36" in Chapin, SC

[hubert_s]

Re: 36" in Chapin, SC

Are you gauging each component? Clay and Portland shrink when they dry. What's your sand like? Sharp? Fine? Rounded?

You may be adding too much water to the mix, or it's drying too fast.

Not sure what you mean by gauging. I measure by volume and then mix with a paint mixer, slowly adding water until it has a workable consistency. I had mixed up one batch that was a bit soupy and used it in the area where the cracks are. The sand is really sharp and pretty fine. The mortar does not seem to be drying very fast at all. The left over mortar dries to a white color and even the first joints have not turned white and still look wet.

Is this going to be a problem and if so, how do I fix it?

[stonecutter]

Re: 36" in Chapin, SC

Not sure what you mean by gauging. I measure by volume and then mix with a paint mixer, slowly adding water until it has a workable consistency. I had mixed up one batch that was a bit soupy and used it in the area where the cracks are. The sand is really sharp and pretty fine. The mortar does not seem to be drying very fast at all. The left over mortar dries to a white color and even the first joints have not turned white and still look wet.

Is this going to be a problem and if so, how do I fix it?

Gauging is measuring each component to keep a consistent mix design. So, it seems that's what you are doing. Even volumetric gauging a mix will produce variance in the mix...more air here, a consolidated measure there....and effect the quality of the mortar. That said, the differences are minor, as is the impact on structural integrity of the oven itself.

Your mortar drying white tells me you are adding too much water, and possibly over mixing it. Use the paint mixer on paint....mix the mortar by hand. Also, Blending some course sand in with the fine sand will combat the shrink cracking too.

[hubert_s]

Re: 36" in Chapin, SC

Gauging is measuring each component to keep a consistent mix design. So, it seems that's what you are doing. Even volumetric gauging a mix will produce variance in the mix...more air here, a consolidated measure there....and effect the quality of the mortar. That said, the differences are minor, as is the impact on structural integrity of the oven itself.

Your mortar drying white tells me you are adding too much water, and possibly over mixing it. Use the paint mixer on paint....mix the mortar by hand. Also, Blending some course sand in with the fine sand will combat the shrink cracking too.

The mortar dries to an off white color. I use white Portland cement, so the only thing that is grey is the fireclay. Not sure if it is over mixing or the white cement.

Are you serious about mixing by hand? I honestly cannot see myself doing that. I am sore enough as it is. I'll try to be more gentle with it. I am using a low rpm drill and don't think I mix it overly long.

[stonecutter]

Re: 36" in Chapin, SC

Yeah I'm serious. C'mon, man...we're talking about a small batch of mortar for a couple courses! If you are going slow, and not mixing overly long...great

Unless I missed it, you didn't mention that you are using white Portland...so color is not an indicator..but excessive shrink cracking this early is an indicator that you have too much water in the mix and/or you need to adjust your sand.

[hubert_s]

Re: 36" in Chapin, SC

Yeah I'm serious. C'mon, man...we're talking about a small batch of mortar for a couple courses! If you are going slow, and not mixing overly long...great

Unless I missed it, you didn't mention that you are using white Portland...so color is not an indicator..but excessive shrink cracking this early is an indicator that you have too much water in the mix and/or you need to adjust your sand.

I will take a look tomorrow morning, it may only be in the area where I had the soupy mix.

[UtahBeehiver]

Re: 36" in Chapin, SC

Brick work is looking nice. I just commented on another build about making sure you have a "release" gap on you arch form. If you don't you may not get the form out without damaging your brickwork. Tip, save your form so you have a template for your oven door.

[hubert_s]

Re: 36" in Chapin, SC

Brick work is looking nice. I just commented on another build about making sure you have a "release" gap on you arch form. If you don't you may not get the form out without damaging your brickwork. Tip, save your form so you have a template for your oven door.

I planned for a 1/4 gap at the bottom, which I now realize may not be enough to get the form out. I have a computer drawing for the form, so I don't mind cutting it up when I remove it.

I did not have much time to work on the oven yesterday. The sheetrock guys wanted to hang the ceiling and I realized that there was nothing for me to fasten the enclosure walls to up top. I put in a bunch of 2x4s between the rafters.

My arch is giving me some headaches. I took a shortcut the other day and installed a brick that I knew was cut a little too short thinking it will be hidden and nobody will ever see it. Now I am looking at a 1/2" or so mortar joint. I also mocked up the arch with shims and the mortar joints get really big towards the top where the bricks angle away from each other, probably a little over 3/4". I am wondering what to do at this point. Do I cut out the brick that was cut wrong, and if so, what is the best way to remove it? Should I insert shims into the mortar joints to reduce the size? Or can I cut down the arch bricks to 3" to reduce the size of joints?

