My partner and I are young and have been living for a few months in a small brick house of 84 square meters (3 rooms and a kitchen). We have no children and no plans in the near future. But of course, it's something we both want! That's why we've talked about possibly expanding when children become relevant. Or moving, as my partner suggests. However, I am very happy with both the house and the location. By summer, we will probably change the roof. My father then suggested that we build upward since we're already "on the way," while my partner's dad said NEVER, it's more expensive. What's actually cheaper? Building up or out? We had (read I) planned for a 38-degree non-elevated roof that should provide about 40-50 square meters extra, and we were thinking of approximately the same size if we built out. We were planning to hire for most of the work because we're unskilled, and our parents simply have very little time. It's a bit difficult because our parents have completely different views about building up or out, and we listen and believe our own fathers, so we almost end up arguing..!
I would be very grateful for advice and help!
I would be very grateful for advice and help!
if you're going to change the roof anyway, it would reasonably be cheapest to build upwards, as you would avoid the cost for a slab and the like.
keep in mind that a stairwell also takes up some sqm...
keep in mind that a stairwell also takes up some sqm...
Get in touch with some construction companies and ask for a quote 
That way you'll have actual figures to work with.
Operating costs are a bit lower by building upwards as well, since you can make better use of the heat.
That way you'll have actual figures to work with.
Operating costs are a bit lower by building upwards as well, since you can make better use of the heat.
Also check how it's going with building permits in either direction. You might not be allowed to build sideways/upwards. In that case, it resolves itself.
Also consider the layout, do you want to avoid running up and down stairs for the rest of your life? How will the rooms be placed? Etc. etc.
Otherwise, I agree with mats_o.
Also consider the layout, do you want to avoid running up and down stairs for the rest of your life? How will the rooms be placed? Etc. etc.
Otherwise, I agree with mats_o.
Think twice about that 38-degree roof pitch. It steals a lot of space compared to a mansard roof and is not that much cheaper. For example, look here to see how much difference there is between the roof types: http://www.minhembio.com/speedomac/45353/