?

 

[freddiemercurystwin]

Does it sag a bit? I thought you said

the lintels will be fine.

 

[wessex101]

And ultimately what would the OP gain by asking the builder to take off a roof, 3 or 4 courses of brick and scrap three perfectly serviceable lintels? Probably a skimped replacement job by a disgruntled builder and bad feeling all round.

So the builder fooks up but cracks on regardless but its best not to say anything in case you hurt his feelings?

I usually take the view that if he can make such a basic mistake then his competence is called in to question and everything else he has done is suspect and I would be looking at everything very closely. I certainly would not accept it on one of my jobs.

As for the lintels, the simplest solution is find out the manufacturer, Catnic, IG, Keystone etc. and then phone up their technical department and ask them. I've always found them to be very helpful.