Newbie mortar question Newbie Forum Discuss Newbie mortar question in the Good Background Information forums; Hi, Does anyone know where I can find firebrick mortar in the British Columbia interior? I have found Superior 3000 ...

[skemcis]

Hi, Does anyone know where I can find firebrick mortar in the British Columbia interior? I have found Superior 3000 mortar, but it can only be used for 1/8" applications. Also have some Cercast mix, but it is pretty full of fine gravel, not something I would want to use to try and tamp into the crevices. Any help would be greatly appreciated.
I have been a background reader on this forum for a long time, and have finally gutted it up to get to the actual brick work. The hearth(s) are built on 8"*8" Spruce timbers, all sitting on 24"*24" concrete grade beams. Oven floor set in place, and awaiting the dome. Sorry no pics, spent $$ set aside for camera on brick.

[skemcis]

Ha, found one. Steel Industrial Supply in Kamloops, BC. Premix Fireclay in 25kg bags. $52.00 Cdn. Seeing as I have a 6 hr round trip to pick this up, anyone got a rough idea of how much one would use to complete a 42" high dome?

[DrakeRemoray]

For the record the HeatStop that many of us have used also says it is for thin mortar joints, but it worked fine for me.

[skemcis]

Thanks Drake. Well, I've got a 4 litre pail of it. Maybe I'll start the oven entry pillars and arch with it. Read your build blog by the way, very,very nice.
Another question, if the Pompei plans are correct, there should be no mortar showing at the inside edges of the dome. Is this doable? This is my first project with brick, and I do want to get it right.

[Neil2]

"I have found Superior 3000 mortar, but it can only be used for 1/8" applications."

This stuff works OK. For the parts that will be more than 1/8", extend the mortar mix with mortar sand mixing 1:1. The sand particles act as a "bridge" and reduce shrinkage cracks.

[skemcis]

Thanks, Neil2. Mortar sand, now does that mean I can justify using the wife's flour sieve? chuckles..... or being a little more serious, I was thinking of using window screen material in a frame, does that sound about the right size? Got lots of clean river sand here.

[Les]

Originally Posted by skemcis

Another question, if the Pompei plans are correct, there should be no mortar showing at the inside edges of the dome.

Actually, the plans have a mortar joint on the inside - it can be done without one if you spend the crazy time cutting the brick. The verdict is still out if it's the right approach because of spalling. I'll let you know in ten years

Les...

[skemcis]

Les, yeah I figured so. So here is another question. If the arc of the dome is based on the radius of the inside at floor level eg 21", a straight edge centered on the floor and reaching out to the outside of the bricks being laid, if the bricks are positioned/angled correctly the straight edge should lay flat on them, which theoretically should be true for each course. This should give me a reasonably true arc, coupled with an accurately cut keystone. Am I correct in presuming this?

[Les]

Originally Posted by skemcis

a straight edge centered on the floor and reaching out to the outside of the bricks being laid, ?

Did you mean inside? Yes, for a 42 inch dome, it's a 21 inch radius (on the inside). I cut a form that was true to ideal - you are working with brick so it will not be perfect.

Les...

[Les]

Originally Posted by skemcis

if the bricks are positioned/angled correctly the straight edge should lay flat on them, ?

I re-read your question. Do you mean if you taper every brick (inside to outside) should they lay flat? Absolutely! I advocate a dry stack - if I could do it over, I would give it a shot (but I would still be cutting brick instead of cooking).

Les...