WE have purpose built our goathouse after not really finding anything that was suitable. OUrs is concrete slab, then wooden. It is fairly high (2m one end and 2.4 on the higher side), with LOADS of ventilation (louvre principle) above headheight, and measures 3m x 7.20m. Size was dependent on not having to cut too much timber, but it has four pens of 5ft x 8ft and a large central (milking) area. Double doors to make sure we could get deadstock/wheelbarrows out easily, all wood is screwed and can easily be removed/repaired. Doors have outer wooden doors and mesh on the inside, so can leave open all day for fresh air and light, if weather means that goats are in during the day. Also have double glazed (!) windows (from the skip of the local glazing company just down the road), with the inside protected by mesh.
We had snow inside last winter, came in through the ventilation, but my goats were fine (no rugs) on their deep bedding.
Water and electricity also there. (as goats insist on Radio 2 during the day!)
Can't post any pics, as working from laptop and pics are on PC....
Anke