• Post Reply Bookmark Topic Watch Topic
  • New Topic
permaculture forums growies critters building homesteading energy monies kitchen purity ungarbage community wilderness fiber arts art permaculture artisans regional education experiences global resources the cider press projects digital market permies.com private forums all forums
this forum made possible by our volunteer staff, including ...
master stewards:
  • Nicole Alderman
  • r ranson
  • Anne Miller
  • paul wheaton
stewards:
  • Joseph Lofthouse
  • Jocelyn Campbell
  • Mike Jay
garden masters:
  • Steve Thorn
  • Dave Burton
  • Joylynn Hardesty
gardeners:
  • Carla Burke
  • Pearl Sutton
  • Greg Martin

Not able to get full fire brick

 
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
I am attempting my first mass heater.  It will be on a wood floor in my home.  I see the common plan is fir two layers of full fire brick under the fire box.  I have half brick fire brick, a couple sheets of cement board, and a bunch of 2" thick pavers.  Would that work for under the half bricks to insulate the floor under the fire box?
Would get more fire brick, but $ is now a major issue and really need to get this done so we can shut off the electric heaters.
Thank you for any advice.
 
gardener
Posts: 2213
Location: latitude 47 N.W. montana zone 6A
275
cat pig rocket stoves
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Hi Thomas ;  Welcome to Permies.
Lets start with your floor.  Is it strong enough to support a rmh? We will assume that it is, or will be.
Next we need to protect the wood floor. Normal procedure is to use plain clay brick, laid flat with spacing for airflow in between. Your 2" thick pavers could work but the larger surface area would transfer more heat down into your wood. I recommend using the clay brick (home depot) and not using your pavers until the top of your mass, where they will work much better
Your concrete board goes on top of this. I recommend a double layer of 1/2" hardy board.
With only split firebrick to work with. I recommend 4" of insulated (straw) cob under the firebrick core. Hold that cob in place with a run of bricks glued (construction adhesive) around the perimeter of your cement board. If your mass is going up to a wall it should have an air gap to keep your heat indoors , not outdoors.
 
Thomas Schuessler
Posts: 6
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
As to floor strength...I will be adding 4x4 posts on footing blocks under the floor joists where the stove is to be built. (Thank you for your concern)
Will I be needing that air gap under the heated mass bench as well as the fire box? Or is the temperature enough lower there to do without? Also the back of the mass bench is against an outside wall.  I will try to get a pic of the area, and a layout drawing together asap so that my questions and answers are as clear as possible.
 
thomas rubino
gardener
Posts: 2213
Location: latitude 47 N.W. montana zone 6A
275
cat pig rocket stoves
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Better to have it all suspended. That way your gaining another warm air surface, and your floor is safe for sure.
Any outside wall should have air space or extra insulation.
 
thomas rubino
gardener
Posts: 2213
Location: latitude 47 N.W. montana zone 6A
275
cat pig rocket stoves
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Hey Thomas;   Any sawmills in your area ?  Most have a dry kiln for their lumber.  Full thickness firebricks will be in use if they do.    Simply asking (the right person) for surplus used  or new bricks might get you some bricks.  I did that and after talking to the owner about RMH's , looking at them on line...   He gave me several hundred FREE used bricks under the agreement he could come see my rmh in action!
What a deal!  There could be a similar deal waiting for you to go find... food for thought...
 
Thomas Schuessler
Posts: 6
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Long time since I originally posted here. I did end up getting a large supply of full fire brick. Finally getting started on the actual build.  I added a bunch of 4x4 post on block supports under my floor and then built a new, raised subfloor to get up to level with the rest of the house. Starting to set up my burn chamber now.
Pics of what I have so far.
20190829_151416.jpg
[Thumbnail for 20190829_151416.jpg]
Air gap
20190829_151603.jpg
[Thumbnail for 20190829_151603.jpg]
Cement board base
 
Thomas Schuessler
Posts: 6
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Laying out the burn chamber.
15671211524846727314316277804627.jpg
[Thumbnail for 15671211524846727314316277804627.jpg]
Burn chamber base
15671219260388970363969705152042.jpg
[Thumbnail for 15671219260388970363969705152042.jpg]
Burn chamber mock up with riser
 
Thomas Schuessler
Posts: 6
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Ok. Time for input from the more experienced of you.  Am I off base anywhere so far?
 
gardener
Posts: 3051
Location: Southern alps, on the French side of the french /italian border 5000ft elevation
134
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator

Thomas Schuessler wrote:Ok. Time for input from the more experienced of you.  Am I off base anywhere so far?

too much mass in the firebox and heat riser!
 
pollinator
Posts: 348
Location: Penticton, Canada
72
building woodworking rocket stoves
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Thomas,  To elaborate on what Satamax said if I may...

Look back to the first post made by Thomas Rubino "I recommend 4" of insulated (straw) cob under the firebrick core." This insulation will help stop the heat from going down towards your wooden floor. The air gap you made is great but its always good to have extra insurance. It will also help to keep more heat into the fire which is where you want it for a more clean burn. As for the rest of the stove, I see it is designed similar to the suggestions made in the builders guide. It certainly will work, but all that mass does take a fair amount of heat away from the fire especially when it is cold. Generally speaking you want as much insulation in the firebox/heat riser and mass in the heat capturing device you choose.


 
Thomas Schuessler
Posts: 6
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Ok.  Thank you! I see what you mean.  I was thinking of the fire brick as insulation, but it is more mass... Necessary mass as it is needed to withstand the direct heat of the fire, but still needing to be insulated all around for quick heatup and better draw.
It will be a few days before I can make up some straw cob, and get that layer in. Then I will mockup again and post pics before making my firebox permanent.
 
Satamax Antone
gardener
Posts: 3051
Location: Southern alps, on the French side of the french /italian border 5000ft elevation
134
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Thomas, your two layers of bricks at the bottom, could be replaced by a layer of air entrained concrete slabs, and firebrick splits atop.
 
Get me the mayor's office! I need to tell her about this tiny ad:
Heat your home with the twigs that naturally fall of the trees in your yard
http://woodheat.net
  • Post Reply Bookmark Topic Watch Topic
  • New Topic
Boost this thread!