dmun's 36" geodesic oven part II

[Hendo]

Re: dmun's 36" geodesic oven

David,

Looking good ....

I've followed your project in detail, but may have missed something along the way. What is the purpose of the deep well under the hearth slab? Won't this make wood retrieval difficult, and/or create a potential water entry point through to your internal fireplace?

Paul.

[dmun]

Re: dmun's 36" geodesic oven part II

Hi, Paul,

That recess below the wood storage area is a sump for a sump pump. My workshop floor is built on an old garage floor slab, and is under grade. In bad rain conditions I have had need of a lower place to drain water to, and pump it out. Since I had to go three feet below grade for my footings, I figured I might as well use the space.

It will have a pressure treated floor for the bottom of the wood storage.

[dmun]

Re: dmun's 36" geodesic oven part II

Today, I'm preparing to pour the re-inforced concrete slab that supports the chimney. Since the space below will have no access, I have to use a piece of concrete board to support the slab. Since the stuff is brittle, I've stacked up some scrap insblok19 on top of my vermiculite concrete to support it in the center:



I've filled the empty space with scrap fiberglass insulation with the paper backing stripped off. Hey, why throw it out? You can see the top of the support stack sticking up in the center. Those rebar pieces in front had to be temporarily bent out of the way to get the cement board in place.



Here is the enclosure ready for the slab pour: The external brick course, that holds it, is mortared in. The cement board pieces are in place, the cross pieces of rebar are wired in place, and i've wrapped a half thickness of insulation blanket around the flue, not so much for insulation as to supply an expansion space for the hot flue.

[dmun]

Re: dmun's 36" geodesic oven part II

Today: pouring the slab. I made scrap wood plugs go go between the corbels, and started dumping concrete into the space:



Starting to smooth it out: notice the anchor bolts in the slab to secure the upper part of the tower.



No matter how stiff the concrete is when I pour it into the forms, it always seems to have too much water on it when I float it smooth. I didn't help that it was starting to rain when I was finishing the slab. I think getting mason quality finish on poured concrete is more of a skill than I am going to accquire in the course of one oven project.



After I got the slab as smooth as it was going to get, I covered it with a tarp, but that's far from watertight because a bunch of water can come off the studio roof directly onto the wet slab. It's now pouring rain, and I'm a bit worried that my portland is going to be washed out onto the lawn by morning.

[james]

Re: dmun's 36" geodesic oven part II

David,
You have done such fantastic work. Have you thought of trying to get your oven featured in a newspaper or magazine?

Of course we can't wait to see you fire it. :-) I've been working on the pizza e-book and I have pizza on the brain.
James

[dmun]

Re: dmun's 36" geodesic oven part II

If you recall, the last time we looked at the inside, it was to show the cross section of the insulation, since my oven insulation is done in two parts.



This weekend, I enclosed and insulated the oven on the inside, over the fireplace.

The first thing I did was to mortar in the smoke chamber over the rumford throat. You can see the copper pipe that acts as one of the damper bearings off to the left.



The first layer of blocks. The ones in front of the flue are cut away or thin, and are pressing against the insulation blanket, hence the bracing.



The third layer - full four inch blocks now.

[dmun]

Re: dmun's 36" geodesic oven part II

The corners were cut off by patio blocks on the diagonal, to reduce perl-crete use.



Insulating blanket was wrapped around the part of the dome still visible:



I filled the cavity with perlcrete, and mounded it up in the back to fill the arch I made when I cut through the original concrete block studio wall. I figure it can't hurt to have some extra insulation in the building, and it might help structurally if there is more settling or other motion. (Happily NJ is not an earthquake zone, of course neither was New Madrid MO)



Those two block fragments are a form for the concrete: they are standing in for the next section of flue liner.

What it looks like at the end of the day:



The top looks better than the bottom, mostly because I wasn't using random recycled concrete blocks. Still, I'm a long way from producing a finished concrete block wall. This one is going to be covered with ceramic tile or something.

[icj]

Re: dmun's 36" geodesic oven part II

Thank you for your careful and detailed photographic log of the construction of your oven and fire place. Reading through the posts and watching the development is intoxicating, like reading a book way too late into the night, but you can't quite put it down. But unlike the book there are chapters yet to be written, so may I offer my humble respect and encouragement and say I can't wait for the next post. May my own oven look half as good.

p.s. It is a pity that you have to cover up that beautiful dome with insulation, at least you can see it from the inside.

