Castable - How thin can you go?

[mikku]

Re: Castable - How thin can you go?

Its funny stuff this sand, last week it was an insulator now its thermal mass.

Now what? Tag team wrestling? You and Laurentius?
But--I don't have a partner!
Go ahead! Show me what you got! I'm a big boy!

[david s]

Re: Castable - How thin can you go?

Its funny stuff this sand, last week it was an insulator now its thermal mass.

It's both actually. It will take ages for the heat to penetrate it but because of its mass it will hold heat too. If you want it as a thermal mass you need to fill in all the spaces between the sand grains with cement and lime, then it works as a good conductor.

[david s]

Re: Castable - How thin can you go?

Great looking build! Simple and functional! You even figured out a way to put it on and take it off a vehicle for transportation!
Next question--can you go thinner?
If you were going to do "this style again" what would you change?

I went as thin as I dared and it works pretty well.
The next one I make, I won't use the Hebel as a supporting slab. It does not seem to be strong enough. Although it has 5mm steel bars cast into the panels, they have cracked, either from the heat or the weight bouncing on them. It's been over corrugated roads and speed bumps. I will replace it with concrete next time, although it is 3 x heavier.

[david s]

Re: Castable - How thin can you go?

Hello Tcarborough,
Those were some of my thoughts in post #4.
The order is different, I mentioned loose fill because I wanted to leave the option of adding additional thermal mass for the non-pizza enthusiasts!

Thought the loose fill would allow for the dome to move completely independant of the hard coat/perclcrete. Your design would use both the hard coat and insulation as support for the dome. The only nagging question--is there enough mass then with 1"?

I don't think loose fill, or blanket are suitable for this application. Vermicrete provides a much better structural support. You don't want the inner dome rattling around inside unsupported.

PS I think you should concentrate on finishing your current build and learn from that before designing a new one. Wait until you have finished and start using your oven to see how it goes. By the way I didn't say anything before but I think you are going to find your entry is way too long to be able to work comfortably and efficiently. See how it goes.

[mikku]

Re: Castable - How thin can you go?

That is the case here in Oz too. If you build a "brick veneer" house, it is a wood frame house lined on the inside with gyprock (plasterboard) and a single skin of brick on the outside. The roof trusses are supported by the timber wall frames, the outer single thickness brick skin (the veneer) is not considered a load bearing element. It is not even considered stable enough to stand up by itself, it must be tied back to the timber frame. (I agree with this by the way, I've seen a few single skin walls fall over.)
It usually ends up with an argument. The carpenter puts up the stud frame walls, the brickie lays the bricks alongside the stud frame, with the galvanised ties laid in the mortar. The sparky runs the wires, the plumber runs the pipes, then the gyprocker, (sheet rock installer to the US cousins) comes in and says "Mate, no one has nailed the brick ties to the studs. You sure you want me to nail up this gyprock?".
At that point the brickies say, "not our problem mate, we lay bricks", the chippy says "not mine, my job's finished when the frame is up", the gyprocker says "F-off, I don't do that shite, I'm a gyprocker and plasterer".
(This is the same guy who is too lazy to cut the penetrations with a hole saw, he belts holes for the power points and water taps in the gyprock with a hammer. The front of the sheet looks alright, the back looks like he shot it with a 12 guage. She'll be right, mate, the flusher will fix that.)
Then if you are like my mate, the homeowner does it himself, if he catches it in time, and the tradies spend their lives wondering why homeowners, who just spent their life savings on a new home, hate them.

Got no problem with brickties, but the USA brickies nail them to the studs as they go up, other end gets mudded into brick holes. Good brick masons stateside also have a membrane at the bottom that channels water that might penetrate into the in-between cavity--also weep holes.

When I mentioned- no fire rating... Some areas where we build are designated as fire zones. There the walls must be made up things that will add up to a certain level of protection. If you add a brick veneer to any part of the house, it is graded as "zero"- meaning that it does not add to any fire resistance of the structure. So you have to put something--Brown sheetrock, siding with a rating etc...anything that is on the list!

I don't think you have to put 9mm rebar into the brick build as you go vertically do you? Here you do! Maybe they are added in 2' sections as you go--but you have to weisel the brick over the rebar to get it into a bed of mud! Those are some stupid rules!

If some of the mates acted the way you say--I would send them packing very quickly.. I realize how difficult it is to get a loan, and pay it off-- done it a couple of times..

USA builds are the same, except when the inner structure is masonry as well and then the inner masonry (instead of the framing) becomes the support, exterior always is veneer only.

Good to see some things in common between hemispheres!

[mikku]

Re: Castable - How thin can you go?

I went as thin as I dared and it works pretty well.
The next one I make, I won't use the Hebel as a supporting slab. It does not seem to be strong enough. Although it has 5mm steel bars cast into the panels, they have cracked, either from the heat or the weight bouncing on them. It's been over corrugated roads and speed bumps. I will replace it with concrete next time, although it is 3 x heavier.

So your Hebel must be what we call "Power Board", if that is true--it comes in modular sizes about 2 feet tall--in lengths you order based on manpower? Cuts with the same saw shown--my build cutting oya stone!

Still needs painting & joint caulking?

There might be some alternative lightweight aggregates that might work on a base for a homebrew base casting.

[david s]

Re: Castable - How thin can you go?

So your Hebel must be what we call "Power Board", if that is true--it comes in modular sizes about 2 feet tall--in lengths you order based on manpower? Cuts with the same saw shown--my build cutting oya stone!

Still needs painting & joint caulking?

There might be some alternative lightweight aggregates that might work on a base for a homebrew base casting.

