Mention of MAPP gas is ringing a couple of alarm bells in my head.
It tends to be used where a high temperature is needed, rather than simply heat input. If the distinction between heat and temperature is not clear, it's well worth reading up on it.
"We" don't generally need higher temperatures than Propane can provide, even for forge-welding, and Propane is much cheaper than MAPP gas.
What will be the main purpose of the forge: forging, HT or a bit of both?
Do you have a particular heat source in mind? If so, do you have it already or is your choice still flexible?
What material(s) are you intending to work with initially? O1, silver steel, Old File, mystery metal?
It seems like lots of annoying questions, but the brick part of the forge is probably the least significant aspect when it comes to the difference between working well and not working at all. It would be nice to end up with something that meets your needs.
i have a knife to harden in 01 at the moment I guess I went the mapp gas route as I knew that I could get higher temps the forge would only be used for HT and not forging as such so propane is sufficient? That's good to know as you say it is much cheaper I have been watching slot of videos where people use everything from multiple propane torches to OXY acetylene and just didn't want to buy something only for it to not be sufficient for the job so as for a heat source I'm still flexible and open to suggestions