Second attempt to build a brick oven

[cmendezg2000]

Hello to all the community, its been a couple of months that I regularly follow the forums, but this is the first time that I post.

I´m in the early stages of building a new oven for my backyard. This is my second attempt, the first one it didn't´t went so well (photo in the avatar), it was a pretty oven but was nowhere near of being functional. My first mistake was not doing proper research about the proper materials, insulation, mortars, etc. I payed a high price, I decided to destroy the oven two months ago to let the new project begin, but this time I think I did my homework, I don´t want to mess it up again, so, I would post regularly until the project is finished.

I only work in the oven during the weekends, so I will be posting updates every week until is finish. I would like to ask the community that reads this post, that if there is anything that seems out of place to help out correct the way before is too late.

Because of budget issues, I´m doing this in three stages.
1. Concrete slab, floor insulation and cooking floor.
2. Dome and entry arch.
3. Dome Insulation and finishing touches.

At the moment I finished stage 1, I´m happy at the moment with the results so far. The hardest (besides carrying all those heavy bricks) was the brick cutting part, the job was carried ok in my opinion, but I have an important question about safety, I wore a mask the whole (N95 mask), but before I go into cutting all the dome bricks, I want to ask the community about which mask are the best for this kind of job.

I leave some photos, I hope to receive some CC´s from the community.

Regards

[UtahBeehiver]

Welcome to the forum, too bad you have to rebuild your oven. A couple questions, it appears you have CaSi board under your floor fire tiles. Looks like about 60mm or about 2" this is adequate minimum amount. I do see that the floor tiles go almost to the edge of the CaSi board. This means you need to have the dome sitting on the floor tiles and not around the floor tiles. If you have the dome bricks extend down to the concrete hearth then the hearth will act as a heat sink and draw the btus away from the oven. The dome and floor need to be completely isolated by insulation from the concrete hearth. What is the purpose of the aluminum foil? A Noish 95 mask is sufficient for any work you are doing especially if you are using a wet saw to cut bricks. If you are using a dry saw, you are still protected but all the firebrick dust is going all over you work area exposing others to the silica in the brick. Keep posting and asking questions, it is easier to correct now than later.

[UtahBeehiver]

PS, it is going to be a little tough to work on the back side of the oven with the foot print going so close to the brick wall.

[cmendezg2000]

Hi Utah! thanks for your reply!

The Ceramic Fiber board is in fact 2", and yes, the dome will be sitting on top of the cooking tiles leaving and internal diameter of 105 mm. The aluminium foil I was advice to use it to stop the insulation board to absorb the water from the mortar too quickly compromising the bonding.

The concrete slab was made just in measure, on the back I have around 120 mm from the firebricks, which I was planning on using it with 2" insulation fiber blanket and 2" of insulation rendering, which leaves no space behind once finished.

Do you think that I´m lacking of insulation?

[UtahBeehiver]

You do not mortar the floor bricks/tiles or the first dome course to the floor bricks or tiles. You need to have non mortared so the dome and floor can expand and contact independently to minimize cracking. The biggest source of getting wet CaSi is from rain seeping in from the concrete hearth through the bottom of the CaSi. You are at a point where you can still drill a couple weep holes in the concrete hearth so any water can egress out. Many builders have been raising the CaSi board off the hearth by using scrap ceramic tile or thin block leaving space for water to go out the weep holes. Since you live in Monterrey I do not know what type of weather you have. maybe rain is not an issue. 2" of CaSi with 2" of insulating render (not sure what you are using) is good. 2" of CaSi board is your minimum amount but workable. Depends on the type of cooking your are going to do.

[cmendezg2000]

For the rendering, I think I will use perlite rendering (5 parts lite perlite,1 part GP cement, 1 part of lime, 1 part sand).

In Monterrey rain is not an issue, we have only a couple of months where it rains quite a bit, but the rainy season is over for this year, so, I have plenty of time for thinking about a small roof or some cover for the oven.

For the type of cooking, I like to cook about everything, from meats, veggies, breads, pasta, etc. But the main is pizza, so is intended to raise very high temperatures. I hope the insulation is enough for that, what do you think?

[UtahBeehiver]

5 to 1 for dome insulation, especially with sand in to rich and the sand reduces the insulation value (aka K value) of pcrete. You can go with a mixture of 8-10 to 1 perlite and cement then render with with a stucco coat. Attached are the K values and strengths of various rations of p/v crete. Even though rain is not a primary issue, I would still consider weep holes in the hearth and raising the CaSi off the concrete hearth. Wet CaSi board is one of the most common problems with ovens nor working well.

[cmendezg2000]

Thanks for the K values chart! nice info in there.

To drill the holes in heart, do you recommend a diameter of the holes? should I drill the holes under the insulation board also? or only on the sides? how do you raise the insulation from the concrete hearth?

[UtahBeehiver]

3/8 - 1/2" a couple places under the insulation is sufficient. As I mentioned before, some builders use ceramic tiles, others concrete pavers. I my case I used FoamGlas which is an expanded glass foam the is waterproof but is also hard to find and expensive. I would to the ceramic tile route.

[cmendezg2000]

Thank you Utah! your info is well appreciated