Yes i think that's the stuff. Here it is a CSR product called Hebel and they call it "Power Panel" . Mine came in 75 x 600 mm and I cut the lengths I needed.
Alternative lightweight aggregate, use perlite or vermiculite. I sometimes use 50/50 or 60/40 perliight and 7mm blue metal aggregate if I want a lighter weight concrete. But remember, if you lighten the concrete by using a lighter aggregate you also weaken it by approx the same amount.

[mikku]

Re: Castable - How thin can you go?

It's both actually. It will take ages for the heat to penetrate it but because of its mass it will hold heat too. If you want it as a thermal mass you need to fill in all the spaces between the sand grains with cement and lime, then it works as a good conductor.

Some designs for infloor radiant heating (elevated areas) have PEX tubing run beneath framed floor, other have tubing above the floor with stripping to create a cavity, some use nothing in the cavity, some recommend concrete in the cavity, others say to use sand.

My home has stripping over the regular subfloor (1 1/2") height, spaced at 455mm (Japan module for 2x4 framing) in the cavity between the stripping are my heating tubes (1/2" PEX) and the rest is filled with a very low cement content sand mixture. Just enough for the stuff to retain its shape. Above that is oak strip flooring. This creates a very even heated floor surface. I am sure that sand would do the same--drawback, when using a vacuum cleaner--winter months when the flooring dries and small cracks appear; possible for dust to be drawn from below.

Sand as an insulator--lots of applications, earth berm structures, even that Walsh oven earlier described... "if only inner brick, sand, outer brick" what is the sand called? both an insulator and a thermal mass. I think when determining the characteristics you have to identify the materials being compared. Then each can be labeled in relation to the other.. if that makes sense?

Must be difficult living in a world with no colors or shades of gray!

[mikku]

Re: Castable - How thin can you go?

I don't think loose fill, or blanket are suitable for this application. Vermicrete provides a much better structural support. You don't want the inner dome rattling around inside unsupported.

PS I think you should concentrate on finishing your current build and learn from that before designing a new one. Wait until you have finished and start using your oven to see how it goes. By the way I didn't say anything before but I think you are going to find your entry is way too long to be able to work comfortably and efficiently. See how it goes.

Thanks for the heads up.
The dome was cast as well as the entry way before I checked into this forum.
I guess time will tell.. My earliest posts asked the exact thing you are pointing out now. I hope that it will draw properly.. On a future casting, I might be able to reduce the distance by 5 maybe 6 inches. All early work was done entirely on the fly.. Only time I referenced anywhere was determining the oven opening size---any oven shown on net ...never any concern about width---when looking at different models of ovens.. a standard began to appear on their dimensions-oven height vs door height. I ended up fine--same goes for stack size... It is all a learning curve.

This current exercise is called "multi-tasking", like walking and chewing gum at the same time. Keeps my mind off pretty ladies!

As far as the last line goes--"if you only drive "Chevies, you don't know the pleasures of driving a "Lexus? or Benz or Rolls"

Thanks!

[mikku]

Re: Castable - How thin can you go?

Yes i think that's the stuff. Here it is a CSR product called Hebel and they call it "Power Panel" . Mine came in 75 x 600 mm and I cut the lengths I needed.
Alternative lightweight aggregate, use perlite or vermiculite. I sometimes use 50/50 or 60/40 perliight and 7mm blue metal aggregate if I want a lighter weight concrete. But remember, if you lighten the concrete by using a lighter aggregate you also weaken it by approx the same amount.

A friend of mine has a precast business. Some of his products are underpin pieces used to stabilize ground. The product is called "KOMA", don't know if they are on internet. He sells both regular concrete precast "koma" in 300mm diameter, the larger 500 or 600mm diameter he offers in a light weight version. He must maintain a certain standard of strength for both--but I do not know his alternative aggregate. I did see it delivered in mesh "1 ton" bags, similar to the way he receives some of his cements--other in trucks?

These Koma are used instead of piling where soil beneath a proposed structure is not adequate to carry the load. Also under large parking areas instead of huge volumes of infill. He has scientific data showing how it supports structures in areas with high water table--subject to liquifaction under earthquake conditions--performs very well and very cost effective.

Amazing--another similarity different hemispheres

[mikku]

Re: Castable - How thin can you go?

Over here I think bricks would have quite a good fire rating.

Rebar would be an earthquake thing. In my lifetime of 52 years, I can only remember one earthquake in Oz that actually damaged houses.

I guess I wasn't clear enough - my mate was the homeowner.
The "tradesmen" were locals he knew socially though.
It was a while ago and I learned a lot from his experience - it's all about knowing what questions to ask. Just ask your plasterboard installer how he's going to cut the holes and he realises you won't settle for bashing a hole with a hammer.
When you ask your brickie or chippy for a quote, ensure you are clear who's doing what.
They tell me that, these days the average Aussie house is bigger than the average American house. Who'd a thunk it?

That is exactly my point--some stupid rules that do not recognize that "yaki mono", things produced by the firing of clay at high temperatures --have a fire rating. Brown sheetrock, paper each side with a modified gypsum has but not brick! CRAZY.

Hardest thing to face is a friend "the homeowner" on the street and to explain someone elses poor work on his house.. The same amount of material can build a truely good house that will last a very long time ---as a crappy one.. The difference is the attitude of the people putting it together!

I don't know house sizes in USA anymore, average sizes vary here by location--all depends on the price of the land. Some places in Tokyo land sells for hundreds of thousands of dollars per m2. Usually it is sold in units of 3.31m2 called a "tsubo". Normal nationwide is $2000 to $5000 per "tsubo". Tough to swallow those prices and still put a house on the land! My house total space is only 1500 sf.

My view of a house is this: build it the size you can afford and feel comfortable in..nothing more or less, and you will be fine!