Another question about RMH. I have a concrete slab that I will be building on for my RMH. The concrete has not been sealed. Do I need to seal the floor before I install the RMH? As a cob builder I avoid concrete because concrete wicks moisture but won’t be able to seal my floor until later this month and I would like to install the heater before it gets too cold. Thanks in advance!
Hi Diane; The important question) is the floor insulated from the ground ? Under your rmh there will be no extra moisture for the concrete to steal.
So, in answer to your question. No, the floor does not need sealing.
On to my question , is this concrete insulated ? If your answer is no ... then you will want / need 4" of insulated cob under your core and mass.The concrete will soak up your heat and transfer it directly into the ground. You can't run your stove long enough to heat the earth ....
If the answer is yes, it is insulated well... then your golden ! Build away!
Sorry, this reply is late, I've been hibernating all winter and now back at building my RMH. My foundation is 6 or 8" thick. The floor is not insulated only sealed with a sealant for concrete.
Right now the concrete slab is uneven and I plan to level it out with 2" of clay stabilized perlite that will be under the heater core. I plan to use brick around the perimeter of the bench which will be cob but unsure what to put between the slab and concrete. Someone mentioned tar paper to lay down on top of the slab and then start layering the cob for the bench. But I've also seen just broken up pieces of clay bricks (the ones with two hole in them) and I've also seen just some regular gravel as the bottom layer.
When you say insulated cob do you mean straw heavy?
The square you see--the rocket mass heater will go in there but those bricks will be laying down instead of on their side. I will level the inside with clay stabilized perlite. The L portion will be the cob bench.
Hi Diane; Welcome back! Yes, insulated cob is straw heavy. Be sure to cut your straw into 2-4" pieces. Rather than 2" I recommend 4"on the floor and you won't need any thing else.
After you have your insulated cob down . Set your pipes and carefully cover them with cob only (no straw) After that ,rock and cob in layers. The more rock the better. No air spaces.
Not all who wander are lost... J.R.R. Tolkien
We should throw him a surprise party. It will cheer him up. We can use this tiny ad: