42” Corner Build in the Shadow of Mount Nittany

[david s]

If you haven't planned it already, cast in some weep holes near the middle of the slab to save drilling them later.

[Giovanni Rossi]

Thanks David. Yes, I was all over it thanks to you and others posting reminders on the Forum!

Joined the legs from rebar in the CMU cores with more ½” rebar for the east-west runs then finished the grid with the north-south runs. Used more #6 (3/4”) rebar for added strength in the suspended section of the slab and the cantilever over the lintel.

Once I had the rebar grid worked out and secured, I could mark the position of the 1/2” PVC pipe for the 5 weep holes. I drilled through the Durock but not through the plywood in the support panel beneath. I found using zip ties to hold the tube in place against the rebar worked better than wire ties – got that idea from Joe Watson (Gulf) – I think – when he ran out of ties on a build.

Had polyester fill laying around so I stuffed some in the tubes to keep the concrete out.

[UtahBeehiver]

Bomb proof, looking great. The monolithic arch will tie in the CMUs and hearth.

[Giovanni Rossi]

Thanks for the positive comment Russell. I often show friends your copper work when talking WFOs.

Building that area of the form for the integrated arch, cantilever and angled front twisted my brain a little. I’m sorry I can’t recall who showed building a strong square frame and adding a board on the 45, but that was the ticket!

The concrete depth at the arch was going to be 14”. I wasn’t sure how much support I was going to need. I picked up a couple bottle jacks for a really good price about 30 yrs ago so I put them to use.

I couldn’t easily use braces to support the sides of the form so I used ratchet straps and added blocks in the middle to prevent bowing (again, a can’t recall where I first saw that technique on the Forum). Used another set of straps around the support legs to prevent accidentally kicking one out during the pour.

Again, many thanks to Mongo for helping me work though building the form.

[JRPizza]

That's one of the great things about this forum. Ideas get passed down from build to build till it's hard to remember who was first. Most, if not all, of my "original" ideas were copied from others

[Giovanni Rossi]

You know it JR! This forum is a well-functioning collective.

Final touches:

Ran a bead of caulk where the plywood base of the form met the CMUs. Wanted to keep the stand clean since I don’t know when / if I’ll do some sort of surface treatment.

I had some left over Hardie siding (fiber-cement composite). My daughter (architect) thought it would be an interesting detail to use that to get wood grain texture on the edge of the slab. I wasn’t quite sure how it would turn out because we would end up with the negative of the grain pattern. She also thought chamfering the top, bottom and corners of the slab would dress it up. So, I put her on the job of ripping those strips. The top chamfer would be tooled after the pour.

I was originally going to just put packing tape on the inside of the form for a release agent, but I couldn’t do that with the Hardie and get the texture. Daughter read that painting the form would facilitate release so she did that. I wasn’t convinced, especially since we didn’t have many days for the paint to cure. So, I oiled that part of the form.

Having concrete delivered for the slab-on-grade sealed the deal for me, so I ordered this batch too. Only had the family available on pour day but the wheelbarrow crew of three pushed through. This driver wasn’t as kind as the first and was unloading a little too much on each load. My wife, all 110 # of her, almost lost the balance of a load near the top of that wicked driveway. She channeled her inner Hulk and pushed though!

I wanted this batch to be firmer so I asked for a slump of 3 and it was just right. It was again 5,000 psi, but with a finer aggregate and I had them add fibers. Even though this was a thicker slab (7.5”), there was a little more waste this time (no Sonotubes to fill).

Used a bull float to level it out. Troweled it smooth after it set up a bit then worked the chamfered edge. Once the surface firmed up I added a layer of wet towels then plastic to start the wet cure.

[Giovanni Rossi]

After 7 days I pulled the 2x8 band of the form. I left the vertical supports and the jacks in place. The wood grain effect was pretty muted and there were more small voids than I would have liked. I really worked the edges with a small shovel and rod and vibrated the form with a reciprocating saw – sans blade. Maybe I should have just rented a concrete vibrator???

Some of the paint pulled from the Hardie siding and stuck to the slab. I worked that off with a wire brush. I wasn’t in any hurry to uncover the slab so I thought on things for a while.

I kept the top of the slab wet for 2 more weeks. During that time, I thoroughly scrubbed the edge of the slab with concrete cleaner to get rid of any oil or loose bits of concrete. The top and bottom chamfers were in good shape so I dressed the vertical face with a skim coat of vinyl concrete patch. I thought it came out really well. After week 3 of the wet cure I removed the support under the lintel.

Had some leftover foamboard insulation from another project so I fit some against the side of the stand. Laid some landscape fabric along the banks and filled the space between with drainage stone. Folded the fabric over the top of the stone. That brought me up to about 6 inches below the bottom of the cantilever on the back sides of the stand. Again, haven’t decided if I’m going to cover the exposed parts of the stand.

Opened the weep holes. Another pearl from Joe Watson, this time from his Simmental Farm build was to score the top of the holes to aid drainage. Used the angle grinder again…have I mentioned this is my new favorite power tool? Also, from multiple contributors...cover the bottom of the holes with screen to keep insects from nesting.

Ready for the fun? part of the project...

[UtahBeehiver]

It is all fun, just some are more fun than others. I do see a lot of ideas from various builders. Looking forward to seeing the monolithic arch.

[Sixto]

Looking good! That base is built like a WWII bunker! Fun to see how the forum inspires new builds, can't wait to see the dome progress!

Six.

[Giovanni Rossi]

Hey fellows, didn't have time to work on a post today. That big storm that ripped across the U.S. knocked out our electric service out for about 24 hrs. That was some wicked wind. I was near a tornado about 40 yrs ago and I'll never for get what the sky looked like so I always keep a look out. Didn't have any other damage but that storm certainly cut a wide path from the mid west to New England. My heart goes out to those impacted.

Yeah Russell, one of my disappointments was the arch. I really like the look of your arch and wanted to do something similar but it took me too long to figure out how to integrate and support the cantilever. I was only a day away from my concrete delivery and threw in the towel and just did the horizontal beam.

Six, had to chuckle when I read your comment. The resident architect (daughter) has been giving me the business about over engineering the base for 6 months. She just said to me yesterday when the wind was howling that if a tree comes down on the site the base will act like an anvil and the dome will be pulverized! Thanks for appreciating the references. One of my goals with this thread is to convince new builders to take the time to research the Forum before diving in.

I should have time tomorrow to get back to posting. Next up, ceramic tile.

[Giovanni Rossi]

Forgot a note in a prior post. I put the EPS board on the outside of the below grade sections of the stand because I recall reading that it may absorb some of the horizontal pressure against the stand during freeze-thaw cycles.

The next decisions were about underfloor insulation and water infiltration management.

The first thing that caught my eye was Mongo’s use of RedGard on the slab under the CaSil board. He then extended the RedGard 2” up the sides of the board and the full height and top of the board under the exterior arch. He also posted a follow-up when he lifted the floor bricks in the front to show that the RedGard held up to the temps experienced in that area.

The next was Russell’s use of a layer of Foamglas insulation under the CaSil board because Foamglas is hydrophobic. Finally, the scheme of using ceramic tiles and weep holes to channel and remove water with the understanding that it is really difficult to prevent water infiltration without using an enclosure.

So, since I’m probably going to leave the dome exposed and just use a roof structure, why not use all these techniques?

With the weep holes scored, I painted a layer of RedGard on the footprint of the insulation. Then, placed a layer of 2x2 tiles over that arranging them to keep the weep holes unobstructed. Had to buy a small amount to finish the job. My wife was glad I finally found a use for the tiles I had been saving for 35 years! Right or wrong, my thought was the RedGard would both prevent moisture from traveling up from the slab and provide a good channel with the Foamglas above and the tiles sandwiched between for water to travel to the weep holes.

[SableSprings]

Your hearth looks fabulous! It's nice to see/read that the forum's suggestions and innovations are being put to such good use by diligent builders such as yourself.

I also appreciate the effort & foresight of saving tiles for 35 years to use so productively on this project!

[Giovanni Rossi]

Thanks Mike. I know time is a precious commodity, especially for the non-retirees out there. But, this is one of those projects where good research is definitely a time (and money) saver. And most certainly, for guys like me with a limited skill set, will produce a better outcome.

Many of the aspects of this build were firsts for me. So, without the guidance and smarts found on this forum, it could have been ugly!

[UtahBeehiver]

Plus one on Mike's comments. all your research is paying off dividends. I like the addition of the grinder slots on the weep holes.

[Giovanni Rossi]

Again, I wanted the first layer of under floor insulation to be hydrophobic Foamglas. All of the oven components will sit above to isolate them from the slab to prevent water infiltration and losing heat to the slab.

This was another challenging acquisition. Foamglas was (still is?) difficult to source last year. As did a few others, I was able to find some through Distribution International. I was initially encouraged because I occasionally noticed a DI truck in my area when commuting to work in 2020. However, while there are a few distribution centers in this region, it was difficult to get a call back. And, not all stock the product.

I finally located some in western PA about 3 hrs away. They had 1 – 36 sqft package of 2-inch-thick boards. I was expecting it to cost a fortune, but it turned out to be $170 (more on that later). They also had 1” ceramic fiber blanket so I added 100 sqft to the order. The shipping cost wouldn’t be calculated until the order was confirmed. In hindsight, I should have made the trip to get it. The pandemic impact on shipping costs was impressive - $204.

I wasn’t ready to use it when it arrived. The Foamglas boards were in a 24”x24”x36” block wrapped in heavy plastic. The informational papers under the wrap were wet. I didn’t think much of it at the time as water wouldn’t impact it.

I was ready to set the Foamglas about 5 months later. My original plan was to use 2 – 2” layers. Unfortunately, when I opened the brick the boards were quite damaged. I think it’s Russell who notes how brittle Foamglas is. It’s an odd substance. It will mar at the slightest provocation but has enough compressive strength to hold the weight of the oven. I’m not sure if it was kicked around at DI considering is was the last in stock or the shipper damaged it. Once I sorted through it, I basically had enough for only one layer.

This meant that the final height of the oven floor would be 2” lower than planned.