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mluttropp 07-06-2009 09:42 PM

Matt's WFO Build
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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 07-06-2009 10:00 PM

Re: Matt's WFO Build
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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:mad:. 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 07-06-2009 10:45 PM

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 07-07-2009 11:02 AM

Re: Matt's WFO Build

Originally Posted by Modthyrth (Post 59205)
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. :)


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

mluttropp 07-11-2009 01:09 PM

Re: Matt's WFO Build
3 Attachment(s)
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 07-12-2009 09:43 AM

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 ¼” space when the floor sits inside the dome ring. However, if the dome sits on top of the floor no gap is used.

mfiore 07-12-2009 10:38 AM

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 07-12-2009 11:43 AM

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 07-12-2009 12:06 PM

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 07-23-2009 10:15 PM

Re: Matt's WFO Build
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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 ½” 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.

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