Tims oven - early days! Brick Oven Photos Discuss Tims oven - early days! in the Good Background Information forums; I think there may be a product you can use to harden blanket, but I am not sure, and I ...

[dmun]

I think there may be a product you can use to harden blanket, but I am not sure, and I don't know if it changes its effectiveness if you use it. If it exists.

Here's the stuff:

Refractory coating Rigidizer for Ceramic Fiber Blanket - eBay (item 140275551619 end time Oct-23-08 06:56:22 PDT)

I don't know anyone here has used it on dome insulation.

[Tim F]

Thanks for the link, I hadn't really considered the need to have such a hard surface to render over. The more I think about it, the more I think I might just use castable insulation - but I am trying to figure out the equations around heat conduction to see how much I would actually need to achieve a certain heat loss per hour (any ideas what a good target would be?)

Progress has been slow the last few days as I have been thinking about some of my design concepts. I am making an arch in the stand opening, and weighing up how I want to fit the brick around the form. I have decided that I would prefer the look if I tapered each brick so that they fit together without mortar, so I am making a jig for my saw to hold the brick at the right angle. If it turns out to be too difficult to get the cut exactly right, I will just go with the bricks un-tapered and mortared together.

I've got the supports up inside the stand, and filled the cores with rebar and concrete. I'm going to lay a piece of cement board so it just overlaps the inner edge of the stand, then pour my slab on top of that - hopefully this weekend.

[Tim F]

One more photo for tonight. I really wanted to see the arch in place so I mocked it up using some shims to hold the bricks in place.

[staestc]

Nothing better than a mock up. Looking great Tim!
Travis

[egalecki]

It looks good. I think Ken may have a chart on his thread he did with heat retention over a period of time- that may help you, if you can find it.

For me, the motto was "more is better" for insulation, so go for as much as you can fit on there!

[Dino_Pizza]

Your block stand looks great Tim. It appears you have a front opening, open all the way to the bottom of your concrete hearth base. Iv'e read about others recommending that. Is that what you are doing? Do you just lay the concrete backer-board across (& overlapping the edge of the blocks) and pour the concrete on it, with a form? or is there anything else spanning that opening. I'd like to forgo the angle iron and row of block too. I'm about ready to dig my footings and your design interest me. Good luck on it!
Dino

[Tim F]

I'm actually making a brick arch in the opening, more for decoration than anything else although it should be able to support quite a load. But if you are pouring a well reinforced slab, I can't see why you need the extra row of block across the opening. If anything, you could just sink the same bit of angle iron into your slab and get the same strength as if you had it underneath with a row of blocks on top!

I'm doing exactly as you said - laying concrete board (Hardirock) over the opening, so it just overlaps the block. The concrete board will be held up with forms inside the stand, and my plan is that the slab will tie in with the rebar that I have left poking up out of the stand as well as the rough top face of the blocks. I'll post pics as I do it!

[Tim F]

Today I made a start on actually mortaring in the arch bricks for my stand entry. Unfortunately after a few attempts I decided that cutting the bricks for the arch to the 5.5° angle required for them to fit together without mortar was beyond my brick cutting skills at this point But I think they will still look ok once the mortar is cleaned up!

I tied the verticals in my arch into the stand by drilling holes in the besser blocks and tapping nails in so that they poked out between each brick, before I added the mortar - figured it couldn't hurt.

I got the cement board and rebar delivered today, so I can set up the forms and pour my next slab as soon as the arch is finished.

[egalecki]

I actually think your arch will look better with mortar than without. I just like the way bricks and mortar look together. When you build a dome without mortar, it's not a decorative thing- it's a purely functional thing. While your arch is functional, it's also decorative.

Maybe I'm just stuck on what I've always seen, but I do also like the way dry-stack stone looks... so at least I'm not just a mortar maniac!

I don't have a header across my opening either, but it's on a corner and not as wide. Be sure to use plenty of rebar across the front of your slab- that oven's one heavy critter.

[Tim F]

Now that the mortar is in I think you are right, it looks quite nice. I've started to scrub the bricks clean with some dilute acid and they are coming up well.

I finished off the arch, yesterday. Lessons learned - it would have been a good idea to lay out my arch on the ground first, and mark off the position of where the bricks should go, so I could see if I was getting a bit off track. My biggest mistake was relying on eyeballing each brick instead of checking each one was flush with the others across the front of the arch. By the time I got to the keystone I was about 10mm out! I managed to fix it by pulling off the previous 2 bricks and mortaring them back in at a slight angle, and cutting a slight slope in the keystone brick with the angle grinder.

This morning I cut my cement board into the right lengths to cover the stand. I cut it by scoring it with a tile cutter, and then holding down a long screed (but a plank would have done it) just behind the cut, and slowly lifting the section I was cutting off the ground. I found that if I didn't do it this way, it didn't break cleanly across the score.

After that, I cut out a form to pour some concrete in the space between the side of the arch and the wall, to support the finish later on. Once this has set a bit I'll reverse the forms and fill the other side too.