Modular building - scaling mesh but retaining UVs

I am creating a modular building in UE4. Most of the building has UVW mapping so that I can scale 1 meter blocks horizontally and the mapping still works (the linear bitmap UVs can be stretched in one direction - horizontally - and they will look just the same).

However, with a similar material applied to a 1 meter section of curved roof, scaling thee section will also scale the mapping which I don’t want. How do I scale the piece indicated in the graphic without scaling the bitmap?

Making modular buildings doesnt really work like that, usually separate pieces are created at the scale they will be used for and not changed (unless the scale for all axis are the same). You can mess about with world uv nodes within the material you are using to see if you can get it working.