• Post Reply Bookmark Topic Watch Topic
  • New Topic
permaculture forums growies critters building homesteading energy monies living kitchen purity ungarbage community wilderness fiber arts art permaculture artisans regional education experiences global resources the cider press projects digital market permies.com all forums
this forum made possible by our volunteer staff, including ...
master stewards:
  • Nicole Alderman
  • raven ranson
  • paul wheaton
  • Jocelyn Campbell
  • Julia Winter
stewards:
  • Burra Maluca
  • Devaka Cooray
  • Bill Erickson
garden masters:
  • Joylynn Hardesty
  • Bryant RedHawk
  • Mike Jay
gardeners:
  • Joseph Lofthouse
  • Dan Boone
  • Daron Williams

Double Skinned Bell - Do I Need An Expansion Gap Between The 2 Layers?  RSS feed

 
pollinator
Posts: 84
5
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
My latest Bell project is going to have an internal layer of clay brick/firebrick and I want to add an outside layer of slate slabs to match the existing hearth area and add additional mass to the bell.

Can I simply bond the slate to the inner brick layer with mortar or do I need to build in an expansion gap between the two layers? I noticed on the MHA site that they often use a layer of thin card between the two layers of masonry - this burns out over a period of time and leaves an air void that works as an expansion gap.

My concern is that this gap will/may? act as an insulating layer and will prevent the efficient transfer of heat from the inner brick layer of the bell to the outer slate layer.

Any thoughts or advice would be most welcome as always.
 
gardener
Posts: 2707
Location: Southern alps, on the French side of the french /italian border 5000ft high Southern alpine climate.
93
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Normally, you need an expansion gap.

We've discussed the subject with Peter, at some point. And i suggested to use wire mesh, to fill the gap, so you still have some sort of conduction, besides the usual radiation in the gap. An architect friend said, use corundum grit. But the problem there is packing, which might push the bricks, or slates during the life of the heater.
 
John Harrison
pollinator
Posts: 84
5
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Thanks for the wire mesh suggestion Satamax.
 
I am Arthur, King of the Britons. And this is a tiny ad:
Binge on 17 Seasons of Permaculture Design Monkeys!
http://permaculture-design-course.com
  • Post Reply Bookmark Topic Watch Topic
  • New Topic
Boost this thread!