36" Beginner WFO

[david s]

IMO stick with the tried and tested 3:!:!:! recipe. Some folk would argue that it's too rich a mix for mortar, however if the portland fails then the only active ingredient is the lime. The clay at our WFO temperature range will not be rendered permanent (sintered), so it can also be considered as a fine aggregate only, leaving the resultant ratio at 5:1.
If you alter the recipe to 6:1:1:1, then when/if the portland fails you'd be left with an 8:1 mix, too weak IMO.

Regarding sand, any fine sand will suffice.

[danjmath]

Thanks Gulf, I'll do that.
Did you use the reclaimed cuttings as thermal mass, or just in home-brew in place of fireclay?

I got a 10% box store coupon, so I am planning on ordering all the portland, lime, and possibly sand at once. Whats a rough estimate of how much I would need for 36" over(18" high)?

Also, I hear all sort of different home brew ratios.
Is the 3,1,1.,1, Sand, Fireclay, Portland, lime best, or has anyone come up with a better ratio?

Also, does the type of sand matter? Can I just go to my local quarry and load up a truck, or I am better buying the more expensive quikrete bagged sand(price may not matter to much depending on how much I need.)

*Edit-just saw quicrete playsand is on sale now as well, its a finer grained sand, would there be any problem in using that?

[Gulf]

Dan,

Sorry for the late reply. Just to add to the replys on the wood storage arch, I'm including some pics from a picasa web album of what I did. I supported a 2X8 horizontally under my arch. The top of the 2X8 was even with the top of the next to the last row of blocks. A half block was left out on each side of the form so the monolithic arch would have secure support when cured. I formed the sides with 2X material also. (I had plenty on hand.) On top of the horizontal 2X8 I placed supports to match the curve of the arch that I wanted. On top of that was 1/4" luan ply wood. Had it not been for the corbels in my build, I could have safely taken the top of the arch to bottom of the hearth slab. Since it is poured monolithic with it, there would have been plenty of support strength . I really did not do a great job of taking picks for that step But, if you zoom into the pics closely, it may be helpful. In the last pic, the black dotted lines outline the concrete blocks and show how the monolithic arch is supported . Here is the album.

I see that you are using the superdutys. Ouch! I feel your pain. I have a project going on at the moment with those bad boys. Plan for as few cuts as possible. As Russell said, only try and fit the inside of the dome for the tapers to avoid the inverted V's. If that becomes to costly in saw blades, think about reclaiming the cuttings from your wet saw. Irregardless, they will be very helpfull in filling those large outside joints without the shrinkage that is associated with the basic homebrew. Screen first through 1/4'" hardware cloth. Then through window screen. Save both steps separately. All may come in handy for grog to add thermal mass to the slim soldier course that you are planning .

[UtahBeehiver]

Dan,

You might be able to use the smaller bricks in the very upper end of the dome, say the last 2 or 3 courses where the radius is quite a bit smaller - see pic. You will have to play with the side taper to make it work. maybe alternating the taper like you will have to do for the floor. This may give you enough bricks by using both large on the lower courses and small in the very upper courses. I do not think you can do a soldier course with the bricks you have due to the taper on the bricks and the size. By cutting the large brick in half along the 9" length you will be installing 1/2 header. Nothing wrong with a soldier course, quite a few builder have been using 1/2 soldiers. Yell if you need some on site discussion,.

[danjmath]

I have a question about using a Soldier course.

I have 100 large bricks, and 100 small ones. My cooking floor is going to take ~50 of the small ones (including landing), and the rest I wanted to use mostly in the openings, as they are tapered to form arches.

According the the dome calculator, if I do the first course standard, I am going to need ~120 bricks. However, if I do a true soldier course(see attached image for what I understand a soldier course is), I will only need ~97 bricks and could do it with the brick I have.

How does it work going from a Soldier course, with a thickness of 3 inches, to a normal course that is 4.5"? Are there any large drawbacks to using a soldier course?
If so I can just but some more firebrick. It would be medium-low duty, but that shouldn't be a problem.

Thanks for all the help. I couldn't be doing any of this without all the help here.

[UtahBeehiver]

The diamond rim OD will just disappear then you will know. You can cut the 9" length bricks in half so your dimensions will be approx. 4.5 X 3 X 5.5-5.875 and the first few courses may not need any taper or bevel. Farther up the dome you will need some bevel to reduce the inverted V. Remember, shoot for tight inside joints only. You might need a little shim (since the bricks taper) get a perpendicular cut.

[danjmath]

Just got my used tile saw, and cut my first brick in half. Came with an existing blade, but I don't know how good it is. Took what felt like 5 minutes, but I do have super-duty bricks, and I was being extra cautious.

