Hi Aggie
It’s usually suggested that it’s best not to use any preservative on hog houses. If it smells to us, it’s likely to smell much more to the hogs. I don’t know about the oils you mention. But, I have a feeling that if the hog house was wrapped in plastic sacks, it might rot more quickly and you would almost certainly get insects in between. I think the most important thing is to have a good roof, which overlaps the edges a decent amount, and perhaps raising it off the ground.
Raising the hog house of the ground a bit, is fine. Hogs are actually good climbers (probably some more than others). Although I would be worried that a seed tray is too flimsy and also doesn’t allow for much ventilation underneath. I have one wooden hog house raised off the ground on bricks (just 4 bricks at the corners). It has a brick as a step outside the door – they have no problem at all with that. Another (raised on those things you can get to raise plant tubs off the ground) has a stepping stone as a step – with a hedgehog on it, of course! but if it’s slightly higher, or you found the hogs weren’t keen you could use more steps. Offcuts of wood can also be handy for that sort of thing. i.e. making shallower steps.
My hog house with the bricks has been used for nesting, although it started life as a feed box. The hoglet made a very elaborate nest in it, coming up to hibernation time, but decided not to hibernate and used it for over day stays and naps between snacks. That’s just to illustrate the he didn’t mind the step at all, even with huge mouthfuls of vegetation to build his nest.
Good luck. Hope the hogs like the new hog house.
