Concrete Lintel

[Watshot]

Hi, I'm building a porch across this opening and want to change the wooden lintel. This is so I can use it above the new window in the porch as it has done all of it's major movement in the last fifty years or so, and therefore wont mess with the new stonework. And secondly, because if left where it is, this will become an internal plastered wall, and any slight movement in the wood may cause cracking to the plaster.



The open span is 1.5 metres, so would a 1.8m (100 x 65) concrete lintel be right to carry the stonework above? There's no other load other than the outer leaf stone wall above. Existing wood lintel is about 150mm square.

I could of course narrow the opening, but at the moment I'm thinking internal door with sidelights to maximise the light through the hallway, and I could still do that afterwards anyway if the lintel was within spec for the total width. Hopefully it's a straightforward swap rather than trying to get hold of a structural engineer at Easter!

Many thanks.

 

[^woody^]

Yes you can do that. A waste of time and a lot of messing about for no gain, but yes if that's what you want.

 

[Watshot]

Thanks Woody.

I gain a decent bit of timber that won’t mess up my new stonework and matches the rest of the property. Not something that can be easily, or cheaply, bought. The effort is worthwhile, sometimes it’s not just about taking the easy option....

Cheers.

 

[Ian H]

There's a 140mm concrete lintel that would fill your gap better.

 

[^woody^]

That oak beam is still and will always change seasonally and like that existing stone work has cracked, so will any new porch stonework.

The time spent messing about removing it, and then re-using it only for it to perform exactly the same (ie still vary seasonally) then you could if you wanted get a new one which will perform exactly the same. Or achieve the same effect with a normal lintel and piece of oak.

Bear in mind that random stone is much more difficult to prop up to remove it, and it's not standard load anyway due to it being near the side of the gable - a lot of diagonal load there.

But yes if it's worth the effort then yes a 6' concrete lintel will do, but may be better with two put in on edge if that gap is 100 deep, and it's just the outer leaf.

 

[Watshot]

Just to clarify; the stonework isn't cracked. There's a dark vein running through it.

As the beam moves "seasonally", it will of course crack away from any pointing. Which is why I said in my first post that I would rather not plaster over it once it's internal. One of the reasons for removing it. A decent sealant will cope with any pointing cracks around the beam perimeter once it's built into the new wall.

The fifty plus year old beam will not move to the extent that it would dislodge or crack any new stonework. Which is the main advantage. Unlike this green oak lintel that was removed and replaced from the rear extension having ended up like this:

Twisted in two dimensions.

As my question only related to the suitable performance of a replacement concrete lintel and not whether my time was well spent, it's something of a moot point now:

As Ian said, a 140 would have been better, but I couldn't get one on a bank holiday so went with two 65's so that I could finish the job.

 

[kingandy2nd]

That was quick!

Tidy job, although I left my props in while the mortar dried.