Info needed please

Hi! My husband and I have decided to try to build a Rocket Mass Heater and we don't have a clue!!! We are not very good with building anything at all but our wood burning stove did not do a good job this winter and we are tired of being cold! So we want to spend this summer getting one built and ready for next winter. My husband has been watching video after video and reading anything he finds about these heaters but still we have not found the answer to the start... What do we need to put on the floor? Like under the pipes? Here's what I have going on in my house... I live in a old church that we are SLOWLY turning into our home, It is four feet off the ground the floor is a little old and weak... There is the plywood subflooring then carpet pad and carpet (which we want to tear out) I know we need to sturdy up the floor inside and out and we know what to do for that but after I get rid of the carpet and pad and there's just the plywood what type of material do I lay on top of that to be safe? I was wondering about cement board? Fire bricks? Please help.

i am new here so haven't yet built a RMH. i recommend you buy THE BOOK. inato covers everything you need to know. except the plywood floor. have a look at Mathew walkers new york restaurant build. that should give you some ideas. what is under the plywood? plywood can be quite strong but only as strong as whatever it is sitting on. there should be a load rating per sq ft for different thicknesses of ply. but not a lot of help till you know what is underneath it. HTH

The strength of the floor is not the only concern. Insulation and air space between the burn tunnel and the wood floor is required.

You can built it with legs on the bottom This will give you an air gap to help keep high heat for getting to the floor.

Thanks to everyone that has already replied to my post! These are helpful things to think about before building. We will do a lot more research and I will look into the book on it as well.

I built a small RMH(8ft by 3ft with a small bench) on a floor of pallets and 3/4in OSB plywood, standard floor structure except the sub floor is old pallets. The pallets have been reinforced and then extra post and beam support under that. But I simple put a concrete board 1/2in. on the OSB Then I put a layer of loose fill dirt around 3in. Then put the exhaust from the stove onto of that dirt and covered that. Under the Rocket part of the heater there is an extra set of paving bricks and then the fire bricks then loose fill dirt then, clay/mud. I used a 30gl drum and lots of other variations. I would build a outdoor version to make sure you have an idea of what to expect. I made several prototypes before I made one inside. Even after I built the one inside I pulled it apart and made critcal changes which made the difference between being warm and being smoked out of the small space. Hope this helps. I would aslo recommend contributing to this great site and buy any of the material which gives all the specs and really gives you the things not to do. In some ways that is the most important thing to not killing you or your family and is well worth it if you are depending on this heater to keep you warm. Remember insulation is going to be your friend. Even a giant RMH can not hold heat into a church which was meant to be in for a short period of time and not as a primary residence. With the right insulation heating becomes something that helps not wasted the energy you worked so hard to make.

We were looking into rocket stoves as well and we came across a manufactured one called the Zaug, zaugstoves.com
We wanted it to be off the ground and have the ability to cook on it, so instead of fiddling with making one we forked out and bought one. We invested in their newer model the Altaire and it performs awesome! My only issue with it was the top get too hot to cook directly on it, but that's an easy fix , just raise it.
In the near futur we will be working on creating a cooktop and ovens for it (cause the lid and outer cylinder come apart). All and all great product!