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Flabuck 02-11-2010 01:59 PM

opinnions needed!
Everyone seems to have a different refractory mortar mix they like to use.The mix I use is 1 part portland,1 part fireclay,1 part lime,and 3 parts sand.I' m building an outdoor fireplace this week.What mix's do you guys prefer to use?Is my mix a good one?Thanks!

kebwi 02-11-2010 02:18 PM

Re: opinnions needed!
I used 3:2:1:1 sand fireclay portland lime. Seemed to work pretty well for me. My only mistake was that my sand isn't fine enough. It's the right material (pure white silica, beautiful white sand), but it's too big, #30. I had a hard time making a really smooth mortar for those tight gaps...although on the plus side it's probably a better aggregate for the fatter gaps than finer sand would be. I'm not sure what "better" means...more crack resistant?!

Make sure your sand is the grain size you want, something smaller than #30 if you expect 1/8th inch or smaller gaps.

nissanneill 02-11-2010 09:04 PM

Re: opinnions needed!
Hi Flabuck
I used the same as your preference and will continue to use it for future builds.
It is cheap, easy to work, doesn't have gap thickness limitations and above all, it works and works well.


kebwi 02-11-2010 09:16 PM

Re: opinnions needed!
I was only referring to the sand grain size, not the ratios...but I agree. Any variant on the homebrew is probably pretty reliable.

Flabuck 02-12-2010 06:41 AM

Re: opinnions needed!
O.k. bear with me.I,ve been a bricklayer for almost twenty years and to tell the truth I,ve never built a fireplace from scratch.I,ve built a WFO but no fireplace.So I have a couple of questions that maybe you guys could help me with.I obviously want it to radiate as much heat as possible(this is an outdoor fireplace by the way)so my question is how important are the dimensions?What I mean is how important are width,depth and height in relation to each other?And what about flue size and placement?I was just going to curve the back wall of the firebox up to meet the flue.I wasn't sure if the flue should hug the front or be placed more towards the back,or if it matters at all!I'm not able to make this thing as wide as I wanted so I wanted to make it deep.Maybe the deeper you make it the more likely most of your heat is going up the chimney.The six piece firebox kit that you can buy has nothing to it,I'ts square with a large flue centered directly above it.So I have a feeling that most of my questions don't matter but I thought I'd ask anyway cause I'm building this weekend.Thank for your help guys!

dmun 02-12-2010 07:00 AM

Re: opinnions needed!
I've built two fireplaces, and i think the best resource for this is the excellent rumford site. This plan, with a tall, angled firebox, an straight back with a curved throat, gives the best radiant heat results, as well as great draft and minimal emissions.

My oven page in my signature shows my fireplace build, including a firebrick build of the curved rumford throat.

Flabuck 02-12-2010 03:46 PM

Re: opinnions needed!
Thanks for replying Dmun.You're illustration of the curved firebrick throat is going to help alot.

Wiley 02-12-2010 10:50 PM

Re: opinnions needed!
Flabuck, Another trick to get more radiant heat out of a fireplace is to use an iron fireback. They are still available new cast and old ones can sometimes be found at second hand stores. In case you are not familiar with firebacks here's a link to a search at Amazon: fireback cast iron

Alot of the heat out of a Rumford type fireplace is thru reflection and direct from the fire. The heat from a iron fireback is almost all radiant. If the firebacks are too expensive (they certainly don't give them away) one can use a piece of heavy steel plate or recycle a bit of heavy equipment like a used track cleat off a dozer.

Hope this helps,

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