Bricking up an external doorway

[Djsammyc]

Hi, I'm new to this forum so please bare with me

I'm about to start converting an outhouse thats attached to the front of my house. Between the main house and outhouse is an open passage with a roof over it. Along with alot of other work, the plan is to put a door at one end and brick up the other. The building inspector wants to check it all when I'm done so I need to make sure I'm doing everything properly. I've already asked him about a foundation for under the new brickwork. He though that the foundation would carry on under the opening but after having a dig down, I've found it doesn't. He's suggested using a concrete lintel instead of digging a whole new foundation. What I need to know is

A. At what height should the lintel be put in at, ie does it need to sit on the existing foundation or can it go higher up and sit in the brickwork?

B. How do I work out what size lintel I need?

Thanks for any help in advance

 

[^woody^]

300mm below ground level

300mm wider than the opening

 

[Djsammyc]

Thanks, I should've said, I was ok with the width (150mm on either side). It was the thickness that I'm not sure of.

 

[tony1851]

If you mean the cross-sectional size, that depends on the span.
For an opening, say, 4ft wide, you'd be looking at a 140x100 p/c conc. lintel

 

[Djsammyc]

Opening is 910mm wide

 

[^woody^]

a 65mm lintel will do

 

[Djsammyc]

Thanks for your help