Refractory Mortar Vs. Regular Mortar Design Styles, Chimneys and Finish Discuss Refractory Mortar Vs. Regular Mortar in the Pizza Oven Design and Installation forums; I am pretty close to being finished and I ran out of refractory mortar. I only have five or so ...

[OvenBoy]

I am pretty close to being finished and I ran out of refractory mortar. I only have five or so bricks left to finish. The closest place to buy the refractory is one hour away and I really don't think I need a whole gallon to finish the job. What will happen if I use regular mortar instead of the refractory?

[dmun]

The top of the dome is a high-stress area. You need the strength of the refractory mortar there. I wouldn't use something different there, even if it was refractory, because of the expansion issues (top of the oven is the hottest part) What are you using? Maybe someone here has a little left over.

[DrakeRemoray]

I had 1 bag shipped to me, then found a local supply place (30 minutes away and only open when I am at work...). I bought a second bag from them, then had to drive up there for a third!

I ended up adding some extra mass on the outstide of the oven by coating the entire dome with the extra. I really like the results, still have a pretty rapid heat up time (about 1 hour till pizzas) and it stays hot for a full 24 hours...

Drake

[JoeT62]

Don't forget the "mix your own" option in the FB plans:

3 parts sand
1 part lime
1 part fireclay
1 part Portland cement

Except for the fireclay (which can be had by grinding down firebrick scraps) the rest of it should be able to be sourced locally. I mixed a batch of this to coat my exterior and although it was much grittier than HeatStop, it has cured up very nicely.

I will echo dmun's point about the top of the dome being the high stress area - I wouldn't use standard mortar for this if you can at all avoid it.

[BamaGirl]

I used the FB formula mortar for my dome but I used regular mortar for my tongue and chimney. Think this will be a problem later on ? How hot does the tongue get? Its about 14 inches to my opening. My oven is 37 1/2 inches in diameter with a 18 inch dome. My reveal is 11x18.

[JoeT62]

By tongue you mean vent? Or landing?

I think if it's the floor bricks it will be okay. I used the Heat Stop because I had it left over, but I had planned on standard mortar for it. If it's the vent/transition area, I might be concerned -- those gasses passing through are HOT and you actually want the heat retention to improve draw.

[BamaGirl]

My landing has fireclay and sand underneath it. I started with my vent the other day with regular mortar and then stopped. I am going to take it down and redo it with refractory mortar now before I go any further. I don't want to have problems later on. Thanks for the input.

[diy]

You can buy high quality refractory mortars from www.refractorymortars.com or www.vitcas.com
Vitcas Heatproof Mortar is ideal for setting firebricks and insulating materials, setting firebricks in room heaters, building out fireplaces and boiler areas. In fact, use Vitcas Heatproof Mortar almost anywhere you’d use ordinary mortar, but where a heat-resistant product is required.