Starting new 36" build

[Amac]

Re: Starting new 36" build

Hi deejayoh
Like you I have just taken the plunge and started to bulid a 36" WFO. Coincidentally I also have a similar sloped terrain, and like you I also spent the summer building a retaining wall. I decide to dispense with the wood storage. I had already started before looking in at this forum and spent the last few days admiring the various designs already completed - especially Dinos, Les and Frances in Switzerland none which I expect to emulate but I am looking forward to it. I live in Ireland and here as you may have heard we have a more than well deserved reputation for rain!. However since I had alreadt started with the Stand which is roughly 6 ft by 8 ft and right now consists of 4" rammed rubble topped by 4" in concrete. On top of that I have put a 4 1/2" slab of Vermiculite cement mix (about 5' x 5') for the undefloor insulation. My next move is to bring the concrete base surrounding the vermiculate base up to the same level and carry on from there.
I had not given any thought to the moisture absorption mentioned by SCChris. What exactly type of problems can I expect and I hope it's not too late!

Anyway I look forward to following your building as the weatger here is almost impossible right now and I expect to get little done until spring,

By the way what is really bugging me is what type of cutting tools you all used and did you rent or buy them. I really dont expect to shape the bricks for the lower layers - just cut them in halves and so on and use shims or spacers and mortar to get the dome shape.
Sorry for the rambling post!
Good Luck
Aidan

[GianniFocaccia]

Re: Starting new 36" build

DJO,
Welcome aboard. Glad to see you're already on the SketchUp plan - it will save you hours of design work. I placed my oven behind a retaining wall much like your plan, although I dug the entire oven base space out to provide for wood storage. If I can recommend one thing - it's to overinsulate I would consider going with more than just 2" of board. A number of builders have reported heat bleeding into their support slab).

Regarding effects of rain on your oven (top and bottom), consult with Keith (kebwi) who built a beautiful 36" oven in Seattle.

Congrats on taking the WFO plunge. Great-looking oven site.

John

[deejayoh]

Re: Starting new 36" build

Chris -
thanks for the input. Better safe than sorry. I think I'll dig a french drain to pull water away from the gravel under the hearth. The hearth will be above grade, so I think the main concern with water absorption is from underneath. Hopefully a french drain + waterproof barrier will do the trick.

[SCChris]

Re: Starting new 36" build

Considering that you’re in a rain heavy area, I’d spend time on how to keep things bone dry. If the foundation slab gets moist, you’re going to really fight with your oven. I’d get some method of drain so what water gets to the compressed gravel is drained off and out ASAP. Maybe create a water tight perimeter foundation wall that contains the gravel and below the gravel, install an oversized drain line. With an igloo or an oven house, you’ll need to get and keep the water away and from the portion of the slab that sits where the grass is.

This is just my opinion.

Chris

[deejayoh]

Re: Starting new 36" build

Here is a picture of the actual space. Concrete bricks are just set in there for sizing, but that is approx what the left hand side will look like. I want to have the hearth sit on top of where the grass is now.


Also - two more questions:

1) Do I need to worry about heat loss more than if the hearth was suspended? I am thinking about a 3 1/2" structural layer for the hearth, plus 2" of FB board for insulation, - but am getting a little worried about heat loss.
2) If I isolate the concrete from the soil with a plastic layer under the concrete form, do I need to worry about moisture? This is Seattle after all, but the soil seems to drain pretty well. I haven't had any standing water issues (yet...)

[deejayoh]

Hello -
After lurking here for over a year, I am finally ready to get started on the process of building my WFO. I have wanted one of these for about 10 years, so I am super excited.

My goal is to get the stand and the platform in this fall, and then begin on the construction of the dome in the spring.

My backyard is sloped, so I spent the summer installing a retaining wall and pavers to create a patio area that will be the space for the oven.

My plan is to place the bulk of the platform (~46") on top of the soil behind the retaining wall, and build a 2 foot deep stand in front of the wall to hold the rest.

This sketchup shows what I mean (although the dimensions may be a bit off).




My question is this: what do I need to do with the soil behind the wall to keep the platform stable? Is it enough to compact the soil, add 4-5 inches of compacted gravel and then pour the slab on top of that? or do I need to put in some additional support underneath to keep it from settling?

Note that this is in Seattle, so freeze/thaw is not really an issue

Thanks!

Dennis