Lintel Bearing Width

[Henners]

I've a bathroom window on the first floor of a gable-end wall (non-loadbearing). Window is 1.200m * 0.9m.

I want to install a second window in the bathroom. So I pared back the plaster around the current window to see how far the lintel bearing extended.

The lintel supports about 5ft of brick and block work.
This a 20 year old house. Bought from new from a reputable local builder. No apparent problems - no cracking around window frame

The current lintel seems to be mounted on bearings of about 15mm. I'm guessing the equivalent of a 1.25metre Catnic 5/100 is installed.

Should I be concerned? If I should, what remedies might I have.

 

[noseall]

15mm seems awfully lean. are you sure its only 15mm?
by the way does this new window face the neighbours?

 

[Henners]

Yes, it's 15mm.
Drilled a small masonory bit @ 150mm then 100mm without hitting anything. so thought I'd pare back the plaster over the lip of the lintel till I found where it ended.

Yes the new window faces the gable end of the neighbours wall, so I'm prepared to submit building notice to the local council.

 

[noseall]

how close is the neighbours wall to yours?
15mm?. how far in did you drill? you may only hit metal if you drill deeper than 125mm.

 

[anobium]

Any type of lintol should have a minimum bearing of 100mm at both ends.
Are you really sure its only 15mm?
This contravenes building regs and I cant see any reputable builder taking a chance on this , there would be no benefit to him.

 

[Henners]

is there something about the profile of lintels I'm missing here?
there's a lip that support bricks and a lip that supports block and channel between the two.

 

[noseall]

thats correct. the chanel will be two courses deep ( 150mm). on lintels above 2100mm wide the chanel will generaly be 3 courses deep, or 225mm.
you will need to drill through the plaster depth plus masonry in order to strike the lintel steel. usually 125mm plus.