Particle boards and parquet don't exactly sound like a playhouse, but we all have different levels of ambition 
If you have a draining layer of macadam underneath and it's airy enough, it shouldn't be necessary.
But in a traditional beam layer, you have a subfloor of oil-hardened board.
If you have a draining layer of macadam underneath and it's airy enough, it shouldn't be necessary.
But in a traditional beam layer, you have a subfloor of oil-hardened board.
Built a playhouse in 2010 on lecablock, just one block per beam so completely ventilated underneath, didn't even remove the grass, kit from Beijers with untreated tongue and groove of weak caliber as the floor, placed a plastic mat as a floor inside on top of the tongue and groove, was quite worried the first 2 years, it deteriorated significantly according to me but probably didn't really, I was just being a perfectionist. Then it was played in for maybe 10 years, had another child a few years later. Now it has been a pot storage for 5 years and I don't care at all about its condition, but it seems to be exactly the same as 10 years ago, fresh but not newly built.