Installing a fixed window in a cavity wall

I work as a handyman, but most of my work is joinery, kitchens etc. Have been asked by customer to put a small window in cavity wall, he says keep it long & narrow and it wont need a lintel! I'm a bit sceptical. I've put internal lintels in before for doorways, but dont know if what he says is true ( about one & a half to two bricks wide). Its location is upstairs, only a couple of courses down from the ceiling (though he would be happy enough if it was higher).
Any advice would be much appreciated, particularly any theoretical maximum width that would be safe without a lintel
Bob

Even to fit this one window if you are not fensa registered it would need you to submit a building notice for building regs. and most authorities would expect to see some support above an opening even a small one .

and even if you are fensa registered and fit a lintel this is structual work so would still need a building notice.


Its ok customer saying fit it this way it will be fine . Mark my words first sign of a problem and customer that very nice man who said " oh it will be ok do it this way " suddenly turns into a different person and your the rogue trader that every one talks about. when he has trading standards etc on your back.

Frankly you would be a fool to carry out this work even with the customers request not to use a lintel

Your duty as a professional would be to carry out your work properly, safely and to any relevant standards.

If you did not install a lintel then you would be responsible for any subsequent problems and no disclaimer or waiver from the customer would remove that responsibility - and your PL insurance may be invalid too.

Thanks guys, point(s) taken.
Bob