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rafv 04-22-2008 01:02 PM

Spring has Sprung....
Just spent the past week on the coldest spring walking holiday ever. So it was great to get out in the warm spring sunshine and make a start on my oven. Well it was just going to be an oven but I am only the contractor and my 'client', The First lady of the Purse Strings, has other ideas. I have to redo the whole of the back yard. This is going to be a major job and she wants it finished by the time of our next holiday, the first week of July. Started digging up the flower beds and a Robin gave a helping hand taking away the odd grub and worm but was not interested in any heavy digging.
Now for the questions. When I got my fire bricks I also got quite a few of the softer fire bricks, 3" thick. Will these be OK to put under my hearth bricks for insulation.

dmun 04-22-2008 01:47 PM

Re: Spring has Sprung....
Insulating fire bricks are about the same in thermal value as vermiculite concrete. If you are using only them, you may want more than one layer, or lay them on edge.

gjbingham 04-22-2008 10:08 PM

Re: Spring has Sprung....
Thanks dmun. I held off on this one. I knew someone would jump in with a good answer.

Just make sure the bricks that you are planning to use as insulation are actually insulating firebricks. I have no idea how you tell the difference between the two types, but if they are not the correct type of brick, you're adding to your oven's themal mass without insulating the floor at all. Not a good idea. If you can't verify that these bricks are indeed insulating fire bricks vs. standard refractory firebricks, I wouldn't recommend using them.

Perhaps a local mason or masonry supply shop can tell you exactly what you've got.

Frances 04-23-2008 02:47 AM

Re: Spring has Sprung....
Didn't someone test this by holding a blow torch to the brick and seeing how far the heat spread?

dmun 04-23-2008 03:44 AM

Re: Spring has Sprung....
From the brick primer:


Insulating fire brick. These light-weight refractory bricks are designed to stop heat, and as such have low conduction and low heating holding capacity. They are often used to insulate industrial equipment. A typical insulating fire brick weighs about 2 lbs, compared with an 8 lb light duty fire brick.
They are very light and very soft. You can dig your fingernail into one.

rafv 04-23-2008 05:37 AM

Re: Spring has Sprung....
Thanks all,
The fire bricks I got had been used in an electric pottery kiln and the soft bricks had been used for insulation on that. I just wondered if it was a good idea to use them under the hearth rather than waste them.
It is pouring with rain today so the digging out is on hold. I was soon found some indoor jobs and I am having a quick tea break. Yes thats right, the wife has gone shopping. Better get started again before she gets back. I hope to figure out the photo thing tonight and post some pics soon. thank for now.


gjbingham 04-23-2008 08:50 AM

Re: Spring has Sprung....
I'd defer to dmun's comments. Sounds fine if they were used as insulation in their prior life.

james 04-23-2008 10:52 AM

Re: Spring has Sprung....
Insulating bricks, the light one with lots of little air holes, would make a good insulating layer under the hearth. I wouldn't go shopping for the specifically for that purpose, as there are modern insulators that are much better, but if you have them -- go for it.

For fun, take the How do They Make Insulating Firebricks quiz:


rafv 04-25-2008 03:40 PM

Re: Spring has Sprung....
3 Attachment(s)
Spring did not last very long and I spent most of the week dodging rain showers. Rain and digging out do not mix, mud up to my eyeballs (I added the eye bit just to be polite). Dispite the rain I got most of the digging done and hope to pour the concrete footings on Monday.
The pics are of an Ash tree in the garden that needed a bit of a prune, I did it a couple of weeks ago and it is now all cut, split and drying out.

rafv 04-30-2008 02:40 PM

Re: Spring has Sprung....
5 Attachment(s)
April showers have been interupting the work but tomorrow is Mayday, I just hope someone tells the weather. I could not find a photo of my stacked wood the other night so I took another one today. I did not get the footings concreted untill last thing this afternoon. On the close up photo the white bits at the edge of the trenchs are 4 1/2 inch nails put in every 4ft with a spirt level and the ends painted white. It makes getting the concrete level very easy.

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