design ideas needed - wood floor

I have a wood floor, old house, with basement. Anybody able to link me an RMH design for supporting this over the wood floor? I can use jack posts, of course, but the real issue is the plate for the mass.
I actually had the thought of using ironing boards with some tubing for reinforcement directly on the floor. Stuff them with fiberglass, top them with cement board, then build from there.
Any thoughts appreciated.

Hopefully your placement will bridge multiple joists , if so 2 jacks and a beam should support the weight of the mass. As far as your wood floor, properly spaced clay brick with cement board on top will be sufficient to support the mass. This will also allow air circulation under your mass to keep the wood floor from overheating. Extra insulation under your core would be a good idea. A search of the posts here at permies or over at donkeys pro board and you should locate one about this very thing.

Kelly, you don't have an old fireplace?

Satamax Antone wrote:Kelly, you don't have an old fireplace?

No - we have a wood stove.

The most important facet of insulating the RMH from a wood floor is airflow. Lots of people have suggested or even built solid more-or-less insulating bases for this situation, but insulation, no matter how good, does not prevent heat flow, it only slows it down. Unless there is a way for the heat to escape before it reaches the wood, it will eventually build up and in extreme cases may cause the wood to char and ignite.

The spaced bricks mentioned will do the job of allowing cooling air to flow between floor and mass. Another possible method if height and weight are serious concerns would be steel studs. Lightweight C-shaped metal sections placed side by side (open sides down) can take a lot of weight while allowing cooling air complete access, at only 1 1/2" thickness versus 2 1/2" or so for bricks, and they add next to no weight beyond the actual thermal mass. The total cost would probably be similar to or less than new ordinary bricks, if you are using new materials.

Glenn Herbert wrote:Lightweight C-shaped metal sections placed side by side (open sides down) can take a lot of weight while allowing cooling air complete access, at only 1 1/2" thickness versus 2 1/2" or so for bricks, and they add next to no weight beyond the actual thermal mass.

Sounds like a good solution. Do you think cement board will definitely hold the weight with what span between the studs or bricks? Perhaps an old piece of metal roof? I suppose a small fan to blow air through the underspace would be a helpful addition, too.

The effective span of 3 1/2" means that cement board will easily work; in fact, you could probably just put cob directly on the studs, though I would use the board to help ensure that no cracks develop where the studs meet.

For the area under the combustion core, I would use a layer of insulating firebricks or perlite-clay before you start laying up the J-tube base and sides. I would tend to avoid depending on electrical aids, so there is no question of a problem if the power goes out.

Great, thanks. Next question - I'm having trouble routing the exhaust. A great solution route-wise would be to poke down into the basement, then into the chimney - which has awesome draw already. This would mean going down some 6 feet or so before going back up about 25 feet above the air intake. Will that work or create major problems.
(The mass doesn't fit by the chimney, unfortunately.)

Going 6' down before going up the chimney sounds like a real bear to get started. It might draft okay once hot, but getting there may be hard, maybe impossible without mechanical assistance. How far is the chimney from your mass location? You might need to run the flue up and over. It won't be dangerously hot, especially if you add shielding (like the next size larger duct stuffed with fiberglass surrounding the flue).