I am currently tweaking my plans and there is an opportunity to utilise my sloped block to add an additional room under the house. The easiest and cheapest option will be by accessing it externally from the very rear of the house. My concern here is its value add as technically I am unsure what it would be classified as? Calling it a bedroom may be a stretch as you would need to go outside to access the main living and bathroom? I am Thinking man cave. The second option is changing around some of the internal layout and accessing it from inside. This is a more costly exercise but then brings the room inside where it can definitely be a bedroom/study. I have gone back to my builder for a ball park. I have a feeling the difference between the two will be about 20k. Thoughts?