Rotten lintel above bifolds

[Lizs2]

https://ibb.co/YpsM5hV
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Hi,

We’ve just had some bifolds fitted into a previous window opening. The width wasn’t altered just the lower bricks removed and a SE advised me that the existing brick arch was sufficient as the load was transferred down the walls so we didn’t need a new lintel (casual convo whilst he was here for another job)…

Door has now been fitted and we’ve since removed some coving which brought down plaster revealing an internal wooden lintel which is rotting on one side. Probably should have done this prior to the door going in but you live and learn, there were no obvious signs of any issues.
The wall is two bricks thick with no cavity. Above it is a window that appears to just be on the outside skin of bricks.

I’ve tried to attach some photos showing it.

I’m just wondering if anyone knows how much support this beam is likely to be providing and how urgent this is to replace?
it is likely to be a big and expensive job?

thanks
Liz

 

[^woody^]

Now you've exposed it all, I'd say you're better off replacing it sooner rather than later.

There's support from the arch, so as lintel replacements go, that's relatively easy. But care needs to be taken in the detailing of the new install so that no moisture gets across from the outer half of the wall to the inner - as that's clearly what's been going on for years.

How expensive it is will depend on your local quotes.

 

[Lizs2]

There’s a bathroom above this end so it’s possible it was a leak from there also, doesn’t feel damp now and a new bathroom was put in a couple of years ago by previous owners so hoping that’s sorted. It’s also had new boards on the top of the doors so don’t think it’ll be an ongoing issue. Can it be done without removing the doors do you think?
Was hoping to get it all plastered before Christmas so going to be an eyesore till we can get someone in.

 

[^woody^]

There’s a bathroom above this end so it’s possible it was a leak from there also,

Possible yes, but unlikely unless you have had a leak for decades and not noticed it. It looks either like old dry wet rot or even more recent dry rot

With solid walls, any water entering from driven rain goes inwards and downwards. That frame is set quite far forward so there is a high risk of water getting behind it from above and into the wall that you will form when changing that lintel below that arch, and if so you will see it as damp on the nice new plasterwork above the frame.