I was referring more to the edges of the roof, and the colours.
The edges of the rooves in Cheydinhal are just the edges of where the tiles are, like everywhere else in Cyrodiil. The edges in Mournhold have some stone/wood/clay structure that bends up at the edges. Cheydinhal buildings are made of grey stone, white plaster, brown wood and purple tiles. Mournhold buildings are made of browny-grey stone, green tiles and a large green framy thing.
Where the hell are you getting the similarities?
I've always been under the impression that it might have been Dres architecture, as we have never, ever seen their style of construction. But we can estimate. Seeing as they live near Black Marsh, it would make sense for them to build mostly out of wood (most abundant material in the area) with heavily slanted rooftops (due to heavy rainfall).The most similar style we have seen is Indoril in Tribunal, but their roofs tend to be flat, and their buildings mostly stone.
I might have considered that, however, Cheydinhal architecture looks very similar to Chorrol architecture and shows influence from most everywhere in Cyrodiil, and looks more like a mixture of those styles. Honestly I think this is all grasping at straws a bit.