Forno Bravo Forum: The Wood-Fired Oven Community

Forno Bravo Forum: The Wood-Fired Oven Community (
-   Newbie Forum (
-   -   mortor thickness concern (

waynebergman 08-01-2007 01:37 PM

mortor thickness concern
Just read over the free manual and it is very much appreciated. Thank you Forno Bravo.
Originally I had planned to make the barrel style from Rado's site. Now thinking of the igloo. Wondering about the outer thickness out mortor gaps in this igloo design. The barrel style I was originally looking into was mentioning not to let any mortor joints get larger than 1/4" for firebricks making up the walls and ceiling, or they will crack with the high heat. The photos I have been looking at seem like there are some pretty big mortor fills, is this a concern? I realize on the iner most edges the fit will be tight and only big mortor on the outside edges but the barrel design warned against this size of moror joint anywhere on the dome.....thanks very much for helping
Wayne Bergman
Garden Bay BC Canada

dmun 08-01-2007 03:55 PM

Re: mortor thickness concern
You can cut your dome bricks to keep a less than quarter inch mortar thickness, but it's a lot of work. Most builders use plain half firebricks, and fill the outer joints with mortar. It all depends on how much you want time you want to spend at the diamond saw.

I once came up with an idea to cut every other brick to get a pretty close fit:

But I didn't actually use it.

If you look at the photogalery/dome-and-floor section of the forum you will see how other builders have dealt with the issue.

james 08-01-2007 04:56 PM

Re: mortor thickness concern
There are two different places where you can think about the width of a mortar joint. Facing into the oven itself, the joints are very thin, with the edges of the bricks just about touching (though that is more difficult as you get higher into the dome). This is that part of the oven that is exposed to the fire and the most heat. The second area is the outer edge of the brick, where the angle of the oven makes that gap larger. You can make that gap tighter by cutting an angled course of bricks in the second chain, on top of the bottom chain, to set the inward angle. Or, you can use wedges to get the right angle -- where the gap will be larger. Either way, you pack that open area between the bricks with mortar. It is in the outer reaches of the oven, where the gap does not matter.

Hope that helps.

nissanneill 08-01-2007 05:12 PM

Re: mortor thickness concern
Hi Wayne,
having just completed my Pompeii, I used the poor man's mortar, 1 portland cement 1 lime 1 fire clay and 3 brickie sand for the mortar joints rather than the latest high temperature mortar recommended. Everything is fine and no cracking. I also had the use of 14" brick saw which I used quite a lot but didn't bother with cutting all of the bricks thus reducing the mortar widths on the outside of the dome itself. I figured that the old Roman ovens are still standing after 2000 years or so and they didn't diamond saw their bricks nor did they have the technology that we enjoy today.
I agree with Dmun's idea but that will take time and money.
The choice is yours. Do you want an oven that is constructed and looks perfect (on the inside), or want an oven that cooks all of your favorite foods with a lot less fuss and cost?
You can also buy tapered bricks (at least we can here in Aus) but they will still need to be cut to form the circle of a Pompeii.
It is a lot of work to cut them accurately and time consuming. The inside will still look OK but towards the top of the dome, the gap will become wide and more obvious unless you cut every one or every second brick.


waynebergman 08-01-2007 07:10 PM

Re: mortor thickness concern
Thanks everyone...sounds like its not such a big deal. The advice from Rado's site does say even on the outside edges 1/4 inch is still too much. Maybee its the nature of that barrel design or the bricks he is using. I am still curious as why this oven would be different or maybee the advise from the barrel designers is just over kill. I will proceed with igloo as this site is suggesting. I do appretiate any further conformation to my concerns.Thanks again. Will be starting the foundation slab in a week or so.

james 08-01-2007 07:20 PM

Re: mortor thickness concern
I think you will be very happy with your choice. :-)

Do any of our recent builders have access to their dome, and can you measure how wide the various mortar joints are on the outer edge of your oven? That would be interesting to know.

Keep going Wayne.

Hendo 08-01-2007 08:29 PM

Re: mortor thickness concern

Originally Posted by waynebergman (Post 13241)
The advice from Rado's site does say even on the outside edges 1/4 inch is still too much. Maybee its the nature of that barrel design or the bricks he is using.

Or the type of refractory mortar. I'm using a premixed mortar which is designed for only 1-2mm maximum thickness. Laying the bricks is a challenge, as all contact faces must be thinly buttered with the mortar, and the brick "rubbed or tapped gently into place to produce as much brick-to-brick contact as possible."

I also purchased an alternative (dry) mortar which is OK at much greater thicknesses. I think you need to consider the specs of the refractory mortar, then work out which way you want to go regarding cutting bricks to close up the joints if necessary. But hey, plenty of members have big outer joints, their ovens are still standing and they're making great pizza!

See my post at for a couple of pics of my joints. I'm currently removing around ⅜" from the inside face of each brick, so I assume I'd end up with " gaps on the outer edge otherwise.


waynebergman 08-01-2007 10:12 PM

Re: mortor thickness concern
Thanks Hendo, your project looks nice....wayne

RTflorida 08-01-2007 10:59 PM

Re: mortor thickness concern
I kept all of my joints at 1/4" on the course to course joints. I cut all of the sides on my brick (tapered inward) and achieved a minimal mortar joint (about 1-2 mm at the most) on all side if every brick were "key" brick. I suspect the only brick movement will come the day a bulldozer terrorizes my backyard......its not moving otherwise

All times are GMT -7. The time now is 09:15 AM.

Powered by vBulletin® Copyright ©2000 - 2015, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO 3.6.0
2006/10 Forno Bravo, LLC