Building directions for portable rocket mass heater, with river rock

Hi, I want to build this in my greenhouse, and I wont be moving it, but I have a lot of river rock, so this seems a good way to me. Where do i get the directions..newbie.. thanks, lynda I am also at aquaponics in NC on facebook. I am trying to learn a lot.. thanks,

River rocks can be dangerous around fire/high heat.

Through the eons, they do absorb water (mostly through fissures). If that water is heated rapidly to high temps, the rock can explode. I would suggest 'drying' them slowly in an outdoors fire pit before trying to use them in a stove or fireplace.

alright... nice to know.. I am very green and need lots tlc.. but I will learn... cob , not being my best ability, and I am looking at the one made of the bricks at home depot or .. mastering the one made out of a water heater... just because i got river rock, dont mean i have to use them.. there is so much information,and not being a pro, it is hard to decide. I might be alone with a 12 yr old making this, so I need something easy. Is there a RMH for dummies.. city girl learning the hard way.. thank you so much, all advice needed.. my green house is 100x20 and I am in NC, so got to work it out. heat is important.. I know you guys have been at this forever, but it means a lot when you take time with the newbies.. I am training the next generation, so keep the hope flowing guys..

Well Linda.

River rocks can be used in the mass. If they crack, they won't go far being surounded by cob or mud or whatever is you infill/binder. Just make sure they're not too close to the surface of the bench. May be 4 inch or more.