Matt's WFO Build

[mluttropp]

First of all a big thank you to James for starting this site and to everyone that has taken the time to share their build experiance with those of us that are just starting out. I am not sure I can top the documentation or the quality of build that Dinno has done but I will give it a shot.

With all the information that I have read I am getting near paralysis due to analysis and I thought it would just be best to get on with it and start to build.

My idea is to build a 42" oven with a counter top area and gas grill to the right. The idea is to end up with an outdoor kitchen.

In constructing the foundation I got a little carried away with the excavation so I have at least 8 inches of base rock compacted with a vibraplate compactor and 5 inches of concrete with wire mesh and #4 rebar around the perimeter of the slab.

The pour went well now on to the construction of the base.

[mluttropp]

Re: Matt's WFO Build

This last weekend I put together the block foundation and filled every other hole with concrete. I don't know who came up with this approach but it is fantastic for those of us with limited masonry skills.

During the layout process I found that my level slab was not so level and since I extended the base out onto the paver patio I needed to add a layer of mortar under all of the blocks in order to level everything up. Surprisingly it was not as hard a job as I thought it would be.

While I was thinking about how I was going to frame the 4 inch thick top slab it occurred to me that it would be easier if I mounted metal brackets 4 inches from the edge of the board. That way as long as the cinder blocks were level the form boards would be level. As an added bonus it made assembly of the form boards a snap. I also found that I could bend the metal bracket over the edge of the cinder block a bit and effectively lock the forms onto the cinder block base. Of course I attached all of the brackets to the boards with nice sturdy screws only to realize that this would make disassembly a nightmare. After replacing all of the screws with bolts I think I may just be ready for the slab.

I am so looking forward to being done with this part of the build so that I can actually start construction on the oven.

Ps. The two chambered storage aspect of the base was taken from Dino's build. Seemed like a great idea to me.

[Modthyrth]

Re: Matt's WFO Build

Looks like an excellent start! You'll be into the fun stuff before you know it.

If I were to build again, I'd do a two-chamber storage unit stand, too. I can hold a lot of wood in mine, but it's a real pain to crawl in there to fetch the wood from the far back wall.

[wlively]

Re: Matt's WFO Build

I can hold a lot of wood in mine, but it's a real pain to crawl in there to fetch the wood from the far back wall.

Sounds like you need to build a wood trolley to stack the wood on.



Matt

Nice looking plan. Looking forward to seeing it come to life.

[mluttropp]

Re: Matt's WFO Build

I poured the hearth slab today and it went very well. The approach of using wonderboard as part of the formwork for this slab is a simple yet very effective approach. Since I have two chambers I was able to place one sheet of wonderboard over each one with minimal cutting required. In the end all sides of the wonderboard were being supported by a couple of inches of the cinderblock. I drove a few nails through the wonderboard and into the joints in the cinderblock to keep the wonderboard from shifting around during the concrete pour. I then added a little bit of formwork in the middle of each panel of wonderboard it is clearly not strong enough to support the weight of the concrete during the pour. To test the system I stood on one leg on the wonderboard along the edge where it had the least support. Since I did not cause it to move and I weigh close to 200 lbs I figured it would be ok to pour. Fortunately I was right and all went well.

I have attached pictures of the formwork and the pour. Next step the fun stuff, laying out the insulation for the floor and starting to build an oven .

[mluttropp]

Re: Matt's WFO Build

Figuring out how to start the brickwork for the oven is turning out to be a little harder than I thought. Lots of decisions to be made and I just don?t feel like I have enough information. In looking at Dino?s work I like the idea of a tapered landing so I have decided copy his design.

Oven opening will be 20? with 22? width for the door (1? reveal) tapering out to 25? at the outer landing area.

In order to move to the next stage I realized I will need to find the answer to two rather vexing questions:

1. Should the outer course of bricks be set on insulating board or set directly on the concrete hearth slab? Dino constructed the entire oven on the insulating board material, but others have used it under the oven floor and landing only. With the latter version you end up with a brick width of material under the dome that is un-insulated. However, with the first option the dome is not ?stuck? to the concrete hearth so it may not be as structurally sound.

2. Do I need to have an expansion gap between the edge of the floor and the first ring of the dome? I have seen some use a ?? space when the floor sits inside the dome ring. However, if the dome sits on top of the floor no gap is used.

[mfiore]

Re: Matt's WFO Build

If you build the dome walls on the concrete hearth with no insulation beneath, the concrete slab becomes a heat sink. You will lose the benefit of insulation. I really think all firebrick needs to be on some sort of insulation. I built my entire dome on the insulation slab. It's heavy. Doesn't need to be mortared down. It's not going anywhere. There is even argument that the soldier course should not be mortared down to the floor, as it will allow expansion.

As for the second question, you can build either way, with the dome ontop of the firebrick hearth, or around it (still on top of insulation). If around it, I would allow a little gap for differential expansion. This gap will eventually fill up with wood ash. If the dome is on top of the floor, and you don't mortar the soldier course down, both should be allowed to expand.

[mluttropp]

Re: Matt's WFO Build

Thanks for the quick response Mike. I agree with your assesment of the heat loss I am just a little concerned that here in earthquake country one good shake and the oven may slide arround on the hearth slab.

