Lintel - Opening into extension

[CortinaV8]

I’ve got a 2.4m wide window that will eventually be the opening into a new extension, but am not sure what is required in the way of lintels.

Currently there is an original timber internal lintel and no external lintel at all.

Would fitting a L shaped lintel or an off the shelf catnic box lintel be ok?

My drawings show 100x225 concrete lintels for new openings, but this isn’t a new opening?

Thanks in advance for any guidance!

 

[noseall]

My drawings show

....very little? Has a structural engineer been anywhere near those drawings?

Generally, a proprietary cavity lintel would be adequate as long as it is built in, i.e built along with the masonry above, supported whilst under construction and working 'in composite' with the masonry.

Retro-fitting to existing masonry, may require a UB (steel beam), although 2.4m is a modest span.

 

[CortinaV8]

Ha! Exactly.

Not yet, I need to consult one for the ridge beam which is a condition of the building regs plans approval.

The Architect had suggested steels/calcs would needed if the wall was opened up fully (4m) but using the existing opening would be ok