Instead of a 200mm lintel, can you not get away with using a pair of 150mm timbers bolted together..?
Also, instead of the parapet wall design, could you not have the gutter on another side of the building, or go for an internal outlet..?
Just a couple of thoughts, without seeing the plans..

If your neighbour is a pain don't bother with the parapet or the gutter- just let the water fall of the roof onto his garden / drive

Or have a flat roof with the fall to the rear- this way it will be high enough at the front

JonnyP said:

Instead of a 200mm lintel, can you not get away with using a pair of 150mm timbers bolted together..?
Also, instead of the parapet wall design, could you not have the gutter on another side of the building, or go for an internal outlet..?
Just a couple of thoughts, without seeing the plans..

Click to expand...

Hi. The garage is integrated to the house, and the new lean-to roof, which is one structure, covers the house part of the extension, and the garage. This roof is an extension of the existing roof for ease and aesthetics, so the water has no choice but to end up at the boundary.

I could of gone with a different lintel, but looking at how I am going to terminate the rafters, and the depth of the roller door, the 200mm isn't going to cause a problem.

sm0129 said:

If your neighbour is a pain don't bother with the parapet or the gutter- just let the water fall of the roof onto his garden / drive

Click to expand...

Tempted! But they have been very good this last 48hrs and we're getting on better than we ever have it seems.

sm0129 said:

Or have a flat roof with the fall to the rear- this way it will be high enough at the front

Click to expand...

As above really. Not a fan of flat roofs, and also keen to make the extension look attractive, and part of the original house.

It is all about compromises, but it looks like I can just squeeze it all in there.

I need to get hold of the supplier of the roller door and check the depth of the box on the back, though I think it was 300mm....

Cheers
Tom