Brick seemed to cut quite slow, but the end result was super smooth.

Should I cut most of my brick in half in one go, or is there a reason to hold off and do it row per row?

Also, how do I tell when it's time to replace the saw blade. Everything I heard is you replace it when it gets hard to cut, but I have no baseline on how easy it is.

[RandyJ]

I would tend to disagree, if there were any movement in the base it could possibly damage the above slab. For example concrete poured on the exterior of buildings is not locked into the existing structure allowing it to move independently.

Most around here like to have the base all locked togather. I know that on mine I don't want anything moving on its own. I know that on large buildings things are separated but that is for expansion. You will not have enough expansion or contaction to worry about. Please make sure to lock the slab in to the base.

Randy

[RandyJ]

I also did a poored arch. I did mine as part of the support slab poor. I used 3\4" plywood front and back with 2x2" running between the plywood and 1\4" Masonite for the inside of the arch. I like the idea and personally think it is easier and stronger, so that is a win win in my book.

Randy

[UtahBeehiver]

Both Gulf and I poured monolithic arches across the oven base opening. I formed up a plywood arch made of 1/4" ply supported with 2x4 on vertical underneath. The ends of the arch form were supported by 2 X 6. I did not need a middle support although it would of been easy to slip one in. One pic shows the inside of the form and the other shows the arch form after the pour but without the 2x6 end supports.

[OT-in-TN]

Daniel, you might want to consider trimming the backer board (cutting it down a little) so that it is not completely covering up the cores of your cinderblocks. With your current design, it looks like the hearth will "float" on top of your stand and not really be locked in. Probably does not matter, but I followed the "when in doubt, build it stout" philosophy. I also had rebar in my cores that tied into the the hearth, but at minimum I'd suggest having the mechanical lock of the slab integrating into the tops of the cores.
I had a similar support along my only internal seam that I braced in the middle like you are doing, and added a few more 2-3 foot boards that I braced in the middle with an upright. I was a little nervous when I knocked out the supports, but with all the rebar I used the hearth was not going anywhere.

I would tend to disagree, if there were any movement in the base it could possibly damage the above slab. For example concrete poured on the exterior of buildings is not locked into the existing structure allowing it to move independently.

[danjmath]

After looking at some other builds I think I want to arch my Hearth Base opening.

Would it work to create an arch shape out of ply-wood for the bottom, and then have 2 other pieces of plywood front and back, then pour cement in through the openings in the cement blocks above?
If I did, how would the best way to hold up that arch shape be(just 2x4's cut to fit under)?
Would this affect the structural strength of the hearth at all(positive or negative)?
Also, if I did do that, should I pour that arch before I pour the rest of the hearth slab, or just do it all at once?

Or am I thinking about this all wrong, and there is a better way to do it anyways?
Thanks for all the advice.

[UtahBeehiver]

Daniel,

Good start, second what JR says. I used 1/2 durarock so it will hold up just add a couple 2x4s under the long spans Add some rebar in the cores, drill in, the concrete should still be fairly green and soft. Duct tape the seam of the durorock. Let concrete flow into the open cores of the wall to intergrate the durorock, hearth and drystack wall.

[JRPizza]

Daniel, you might want to consider trimming the backer board (cutting it down a little) so that it is not completely covering up the cores of your cinderblocks. With your current design, it looks like the hearth will "float" on top of your stand and not really be locked in. Probably does not matter, but I followed the "when in doubt, build it stout" philosophy. I also had rebar in my cores that tied into the the hearth, but at minimum I'd suggest having the mechanical lock of the slab integrating into the tops of the cores.
I had a similar support along my only internal seam that I braced in the middle like you are doing, and added a few more 2-3 foot boards that I braced in the middle with an upright. I was a little nervous when I knocked out the supports, but with all the rebar I used the hearth was not going anywhere.

[danjmath]

I am now getting ready to pour the structural hearth, but am a little concerned about how my backer-board is going to hold up under all that cement. I thought the backer board would be easier, because I could just leave it in. I bought 1/2" durock cement board. I am now questioning my decision, as it seems a little flimsy to hold that much weight of cement. My frame is already level with the hearth stand though.

I ran out of 2x4's, so I plan on adding at least one more support, and possibly several more. The current (horizontal in the picture) cross piece is not centered because it is under the seam between the 2 boards.
How much more support would I need to add to be safe pouring a 4" hearth on top of what I have?
Is what I am doing even going to work, or do I need to make any drastic changes?
(High quality pictures can be seen in my album).