I'm planning to insulate and board out a small loft. The loft is used only for storage and is above my kitchen & bathroom. I want to fill the gap between the rafters (80mm deep) with one layer of rock wool AND then also fit loft legs, to raise the floor, and fit a further layer at right angle (170mm) to insulate above the rafters too. So, reaching the recommended 270mm of insulation. However... the gaps between the rafters are full of rubble... - brick dust, chunks of wood, plaster, old smashed up wasps nests, urgh...! None of the rubble lies above the top level of the rafters, which might be handy. Some gaps are completely full. Others are various, so an uneven surface. I'm trying to decide whether to spend a messy day or more REMOVE ALL this ****... OR taking out SOME of the rubble and rubbish to level the whole thing out out (and thus buying a 50mm deep) OR LEAVE IT and lay, as best i can, the insulation on top of it all... any thoughts anyone? thanks!