Heat a garage? Mortar mix recipe? Building plans?

1) could I heat a garage with this and would I build indoors or out side?
2 ) formula for mortar mix, and are there detailed plans available?

http://batchrocket.eu/en/applications#threebarrel

http://donkey32.proboards.com/thread/1817/starting-build-220mm-rocket-double

Hi Bob; welcome to permies!  Yes you can heat your garage with a RHM . Recommended to build a core & riser  outdoors to get the hang of it but then you would build your RMH  in place. The builders guide by Ernie & Erica Wisner readily available on amazon will have all the tech info your wanting.  Two different burner styles , the original J tube design or the newer batch box version. Both are outstanding.  J tubes are quick and relatively easy to build  , batch boxes are much more technical to build but burn slightly longer and hotter than a J tube. There is currently a batch box core built with ceramic fiber board and stainless steel that is available on Ebay , produced by a permies member. As your first rmh I recommend a J tube ... you can always upgrade to a batch box later.