Casa100 Build - Chico CA

[Shawnr]

hillscp I probably should not be giving suggestions on this website with the experience that is here but will throw 2 cents in anyways.... I know you asked about the strapping I used on my hearth form. Looking at the form you have, I really would not trust the screws/nails at the 45 degree joints so a strap with blocking in place to ensure it is effective at those joints would be a good idea. You could scab on extra 2x4 or 6's over the 45 degree joints too. I don't know much about forming but know that a form blowing out would ruin an otherwise fun day.

Good luck!

[hillscp]

Yes, I'll put two pieces of scrap 1/2" hardie backer under each cross member. That should put it a little under the middle

[UtahBeehiver]

Are you going to raise the rebar off the duracrete floor?

[hillscp]

Getting a little done each day. It finally started raining in Nor Cal (which is good). Got some snow at Lake Tahoe and on the coast range. Winter is coming!. We'll be skiing in no time I'll be looking for a dry weekend to get the hearth poured.

[hillscp]

All I have time for today. Headed to San Francisco to watch the Giants Dodgers playoff game. Go Giants!

[hillscp]

Thanks Shawnr - Not building the house yet just thinking ahead. Good idea with the straps. I think I'll try that!. Great idea putting the mixer up on blocks!

[Shawnr]

As to the screws question, I backed up the screws with a couple of ratchet strips. The blocking mid way also helped keep the sides from bowing. Seemed to work ok for me but I am one of the least experienced ones here. Thought the photo might help you though. See post #13

A friend lent me a mixer but I would have gotten one, but I am lazy. And I think the mixer does a better job. My hearth was like 57" x 63" ish and I used 19 bags. I have seen videos of guys doing much larger jobs by hand but wow, lots of work. I think not having to mix allows more time to work with the concrete in the form.

Everything I have read about the hearth on here just mentions the rebar in the configuration you mention. Not sure why the mesh is skipped but I would guess that with that close a matrix of rebar, the mesh is redundant. In the base, the rebar is only laid around the edges so the mesh helps in the middle.

Re the taping of the seam, I did the support slightly different, a plywood bottom that was removed. I put a 2x6 under the seam to support its length, and I taped it.

I am starting my steel stud frame soon too and have not done much with them either. I consulted a carpenter friend and he gave me a few pointers and ideas.

I am confused...you are building the house before the oven?

[hillscp]

I am getting close to pouring the hearth. After that I have a lot of design decisions to make. I'm pretty sold on building a "house" out of metal studs and hardi backer covered in stucco and tile trim.

First things first though; the hearth. I'm using the instructions that came with the kit for reference. They are somewhat ambiguous and downright contradictory in some cases .

Here is my plan for the Hearth construction

• Build a support structure inside the block base using 2x4's. Start by creating a support around the inside edge then suspend horizontal members from the edge support. Leave the vertical supports a little short and shim them underneath so they can be adjusted and removed easily.
  • Question - How far apart should the horizontal cross members be? The widest span is 47" so I'm thinking one horizontal member should do? That leaves ~24" between horizontal support members. I have a recurring nightmare about the whole thing falling down.
• Lay 1/2" hardi backer on the support frame and across the top of the block
  • Question - I have worked with hardi backer before laying tile. Is there any reason to tape the seam in the middle?
• Build a form around the perimeter with 2x6 lumber and 2x4 vertical supports. The concrete should be 3.5" plus .5 inches of hardi backer making a 4" thick hearth.
  • Question - How should the form members be fastened at the corners? Just screws through the lumber and into the end grain? I have a fear of it coming apart. Screwing into end grain scares me.
  • Question - can I be successful mixing 18 60lb sacks of concrete in a wheelbarrow with a hoe or should I rent a mixer? Reasoning is that I'm not sure how fast I need to be getting all the concrete in the form
  • Question - How far apart should the rebar be. Instructions say 1/2" rebar 12" on center. Should I add mesh?

Thanks in advance. the next thing will be framing the house with metal studs. I've never worked with them before.

[Gulf]

For future builders following: My advice is to not use a release agent of any kind for a surface that will be tiled. The rough surface is what you want anyway.

[david s]

Yes, scrub it with detergent, let it dry, paint on an acrylic tile sealer, then tile, using a quality outdoor tile adhesive.

[hillscp]

PAM is spray on cooking oil. I did use it sparingly. Almost pure canola oil. Maybe I'll scrub it with detergent, I want to tile it.

[david s]

I’m not sure what you used as a release agent, I use mineral oil/kerosene 50/50, but it can interfere with the bonding of any subsequent coating applied over the casting if you don’t scrub it off. That’s part of the reason I dilute the oil and apply it sparingly.

[hillscp]

I pulled off the front of the form. Looks really good (to me)! Little steps and victories. Just in case you were wondering - PAM works great as a release. I'll leave the inside of the form up until later this evening. I'm going to have to cut out the center members so I can pull the sides away (the screws face the concrete)

[hillscp]

I tied the rebar to the block and poured the lintel today. I'll remove the form tomorrow after work. 24hrs should be enough? I put 4 pieces of rebar in the top. Went pretty smoothly.. My daughter helped.

The only thing of note was that the epoxy I bought to anchor the rebar was a disaster. It cured way too fast and clogged up the applicator. I ended up throwing it away and getting some portland based anchoring cement. Much cheaper and far easier to work with.

[david s]

As the inventor of this little innovation, that I’ve been using for 13 years, I should be speaking with some authority, but I’m really not sure. I use a single hole, around 12mm (1/2”) in diam, cast into the precast supporting slab for our product. It works pretty much like the little hole in a saucepan lid, both reducing steam pressure as well as providing a path for water drainage either liquid or vapour. In this regard the larger the number of holes the better I should think. I often remind myself of a new electric kiln that I fired empty (according to manufacturers instructions) up to device temperature. At around 400C (750F) around 100 ml of water began dripping out from one front bottom corner. The water in the refractory, being driven out hitting the cooler metal outer casing, condensing and running down the sides to exit via gravity at the front corner. I was surprised that this occurred at such a high temperature. This also led me to design a venting system to allow steam pressure relief and a pathway for water vapour between the inner and outer domes to the atmosphere.
regarding the mesh over the holes I prefer to place it on the inner or upper side of the slab, but this is only possible if it’s glued on before the floor insulation is laid over it.