Timber lintel for garden shed -acceptable?

[Lucasdemoley]

Hi,

i'm looking to install a large, 3.8m wide, triple glazed sliding door into my garden shed.

The shed is block construction with a flat roof above. The shed is about 6m long and has a central timber perlin halfway along its length supporting the rafters, and the rafters land on the wall I am proposing to install the door in.

Basically I am wondering what size timber I would need above the opening? Ive looked at the option of bolting two 2x8x4.2m treated lengths together but am not sure of the loadings. The rafters would pretty much sit on the lintel as the door is also higher than norm.

Reason for timber over steel? Cost, simple really! The door is from a building project and the frame was damaged in shipment, but it is only cosmetic, and I already have it.

Help and advise greatly appriciated.

 

[Johnmelad]

 

[Lucasdemoley]

Some pics below, not sure why they are upside down as they are on the PC the right way, weird!

You can see in the first one I have made some vertical marks on the wall to show the edge of the proposed door opening.








Help appriciated!