Mortar Joints

[Ken524]

Re: Mortar Joints

That keystone has a familiar shape to it

[K79]

Re: Mortar Joints

Ok guys.... So if I could achieve a 3/8" mortar joint between all my bricks that would be ideal correct???

[Tscarborough]

Re: Mortar Joints

Unlike normal brick and mortar, the normal joint for firebrick and refractory cement is 1/8-1/4", so that would be ideal, although not practical for an oven. Just keep them as small as possible on the interior face and don't worry about the outer joint (stuff it full of mortar).

[K79]

Re: Mortar Joints

Unlike normal brick and mortar, the normal joint for firebrick and refractory cement is 1/8-1/4", so that would be ideal, although not practical for an oven. Just keep them as small as possible on the interior face and don't worry about the outer joint (stuff it full of mortar).

I'm speaking out of ignorance here, but why can't 1/4" be achieved or practical?

[Tscarborough]

Re: Mortar Joints

Because you are building a spherical object out of cubic units.

[K79]

Re: Mortar Joints

So here is a drawing of what I was planning on doing. Please let me know if this is even possible, with a really good blade and a wet saw. Also please keep in mind that my mind works like an engineer and the saying goes "looks good on paper but what about in the field". So I drew up my oven on AutoCAD. I have all of my angles and plan on plotting out everything to scale for my layout. Now for cutting the brick: I chose for this example my 9th and 10th ring because the angles are exaggerated the most. The bricks that are drawn on the computer are flat and need to be elevated at the rear to create the dome. So if I take a stencil of my flat 9th layer brick and overlay it with my stencil for my 10th layer brick I'll know how much needs to be shaved off and at what angle for my next (10th) ring. The blue shaded area would represent the cut. This way I could achieve a 3/8" mortar joint all around. Assuming laying brick is like drawing it on a computer haha

[K79]

Re: Mortar Joints

That keystone has a familiar shape to it

I've watched your video so many times.... is there any other way to do it

[Tscarborough]

Re: Mortar Joints

You could build the oven with no mortar, technically, but practically, the simple answer is: Keep the joints as small as possible on the face and don't worry about them on the back side.

Mortar is not used to hold brick together, it is there to hold them apart, i.e. fill in the gaps of imperfect units and allow a manufacturing tolerance to be established. This is why good firebrick are dry pressed, not wire cut; the designed tolerance for fireplaces and other refractory structures is a joint of 1/8". For normal brick the design tolerance usually requires a 3/8" joint, reflecting the manufacturing capability of fired brick.


Why not make all brick by dry press? Cost and texture considerations.

[K79]

Re: Mortar Joints

You could build the oven with no mortar, technically, but practically, the simple answer is: Keep the joints as small as possible on the face and don't worry about them on the back side.

Mortar is not used to hold brick together, it is there to hold them apart, i.e. fill in the gaps of imperfect units and allow a manufacturing tolerance to be established. This is why good firebrick are dry pressed, not wire cut; the designed tolerance for fireplaces and other refractory structures is a joint of 1/8". For normal brick the design tolerance usually requires a 3/8" joint, reflecting the manufacturing capability of fired brick.


Why not make all brick by dry press? Cost and texture considerations.

should I be looking for dry pressed and not wire cut?? What did you use?

[Tscarborough]

Re: Mortar Joints

Almost all firebrick are dry pressed, wire cut are easy to tell, they LOOK like they were cut, dry press are slick on all sides.

[deejayoh]

Re: Mortar Joints

K79 -

Have you downloaded my dome calculator spreadsheet? It will do all the math for you on the angles for every course. Lets you adjust the mortar joints however you like. Probably helpful if you haven't. It's linked in my sig below

And for cutting bricks, I'd advise looking at Hendo's twist and tilt thread. You use a jig to cut the bricks, not a template.

I think you are maybe reinventing some stuff that folks have figured out already

[K79]

Re: Mortar Joints

Very handy I?ll be looking this over. My method from my drawings should allow me to cut out to scale a stencil for the brick. The brick for each ring should all be the same dimensions with the exception for around the vent (same dimensions only some custom cuts into them).

[deejayoh]

Re: Mortar Joints

The issue I see with a stencil is that the top of the brick is smaller than the bottom - so it is hard to get the angle right for the brick as you cut it.

That's why the jigs are so great. You set up the jig for each course, and then you can run all the bricks you need (except the last, as you will find...) for that course at once.

[K79]

Re: Mortar Joints

The issue I see with a stencil is that the top of the brick is smaller than the bottom - so it is hard to get the angle right for the brick as you cut it.

That's why the jigs are so great. You set up the jig for each course, and then you can run all the bricks you need (except the last, as you will find...) for that course at once.

Can you explain the jig setup to me?

[ATK406]

Re: Mortar Joints

Take a look at the thread "Tapering with a 10" saw" under Tool, Tips and Techniques. It should be pretty self explanatory.