Replacing Cracked Wooden Lintel with Concrete

Background: I'm having a new kitchen fitted and I've already replaced a window with a set of French Doors:

//www.diynot.com/forums/viewtopic.php?t=10893

Unfortunately, I've now discovered that the other window, which is 7' 10" wide, only has a single wooden lintel holding up one row of bricks. The other row appears to be held up by the uPVC window

Here's a pic of the window itself:

http://www.phykell.co.uk/diy/LargeWindowInside.jpg

Looking in a bit more detail, you can see that the wooden lintel is cracked in the middle (right where there's a knot):

http://www.phykell.co.uk/diy/WoodenLintelCrack.jpg

To the left hand side you can see a serious crack where the blockwork has pulled apart:

http://www.phykell.co.uk/diy/WindowInsideLeft.jpg

...and a closeup:

http://www.phykell.co.uk/diy/BlockCrackCloseup.jpg

Outside, the problem is obvious:

http://www.phykell.co.uk/diy/LargeWindowOutside.jpg

I reckon the cracking is due to movement as the existing lintel and the window itself, are not providing enough support. Does anyone agree with this? To fix it, I reckon I need to fit two concrete lintels, one for each side. Previously I thought that the maximum length of a 100mm x 65mm lintel was 2.4m which wouldn't be long enough to span my window, but apparently they also come in the maximum size of 2.85m:

http://www.stowellconcrete.co.uk/home/products/lintels.htm

This should do the job just fine (leaving me 8" either side).

I'd welcome any opinions on the problem and my suggested solution, thanks

If it was me I would prop the flat roof up temparory and take the lintel and blocks all out, then put in a bigger square lintel like 215mm x 215mm as it will save all that mucking about and you can render the lintel straight away. The downsize would be the lintel will be heavy unless you do it in 2 section.

You're right regarding the cracks which is caused by timber breathing expansion.

masona said:

If it was me I would prop the flat roof up temparory and take the lintel and blocks all out, then put in a bigger square lintel like 215mm x 215mm as it will save all that mucking about and you can render the lintel straight away. The downsize would be the lintel will be heavy unless you do it in 2 section.

Click to expand...

OK, I'm going to take some more plaster off the wall first of all, to find out where the bricks end and the blocks begin. I'm guessing that most of the wall is blocks and I'm hopeful for this as it will be a hell of a lot easier to cut through and remove if it is blocks. A larger lintel sounds a good idea, but I'd like to do it in 2 section due to weight as you say. Deciding on the height of the lintel really depends on if it's all blockwork. I'll find out tomorrow I guess plus I still have to find a 2.85m lintel. Perhaps my local suppliers won't do a 100mm x 65mm anyway...

This is turning out to be a *very* expensive kitchen!

I don't know the loading on the lintel but I think I understand that the roof joists are supported by the inner lintel. It doesn't look like you have enough brickwork above the inner lintel to use a 65mm one. You would be in effect putting point loads rather than a uniformly distributed load on the lintel. If the joists were parallel to the window it would be ok. A 65mm lintel to take the outer skin of bricks is also ok. It looks to me like masona is right about using a 215 high one.

I managed to find a pair of 2700mm (100mm x 70mm) that will do just fine (and get them back in a Ford Fiesta!). Apparently, my supplier couldn't do a 215mm one for some reason. It's probably just as well because, as was mentioned, the larger ones are much heavier and that would make it much more difficult for me to fit.

There's five courses of brick above the lintel above the door but above the window in question, it's blockwork *and* bricks I think. I've yet to remove the plaster and verify though but I'll bear the advice about weight in mind. One important point that I might not have made clear is that it's only a single storey extension so there's only the weight of the joists and the flat roof. If there was a second floor, I'd be using steel! Also, the joist is parallel to the lintel, so it should be fine anyway.

I must admit I hadn't looked at the pics. I remembered you saying this in the french door thread:

The wall is two bricks thick. The joists sit in the wall for one brick's thickness.

Click to expand...

so assumed the joists were going into the window wall. If the new lintel only takes the weight of the blocks/bricks then it's ok.

Finally had some time to work on this again. I've taken off a lot off the plaster/mortar to get a better look and here it is:

http://www.phykell.co.uk/diy/KitchenFrontWindowInsideBright1.jpg

You can see greater detail in this picture perhaps:

http://www.phykell.co.uk/diy/KitchenFrontWindowInsideBright2.jpg

The wooden lintel is really long and look at all the blocks above it! Ideally, I'd like to remove the wooden lintel and slot in my concrete lintel but I don't think it's going to be that easy. Luckily the roof joists are parallel to the window so there's no danger of that collapsing but those blocks look well dodgy. I reckon if I start trying to remove the lintel, they're going to fall out, together with the bricks below and above them.

Can anyone suggest the "right" way of going about this, or do I just remove whatever blockwork and bricks start to fall out, with a view to replacing them once the concrete lintel is in place?

Also, I guess I don't have to remove the entire wooden lintel as it's much longer than I would've thought, however, isn't it going to be difficult cutting it in-situ? Any recommendations for this please?

Lastly, in the roofing forum I'm asking about replacing the kitchen's flat roof and so far masona has been able to suggest a pitched roof (ideal really) but I'd need brickwork above this lintel to form an apex. I take it that if I use blockwork the concrete lintel is still easily able to take the weight or would I need steel?

There's only one way and that's take all the blocks out first; they don't look as if they are bonded together anyway. Get rid of the whole of the wooden lintel and start again. The concrete lintel will have no superimposed load other than the weight of the new blockwork so it's ok.
Masona's pitched roof is the ideal solution.

masona said:

If it was me I would prop the flat roof up temparory and take the lintel and blocks all out, then put in a bigger square lintel like 215mm x 215mm as it will save all that mucking about and you can render the lintel straight away

Click to expand...

This the way I would do it which will also take the weight of the pitch roof if needed.

Well, I've had a good look now, and will be hopefully starting this evening. The weight of the bigger lintel really makes it difficult for me to do myself and I've already bought the 2700mm x 100mm x 76mm lintels plus doing two lintels, one at a time means I can work inside and complete one - the weather has just been so bad lately, that I haven't even had chance to work on the outside! I presume when I get a roofer in to do the pitched roof, assuming that's what I go for (and I want to now!), then he can say yes or no to the lintels I've used. I'm sure they should be just fine for a pitched roof anyway, especially as there is two of them.

The blockwork is a right mess though, with almost no bonding left. I can virtually tap or even wiggle some of them out! Probably just as well I discovered the crack when I did! Some of the area is actually bricks as well. Seems like the guy must've run out of bricks and resorted to lightweight blocks (and they really are light!). Anyway, I think what I have to do is pretty clear now.

The only problem I can see now is that the bricks above the blocks will come out as well. While I can probably replace the blockwork with little problem, it's going to be tricky to replace any bricks more than a couple of rows above them because the roof joist (which is parallel to the wall) is then in the way. Perhaps this is something I'll be able to repair from the outside when the weather permits of course!

phykell said:

he can say yes or no to the lintels I've used. I'm sure they should be just fine for a pitched roof anyway, especially as there is two of them.

Click to expand...

You won't have any problem there and also the weight of the roof is spread out.