[dmun]

Re: dmun's 36" geodesic oven part II

This weeks work gets pretty perepheral to oven building, but I'm pretty much committed to documenting the process from start to finish. As you know, my oven is being built into the wall of my workshop. There is a masonry first story and a ceder and shingle finished gambrel roof second floor. This week I build a wood frame tower adjacent to my second floor.

The process starts with a sill plate. Did you know that code demands that any wood in contact with masonry be pressure treated or flashed? So, here's my 2 x 10 PT sill plate.



The slot is for clearance to combustibles. You will notice that one of my anchor bolts fell in the middle of same slot. I needed to make up that little aluminum clamp to hold down the sill plate.

Anchor bolt placement needs to be planned at carefully as anything else. More later.

The spaces between the corbels were fitted with PT nailers,



to attach pieces of crown moulding between them.



The bottom of the roof was cut away, to plan for the construction of the wall units.

[dmun]

Re: dmun's 36" geodesic oven part II

I built the wall units on the ground, with the plan to hoist them up to the second floor. Here's the front unit.



You notice that there is a careful cut on the inside of the wall to keep the wood away from the chimney by the required two inches. Notice anything? Yep, my chimney is on the other side. I had to disassemble this and put it together backwards:



Here's the outside of the left wall unit:



and the inside:



There is a clearestory window framed into the top of this side, which is on the south side of the tower, to let light into the tower all day long.

[dmun]

Re: dmun's 36" geodesic oven part II

A note on the framing: My tower is built from re-purposed timbers from someone's demolished carport, which I picked up on craigslist. Mostly what looks nasty is peeling paint. It will all be covered up. Doing my bit to keep trees standing and landfills from overfilling.

Cutting into the roof on the outside:



and the inside:



The temporary skylight:



The rafters in the middle were removed, and moved to the side to form double framing members on the sides of the opening. Here I'm lag-bolting the two rafters together:

[dmun]

Re: dmun's 36" geodesic oven part II

The big day for tower assembly arrived on Saturday. Would that I was better prepared, but life is like that. My rule-of-two on major projects is that everything takes twice as long and costs twice as much as originally anticipated.

Here's friend Chris helping with the tower assembly:



You'll notice that clever lift from the rental place. It's simplicity it's self, and it will lift a lot. Those units were hard even to stand up, let alone lift.

Everything looks better in the morning.



I was talking about careful planning on bolt placement: Here's a stud neatly pocketed to accept the nut in the wrong place:

[dmun]

Re: dmun's 36" geodesic oven part II

Here's a shot of the tower with the wall framing finished,



A little tree dappled morning sunshine never hurt anyone's looks.

Here's the sheething in progress. Sheething is not my favorite job.



Note that the sheething really adds to the stability of the structure. Even with those massive timbers, and being screwed together, the tower was pretty wobbly until the sheething went on, now it's as solid as a rock.

A photo note: If you go to the FB photoplog and you look at the images there, double clicking on them will bring up a larger version. What you see in the text are semi-thumbnails. Alternately, you can right click "open in new window" and replace "medium" with "large" in the URL, and see the full size image.

[james]

Re: dmun's 36" geodesic oven part II

As always, I can't wait to see how this comes out. Is it going to be brick? Do you have a decorative pattern?

It would be fun to see the chimney in the context of the house and the roof line. I'll bet this is going to be a great visual element for the whole house.
James

[dmun]

Re: dmun's 36" geodesic oven part II

First, to answer James' question, the top part of the tower will be covered in cedar shingles, which was a very typical construction technique at the turn of the previous century - masonry or clapboard on the first floor, and cedar shingles above. Note the flare at the bottom of the chimney, with the crown moulding below, all very much in keeping with the local construction details in the neighborhood.

Here's the tower wall sheething complete:



That little sub-roof behind an obstruction? It's called a cricket. If it's behind a chimney, as it almost always is, it's called a chimney cricket. You can file that with the useless trivia in your mind, like that the name of the cop and the taxi driver in "It's a wonderful life" are called Bert and Ernie.





The purpose of that detail is to route water and snow melt around the tower rather than into it.