Old Bricklayer New Challenge

[Hans O. Lowe]

Hello all, I'm Bob from Iowa. Out of high school I entered the family trade as a Bricklayer (after a short stint as a tender). Although I've been out of the trade for over a decade, I think I can still do the work. I've had interest for years in pizza and wood fired ovens and have decided to finally take the plunge and start the process of learning the best practices in oven building. I look forward to the challenge and I'm excited to be on the forum.

[UtahBeehiver]

Hey Bob,

Welcome, since you have mason skill, you are ahead of the curve on building an oven. Most of us were have or had nominal brick laying skills. That said, we survived and made WFOs. To give you a design and basic concept of WFOs, download the cheap/free eplans from the FornoBravo retail store site. This is a great baseline for designing a WFO, a little dated but concepts are solid. Also go to the Newbie Section and under a sticky call Treasure Archives you will see several of the more documented builds that also include improvements on the eplans.

[Hans O. Lowe]

Thank you for the welcome. I'll go download the plans now. I have kind of a basic idea of the concept after studying some of the Italian builders' pictures. (on pizzamaking.com) Someone in that thread commented that this forum had vastly improved on their antiquated practices (paraphrasing) so I came here to do some learning. I haven't had much experience with perlite, and the only vermiculite I ever used was as a dry-fill insulation in CMU cores.

[UtahBeehiver]

Perlite and vermiculite/portland mix can be used a budget insulation on these ovens but the new high tech insulations are really more effective but do cost more. Looks at the Treasure Archives to get some ideas.

[david s]

The extra cost of commercially available insulation materials needs to be weighed against the labour of making and applying the vermicrete or perlcrete as well as the time and effort of eliminating their water content.

[Hans O. Lowe]

"as well as the time and effort of eliminating their water content"

By this, do you mean, an extended curing time?

[UtahBeehiver]

I'll try and answer for David. P or Vcrete has a lot of water in the mix and has to be removed either by extended drying by natural or heat from the ovens. Using P or V crete is used for floor insulation is particularly difficult to remove if one start the brick floor before the mixture is completely dry. Wet insulation is one of the major factors for poor oven performance, this include CaSi board (for floor) and ceramic blanket (for dome) . It typically takes twice as much p or cvrete thickness to equal CaSi or ceramic blanket thickness. So in a nut shell, if your insulation is or get wet it will take longer to cure the oven. Attached is a pic showing p/vcrete ratios and insulation values.

[david s]

Here is an experiment on drying a vermicrete slab that explains the free water content and its removal that you should find interesting.
Vermicrete insulating slab PDF copy.pdf

[Hans O. Lowe]

UtahBeehiver, thank you for that table and the information about the insulation taking in water. I guess I never thought about vermiculite and perlite taking on water.

[Hans O. Lowe]

David s, I appreciate that pdf of the drying test. I did indeed find it interesting. I'm going to print that out and make a binder of notes.

Looks like bricklayer does not equal oven-builder!

[david s]

UtahBeehiver, thank you for that table and the information about the insulation taking in water. I guess I never thought about vermiculite and perlite taking on water.

The table also shows the relationship between density, strength and insulating value. You can make it stronger, but that reduces insulating capacity. Conversely you can make it more insulating, but that reduces strength.
Builders have found that because the underfloor insulation needs to support significant weight a 5:1 mix is required, but for insulation over the dome, where strength is not a factor, just enough cement to bind the grains together and to make application, particularly on a vertical surface, a 10:1 mix woks ok. Some builders have gone as lean as 13:1, but I find 10:1 as lean as is comfortable for me to handle.

[MarkJerling]

Hello all, I'm Bob from Iowa. Out of high school I entered the family trade as a Bricklayer (after a short stint as a tender). Although I've been out of the trade for over a decade, I think I can still do the work. I've had interest for years in pizza and wood fired ovens and have decided to finally take the plunge and start the process of learning the best practices in oven building. I look forward to the challenge and I'm excited to be on the forum.

Welcome from New Zealand!
You'll find lots of helpful members so shout out if you have any questions.
Kind regards,
Mark

[Hans O. Lowe]

Thanks, Mark! I have found this to be a very welcoming forum. I have spent some of my spare time reading and printing off some stuff. Russell and David have been great about pointing to resources, which leads to a rabbit hole for me!

I sure enjoy the research and learning. It's getting late in the year to build an oven outside for me unless I build a mobile oven in my shop this winter. I guess I won't rule that out!

[Hans O. Lowe]

The table also shows the relationship between density, strength and insulating value. You can make it stronger, but that reduces insulating capacity. Conversely you can make it more insulating, but that reduces strength.
Builders have found that because the underfloor insulation needs to support significant weight a 5:1 mix is required, but for insulation over the dome, where strength is not a factor, just enough cement to bind the grains together and to make application, particularly on a vertical surface, a 10:1 mix woks ok. Some builders have gone as lean as 13:1, but I find 10:1 as lean as is comfortable for me to handle.

Great information, thank you. I was initially planning to do the entire base in insulating concrete. After the information you have given me, I might do a structural base and an insulated pad under the dome only.

[UtahBeehiver]

Structural base and insulating pad is the most common approach. I don't think a p/vcrete structural base is sufficient for strength and have the needed insulation properties at the same time.