What size steel do i need

Ok, guys here is quite a specific question and know I maybe should get an engineer to calculate my steel, however, thought would try as there is there some great help & info available here. What we are trying to achieve is to take most of the back of the house, to extend our kitchen.
Looking from the outside we hope the steel will sit on the internal wall negating the need for a pillar so the right wall will carry straight through into the new build. The other end of the steel has approximately 600mm wall space to rest, the wall is unable to carry through. The span is approximately 4.5 meters. Approximately 3 meters of brickwork above broken up by two windows about 4m2 each. Internally the floor joists do not run into the wall so there is a bonus.
The roof is a Perlin roof with the Perlin setting back from the eves around 1.5m.
It is a 50mm cavity brickwork front and back, no blocks.
Any advice, what's more, cost-effective getting an engineer with calculations or overestimating the steel guaranteeing it will be sufficient.
Cheers, all.

 

What will be supporting the outer leaf?

Do you have some piccies?

 

Building regulations will require structural engineers calculations.
In any case there is more involved than just the load; lateral stability also needs to be considered along with existing foundations.

There are ways in which an engineer can design steels to sit on a wall at 90 without a pier....I guess you want a run of units down that wall.

 

You absolutely need a structural engineer to draw up the spec and carry out the calculations.

That way you will not have any issues with building control, your insurers or anyone else.

No alternative arguments have any validity.

 

I used an online calculator, it was cheap but my Council didn’t accept the calculations.

I ended up paying a Structural Engineer £250 to calculate 5 beams, best thing was he slightly altered the design of my loft to remove the old hips that the ‘architectural technician’ had left on the drawing.

Best money I spent on the project.

 

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