My house currently has a small kitchen with an adjacent outside toilet and then next to the toilet there is a small lean-to. I intend to extend the kitchen incorporating the toilet in the process. In addition, I would like to remove the lean-to and build a small utility room which would also be incorporated into the overall extension. As the house is semi-detatched, I want to be sympathetic to the neighbouring property and as such, I would like to preserve the pitch of the roof for the toilet and construct a new "separate" but adjoining roof for the utility room which would also be pitched but at a shallower angle. Not sure what material I would use for the roof yet (don't want felt) but would look for material suitable for the pitch that I end up with. The attached photo shows the existing tiled toilet roof and the lean-to next to it. My real question is whether the building regs require a minimum height for a utility room as whilst I would look to construct something that is higher than the lowest part of the existing lean-to, it's still not going to be particularly high.