Add an upstairs floor
It will frequently happen that your ruin or barn will have a shell but no internal ‘upstairs’ - so it will need a whole new first floor adding (or replacing).
To add a new floor using exposed beams is practical and attractive, but it is quite a large job. In principle you are simply going to build the new floor with your (hopefully reclaimed) beams, and leave the beams visible rather than plasterboard the underside. If you are starting from nothing you can put plasterboard on top of the beams, so that from below you have a ‘proper’ ceiling on top of the beams. Go the whole way, and paint the plasterboard first - much quicker than painting it in situ.
Before you start you will need a structural engineer or similarly qualified prefessional to tell you what size of beams (cross-section for what length of beam) to use for your particular floor size, and the spacing between them - 60 centimetres is usual. (Read on …)