Floor Insulation

[NCMan]

Re: Floor Insulation

I also was considering forming up, on top of the concrete hearth slab, in the shape of the oven and vent area, a pour of 4 inches of vermicrete. I think it's been done by others on here and that's where I got the idea. It looks like they used a luan plywood bendable form. I would use that or Masonite. I would probably make that pour about 4 inches bigger in area than the footprint of the WFO, to keep from losing heat to the slab, etc. I'm just weighing out my options and trying to get together a game plan. I like to get the pros and cons from you experienced builders, which I am not.

[NCMan]

Re: Floor Insulation

I did some test on this and documented the results. The test was done in ideal drying conditions. Hope this helps.

Thanks. Not sure why, but I was not able to open that file.

[david s]

Re: Floor Insulation

Yes, that's the idea. You can also use some sheet metal cut to height, it is easier to bend. Pop rivet a couple of lengths together if it's not long enough. Clamping the ends together and oiling the inside will make for easier removal.

[Greenman]

Re: Floor Insulation

I also was considering forming up, on top of the concrete hearth slab, in the shape of the oven and vent area, a pour of 4 inches of vermicrete. I think it's been done by others on here and that's where I got the idea. It looks like they used a luan plywood bendable form. I would use that or Masonite. I would probably make that pour about 4 inches bigger in area than the footprint of the WFO, to keep from losing heat to the slab, etc. I'm just weighing out my options and trying to get together a game plan. I like to get the pros and cons from you experienced builders, which I am not.

I did something similar to what you intend to do. I sized mine so that the finished dome (insulated, rendered etc) ended just over the edge of the vermicrete. That way it is sealed with no way for water to get into the vermicrete other than via the hearth.

I used very thin MDF cut into 4" strips and it bends smoothly and evenly and worked well. When I did this I poured the 4" slab and then boxed the outside up another 4" and formed the keyhole shape on top of that, poured the outside, removed the form and then poured the vermicrete. It is a good idea to have some drainage capacity in the bottom slab to allow any water that enters via the hearth a way out.

Anyway a picture is worth a thousand words. https://www.facebook.com/photo.php?f...size=960%2C720

Good luck with your build. You seem to be on the right track and there is no way you can over research or plan your build.

[GianniFocaccia]

Re: Floor Insulation

Thanks Dave,

Yes, I was happy with this session's pies, but have found that I have a lot of learning to do, with the oven as well as dough prep. I plan on sharing my (good and bad) results, but to keep things simple, I think I'll stick to posting pie pics on my OctoForno thread.

John

[david s]

Re: Floor Insulation

Thanks. Not sure why, but I was not able to open that file.

It was a zipped file and I'm on a mac. Try this one

[NCMan]

Re: Floor Insulation

It was a zipped file and I'm on a mac. Try this one

Still can't open, says it's "corrupt". Thanks, anyway. I appreciate the effort.

[NCMan]

Re: Floor Insulation

I did something similar to what you intend to do. I sized mine so that the finished dome (insulated, rendered etc) ended just over the edge of the vermicrete. That way it is sealed with no way for water to get into the vermicrete other than via the hearth.

I used very thin MDF cut into 4" strips and it bends smoothly and evenly and worked well. When I did this I poured the 4" slab and then boxed the outside up another 4" and formed the keyhole shape on top of that, poured the outside, removed the form and then poured the vermicrete. It is a good idea to have some drainage capacity in the bottom slab to allow any water that enters via the hearth a way out.

Anyway a picture is worth a thousand words. https://www.facebook.com/photo.php?f...size=960%2C720

Good luck with your build. You seem to be on the right track and there is no way you can over research or plan your build.

Steve......thanks. It may have been your pictures that I got the inspiration from. That link, for some reason, would not open, but I get the idea. Thanks again for your help.

[david s]

Re: Floor Insulation

Still can't open, says it's "corrupt". Thanks, anyway. I appreciate the effort.

OK, We'll try this way then.
Vermicrete insulating slab

The purpose of this experiment was to calculate the water loss from a vermicrete insulating slab after casting and placement.

Materials Kg Vol (L)

Vermiculite 1.82 27.00

Cement 7.25 5.40

Water 8.10 8.10

Total 17.17 21.6

For the aggregate in this mixture a 50% vermiculite 50% perlite proportion was used.
The mix is generally considered a 5:1 vermicrete and comprised of vermiculite, perlite, Portland cement, water 2.5, 2.5, 1, 1.5 by volume.
The form was filled with dry aggregate to obtain required volume, but on mixing and placing in the form, has reduced approx. 20% as some of the grains break down from abrasion during mixing and compaction on placing also reduces volume. The resulting volume reduction is an estimate based on the finished slab thickness.
Mixing was done gently by hand in a barrow.
The compacted slab was covered for one week to allow good hydration.(no additional water was added)
The weather was fine, cloudless, low humidity and the temp in the range of 12- 24 C. The slab was exposed to approx 3 hrs sun/day top surface only.
Weighing of materials was done using digital scales, but weighing of finished slab was done using bathroom spring scales as the weight was beyond my digital scales capacity.

Although the top of the slab appeared quite dry the bottom was still wet so I lifted it up, stood it on edge to assist drying after Day14


Kg
Day 7 16.0 fine
8 15.0 fine
9 14.5 fine
10 14.0 fine
11 14.0 cloudy
12 13.5 cloudy
13 13.5 cloudy
14 13.5 cloudy
21 12.0 fine
28 11.0



Conclusion
Given the ideal drying conditions, relative thinness of the slab and that it was uncovered, the experiment still demonstrates the large quantity of water present and the slow rate of removal. For a thick covered slab expect the water reduction rate to be way lower. After 3 weeks of drying more than 50% of the water had been removed by the weather from the aprox. 2” thick slab. After 4 weeks approx. 75% of the water added had been removed.

In hindsight I probably should repeat the experiment and cover it with firebrick, then compare the results. Given that the water under the floor and the base of the dome is the last to be eliminated and the resulting problems and damage it can cause, the drying of a vermicrete slab before building over it is advisable.

Sorry it's jumbled up the format a bit, but you should still be able to work it out.

[NCMan]

Re: Floor Insulation

Thanks, I appreciate that. Very informative. I've never worked w/the material before and this is all a big learning process to me. Thanks again, David.