Roof truss change.

There is a prefab "low profile" truss design that adds extra height at the eves and uses a shallower pitch to give less ridge height. That does use a number of extra bracing members to achieve the stiffness. There is a picture of one here:

An extra row of block on top of the wall might be another option...

That looks very Howe-like. I now have a modified king-post/Howe design, which I have tested empirically by dangling off it. I'll see if I can post a picture somewhere.

Prefab concrete (sectional). Planning, costs are relevant.

You can post pictures on the wiki if you want... (drop me an email if you need an account created)

If you are making it higher at the eves, I doubt it matters much how you do it from a planning PoV. (and blocks are probably cheaper than timber

- although I understand the current wall thickness might be rather limited).

Not sure how, but:

The original trusses started at the top of the concrete sectional walls, and reached 2670mm at the apex. I cut and re-worked them as shown. The building would otherwise not be "permitted development" as it's only

Anyway, next hing is to finish off the trim above the concrete, fit the two pairs of doors in the front, and buy Stirling board and box profile plus odds and ends.