Undercloak Installation at Gable for Small Brick and Block Lean to Extension Information, help and tips on many areas of roofing including trusses, tiling, venting, insulation etc....

[RVS6]

Hi
I am building a small lean to extension, brick/block cavity wall and concrete tiled roof. Planning to have a traditional mortar bedded verge using fibre cement undercloak. I have two queries:

1. Should the undercloak be bedded on mortar appreciating it fits under the roof batten).
2. Should the outer brickwork be set circa 10mm lower than inner blockwork height (and therefore rafter top) to allow for the mortar bedding of the undercloak? Seems to me that this would be the only way to get the required downward slope on the undercloak away from the wall face.

Any advice would be appreciated.

Thanks.