Simple Loft Conversion - Method to remove tie without walls splaying.

[GeoPar]

I'm assuming this will have a simple answer but I just want to get an engineers advise. I will consult a local S.E when it comes to building regs but just looking for some preliminary advise / ideas before submitting the planning application.

I'm working on a loft conversion however head height is extremely tight (1935mm). I have attached a section that I have sketched the structure over the top of. The steel (binder?) beams - positioned below the studs - I have allowed to be whatever size they need as these wont effect the head height. I have sized the joists at 195mm (ideally I was hoping to reduce this to 150mm). I am conscious that I am removing the existing joists (to lower the ceiling) and a tie (as can be seen in the attached photo). I'm assuming this will cause the walls to splay outwards. I therefore assume I need to introduce some sort of beam running from eaves to eaves to prevent the walls from doing so but I'm worried this will effect head height. I know in older houses they used to use the metal bar anchor plates - Would this be a solution?

Section Sketch:

http://files.engineering.com/getfil...1-c55a-4e8c-a450-219dd5dc5abe&file=sketch.pdf

Plan Sketch:

http://files.engineering.com/getfil...8251-4fc3-a627-e6b12793eec8&file=sketch_1.pdf

Image One:

http://files.engineering.com/getfil...0554-4aee-9df7-3cd36101805d&file=IMG_2472.JPG

Image Two (showing tie to be removed):

http://files.engineering.com/getfil...90b4-45ed-a6f7-e2b75b97520a&file=IMG_2474.JPG

 

[Teguci]

I'd look at designing a lateral beam along the top of both walls to collect the outward thrust from the rafters and transfer it to new ties at both end walls.

 

[msquared48]

This lateral beam could also be the ceiling diahragms to each side of the new opening with whatever shear walls below it are3 needed for stability.

Mike McCann, PE, SE (WA)