I'd like to ask you for some best practice sharing, or advice .
My situation: I'm about to make new wooden floor in old house with walls made of clay and huge rocks. The walls are therefore a bit crooked/sinuous. The base of the floor is about 1,5 feet below the actual top floor level - it is approx. 1/2 ft gravel laid on earth. The room is some 16x12 feet large. I want to keep the methods as much traditional as possible (no concrete, no plastic supports, ...)
My plans: I'd like to attach steel L-profile (or wooden joist alternatively) along all walls (I want to mount it to the big rocks they should be ok to hold it) in the same level. Then I want to lay the floor joist on the L-profiles and support it in in some 3 points. On these joist I want to lay the wooden floor boards. For insulation I want to cover the gravel with foam glass up to the level of the joists. See this image: http://lowcosttraveltips.com/floor-joist-wall.PNG
- for sure it is the easiest way how to make it, but is it good idea to make it that way?
- what can I use as support "pillars"? are eg. rocks or bricks ok (I have a lot of older bricks)? or would they suck humidity and then transfer it to wood and rotten in?
- should I make any kind of hydro isolation between steel L-profiles and wooden joist and between bricks and joists?
- how many supporting pillars do I need for the joist length of 16 feet?
should I mount the floor joist to the steel L-profiles (problems with dilatation)? or can I mount it at only one side and let other side to "move"?
THank you for any help, advice and even possibly critique of my amateur ideas.