Refractory Mortar Vs. Regular Mortar

[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.