Insulating Hearth Questions

[maver]

Hmmm... I don't think it will slip off. I imagine the same day pour would be more important if you used the traditional perlite as the lower layer approach. Leaving ridges should allow plenty of grip.

[james]

I think some of us suffer from the mis-guided (but well meaning) instructions in the Bread Builders book, which recommends a hearth, with the insulating layer below, hanging from a rebar grib resting on the block stand. I did it twice, and cannot recommend it - either for structural, thermal or culinary reasons.

Because the insulation layer hangs below the concrete layer, it is important in that design that the two layers be poured together to bond. In fact, I have done crazy things with nails and wire mesh to hold the two layers together. With the structural layer resting on the stand, and the insulating layer resting on the structural layer, it just doesn't matter.

As an interesting side note, I have never seen instructions for an Italian oven that recommends that you pour the same day. In fact, our producer recommends discrete insulating blocks, such as Super Isol.

Nick - you will be fine.
James

[maver]

Originally Posted by james

As an interesting side note, I have never seen instructions for an Italian oven that recommends that you pour the same day. In fact, our producer recommends discrete insulating blocks, such as Super Isol.

The Pompeii oven plans on the fornobravo website still indicate it is important to pour the same day to allow the layers to bond - maybe this can go away in the next edit

[CanuckJim]

I don't think it's important or necessary to pour both on the same day. The insulating mixture isn't all that smooth, and the slab will bond to it quite well. I used brick ties in the vermic layer to help with the bond, but mainly because I'm paranoid about such things.

Jim

[dalucca2003]

Question in regards to concrete for the hearth. I will probably pour the structural concrete part of the hearth this weekend and was planning on going to one of these rent-all places and purchasing pre-mixed concrete. Does anyone see a problem with this? I know I have seen some posts where people are recommending a fiber reinforced type of concrete. I am planning on buying the "strongest" concrete the place has to offer.

Otherwise, looking forward to this part of the construction to being completed.

[dmun]

Originally Posted by dalucca2003

Question in regards to concrete for the hearth. I will probably pour the structural concrete part of the hearth this weekend and was planning on going to one of these rent-all places and purchasing pre-mixed concrete. Does anyone see a problem with this? I know I have seen some posts where people are recommending a fiber reinforced type of concrete. I am planning on buying the "strongest" concrete the place has to offer.

I'm confused. Ready-mix concrete, around here, is delivered in huge trucks that can't go on a driveway because of weight restrictions, and have a minimum of one cubic yard for a delivery, and a maximum of 20 minutes to offload it from the truck in the street.

Do you have a place that will sell mixed concrete to go in your truck? Remember, the stuff is really heavy, and a small pickup like mine probably wouldn't do the trick.

[dalucca2003]

Originally Posted by dmun

I'm confused. Ready-mix concrete, around here, is delivered in huge trucks that can't go on a driveway because of weight restrictions, and have a minimum of one cubic yard for a delivery, and a maximum of 20 minutes to offload it from the truck in the street.

Do you have a place that will sell mixed concrete to go in your truck? Remember, the stuff is really heavy, and a small pickup like mine probably wouldn't do the trick.

There are a couple of places here locally who sell cement by the yard and provide you with the trailer to haul it. Around $80 per yard.

[DrakeRemoray]

There are also some concrete trucks that mix it as it is delivered.

These are known as "mix-on-site" trucks. They are great for smaller jobs. They may be more expensive than sack concrete for just a hearth pour, but certainly eaiser. I used this type of truck when I poured the stand (I did not use block walls for the stand). I did not use it for the the hearth pour becuase they could not mix insulating concrete. If I were using super-isol, I might have used these guys for the hearth. As it was, I was already renting a mixer for the perlcrete, and figured that I would just mix up the hearth concrete first. What a back-breaking job.

Here is a picture of the truck.

Drake

[dalucca2003]

The place I use mixes the concrete on their site, dumps it into a trailer and you haul it and unload yourself. So it sounds like it should be fine as far as structurally as I will be using the Super Isol to complete the hearth.

[DrakeRemoray]

Yes, yours sounds like a good deal. I think I paid $110 per yard + $60 delivery fee. I got 10 minutes per yard, ($1 per minute extra time) but it took longer and they did not charge me any extra.

Just for comparisons...

Drake