I think I am going to build the floor inside of the dome ring just in case I need to replace floor bricks sometime in the future. How big of an expansion gap did you leave with your oven?

just finished reading the entire thread for your oven build. I am very impressed with how it has turned out. I look forward to seeing how it lookes when it is all done.

[mfiore]

Re: Matt's WFO Build

Thanks for the complements. I know nothing about earthquakes (snow blizzards are another story).

The gap was the exact width of a piece of corrugated cardboard, torn into strips. No measurements made.

[mluttropp]

Re: Matt's WFO Build

I have managed to piece together the insulating boards for the oven. I hope to play hooky from work tomorrow to buy bricks and other supplies so that I can start working on the actual oven this weekend.

I thought it might be helpful to draft up a plan for the dome. I want to be able to use a modified version of the ?indispensible tool? to help layout the dome and hold the bricks in place. This by default means that the dome needs to be a half sphere. Since my oven is a 42? oven I will end up with a 21? tall interior dimension. This is a bit different the FB plans that call for 20? but I suspect the difference will not create a problem.

I plan on cutting the soldier course with a 10.2 degree angle to allow the next row to sit flat on the soldier course. Each subsequent course will have a 6.8 degree angle between them (works out to a ?? gap between the bricks on the outside of the dome). I think this should work, but if any of you see a fatal flaw please let me know.

[Dino_Pizza]

Re: Matt's WFO Build

Hi Matt,
I was away earlier this month so I just read your posts on your base construction. It looks great. Nice job with the rebar and you'll LOVE the 2 chambers.
Your pdf section looks great to me. I think most have a half sphere and it works (proportionally) nice on a 42" oven. Your 6.8 deg cuts and 1/2" max mortar are fine IMO.
I found in my build, that I was not exacting enough on the inner edge of brick (opposite your 1/2" horizontal mortar joint on the outside) so I had a very thin to none mortar line horizontally on the inside of the dome. It's really hard to avoid. So in spite of my planning & cad drawings, my dome height crept up higher during the build so I had to make adjustments about 5-6 rows from the top to ensure the final height did not exceed 21". I think you could also watch for that and even adjust (or be forced to) sharpen your angle toward the top and shoot for 20" and you'll be close.
Do you have 10" wet saw? You should be able get enough brick dust for laying your floor after cutting the soldiers and floor. What was your plan for the high-heat mortar? Home-made or purchased? Just curious. Have fun this weekend. -Dino

[mluttropp]

Re: Matt's WFO Build

Dino,

Thanks for the reassurance on my build thus far.

My kids are already enjoying the two chambers, one for each of them to play fort in. I hope they don?t mind when I fill them chambers up with wood and other supplies .

I will definitely take your advice and plan on modifying the angles to correct for the errors that are bound to creep into the build as I move up the dome.

I managed to find a 14? wet saw on Craigslist for $125. So far all I have cut are cinderblocks for the stand build and it worked very well. The blade is a bit thicker than the HF 10? blade so I am curious how it will cut the firebricks.

I decided to go with the FB mortar as it was easier and I chickened out on the home brew stuff.

I hope to post more pictures at the end of the weekend to show my progress.

[mluttropp]

Re: Matt's WFO Build

I did not have the best start to the oven build. After I brought my pile of bricks home I decided to dry fit the oven floor just to see how it would look. At that point I noticed that the insulating boards are definitely not the same thickness nor are they all that flat. Agh.

Since I bought some fireclay and sand I decided that I should put a leveling layer under the fireboards to at least get them close the level and flat (they were 1/8" out). I used a notched trowel to spread out the clay/sand mixture and set the insulating boards. It does a nice job leveling things out. Keep in mind you will need to wet your concrete support slab before you start or the mixture will dry out nearly instantly and become unworkable. In general it is just like setting ceramic tiles.

I will try again with the floor bricks tomorrow. Hopefully I will get more done.

[Dino_Pizza]

Re: Matt's WFO Build

Sorry to hear about your tough time laying the floor Matt. But, don't worry, it'll work out.

I also bought fire clay and I ya know, I too had a harder time than I thought setting the floor. I ordered the FB boards and though they ARE 2", putting 3 together and cutting ends to fill in for a circle made for some variations. Add that to the slight variations in bricks and screeding on the the fire clay/sand mixture, tapping with a mallet & laying a level on it, it turned out to be a bit more work than I expected. If you can salvage some of the brick dust, add it to the purchased fire clay, the mix is gooeyer and sets nicer for some reason.

Also, staring at your oven floor you see edges popping up and I thought: "I'll just grind those when I'm done & it catches on the pizza peel" but you know what, it didn't matter. The only grinding and re-setting I did was on the landing area since it was noticeable. Nothing really "catches" on what I thought was uneven. Still, try and make it as flat and level as you can.

BTW: your 14" tile saw looks awesome! The FB mortar is top notch too. I went thru 4 bags and then switched to home made at the end. It's really strong. Good luck this weekend (it'll be a warm one), cheers, Dino

[Justin]

Re: Matt's WFO Build

Looking good Matt, good call purchasing the wet saw, it will make the build alot easier. Looking forward to seeing the progress