I won't be working on the oven today, so I have some time to think about it. Any ideas would be greatly appreciated.

[stonecutter]

Re: 36" in Chapin, SC

Brick work is looking nice. I just commented on another build about making sure you have a "release" gap on you arch form. If you don't you may not get the form out without damaging your brickwork. Tip, save your form so you have a template for your oven door.

What you can do is make your arch centering (form) true to size, then rip 1" off the bottom ( along the spring line) then use wedges to raise the arch to the correct height. When you complete the arch you pull the wedges and the form drops free and clear.

That's the way to do it...done on large scale vaults and bridges too.

[hubert_s]

Re: 36" in Chapin, SC

I will take a look tomorrow morning, it may only be in the area where I had the soupy mix.

I looked at the cracks again and I think I know what happened. When I put in the keystone on the third course, I must have moved the entry on the right side a little and that caused the cracks on the second course. There is one more small crack that I found on the other side. It is a vertical crack through the mortar joint between first and second course. It is aligned with gap between two bricks on the first course. The first course must have settled and caused the crack.

The mason who did all the block work and stucco on the house came by yesterday and looked at the oven. He was pretty impressed with it and did not see any problems with the mortar joints.

[UtahBeehiver]

Re: 36" in Chapin, SC

Hubert,

You can always taper your arch brick to reduce the mortar gap. Look up the "Anglizer" under General tools and they have a software program that can help you size brick taper for an arch.

General Tools and Instruments

[hubert_s]

Re: 36" in Chapin, SC

Hubert,

You can always taper your arch brick to reduce the mortar gap. Look up the "Anglizer" under General tools and they have a software program that can help you size brick taper for an arch.

General Tools and Instruments

Russel, I would love to taper the arch bricks and my first arch form had tapered bricks. When I tried to cut them on the 10" wet saw, I found it impossible to keep the brick stable enough to make the taper cut. Part of the problem is that there is a slot for 22.5 degree angle cuts in the table where the brick needs to sit. I can't make the cut on the other side because there is not enough clearance for the brick on that side.

If anybody has any suggestion how to cut the tapers I would really appreciate it. I may try to tilt the brick instead of the saw blade by cutting a 4x4 on the table saw at the correct angle.

[hubert_s]

Re: 36" in Chapin, SC

I figured out how to taper the bricks. I have to cut a 1/4" off the width and one inch off the length to avoid running into the blade guard. Still the cuts do not finish very cleanly and leave a lot of work for the angle grinder. I will try the tapered bricks.

I made a new arch form and took stonecutter's advice to leave more room to drop the form out. I figured if an inch is good, 2 1/4 inch is better and added a couple 2x4s at the bottom for stability, leaving 1/2" for the OSB floor and 1/4" for shims to level it.

I'm heading out to Chapin and hope to make some progress on the arch today.

[UtahBeehiver]

Re: 36" in Chapin, SC

Hubert,

You only need to make part of the face clean, the rest is covered by the mortar joint or your vent arch. Here is a set up I used for cutting the arch bricks and mine were 6" wide on a 10" saw, so had to cut from both ways, you can also hand feather the rough spots with your saw. Left over wedges from the dome cuts on the right side, left over straight cut in the left side to hold the brick solid while cutting.

I know you are using a better saw than to old cheapo HF so doesn't your cutting head rotate up and down to give you more height?

[stonecutter]

Re: 36" in Chapin, SC

I figured out how to taper the bricks. I have to cut a 1/4" off the width and one inch off the length to avoid running into the blade guard. Still the cuts do not finish very cleanly and leave a lot of work for the angle grinder. I will try the tapered bricks.

I made a new arch form and took stonecutter's advice to leave more room to drop the form out. I figured if an inch is good, 2 1/4 inch is better and added a couple 2x4s at the bottom for stability, leaving 1/2" for the OSB floor and 1/4" for shims to level it.

I'm heading out to Chapin and hope to make some progress on the arch today.

You should be fine, but you really don't want to prop up the centering too much. Even on my gothic vault running through my oven, I only had a drop of 3/4".

[hubert_s]

Re: 36" in Chapin, SC

I know you are using a better saw than to old cheapo HF so doesn't your cutting head rotate up and down to give you more height?

The saw head rotates up and down, but the clearance gets worse when you rotate up because the blade guard extends past the pivot point and drops when you raise the blade. I had to cut a little bit off the width and length to avoid hitting the blade guard in the rear and make the cuts in one pass. I cut all the bricks and finished them off with the angle grinder.