28" Oven in Seattle

[JRPizza]

I got my fireclay at Mutual Materials - they have a store in South Seattle. Got my bricks from them too.

[UtahBeehiver]

You need to go to a masonary/brick supplier for brickie clay. HC Muddox is a brand available in the US and inexpensive.

[david s]

You can search also for Bricklayers Clay. If that draws a blank try Ball Clay from pottery or ceramics suppliers. Some folk have just used fine sand as a leveller. I think the clay/ sand mix produces less movement under the bricks because the clay, being finer , fills the spaces between the grains of sand.

[JBA]

On the topic of fire clay - does it go by any other name? I am unable to find any at the big box stores (Lowe's and Home Depot) in Seattle. Worst case, I might have to settle for refractory mortar mix which is more expensive.

When setting the floor of the oven on top of the CalSil insulation board the Forno Bravo guide suggests using a mix of sand and fire clay under the floor bricks. Is there any other combination of materials that would work in the absence of fire clay?

[JBA]

More progress on the oven from the past two weekends.

Stand is complete and the mold for the hearth has been completed. Awaiting a nice day without rain to mix and pour the concrete for the hearth. After that the fun part of building the actual oven component can begin!

[NCMan]

Thank you for the tips and advice!

In the inevitable event that the oven does get wet from rain or high winter humidity, do I just have to go through a drying procedure again? Say in preparation for first cook in spring after a long and wet winter.

It's always a good idea to slowly dry out an oven that has been sitting awhile, so yes. I wouldn't say you'd have to go through the whole original process, but it wouldn't hurt, especially w/your concerns/conditions.

[Pizzarotic]

do I just have to go through a drying procedure again?

Probably not that extreme. As you oven will be waterproof any water ingress will likely be in the floor insulation mainly. Run a fire for a day then close the oven and let it cool over a few days and you should be fine after that.

Nice job though

[JBA]

Building of the stand is underway!

I already have a concrete slab where I want the oven but decided to pour another 2-3" of reinforced concrete to make it level. On top of that I have dry stacked concrete blocks. Still need another angle iron - Lowe's only had one left near me.

Looking forward to pouring concrete into the blocks this weekend if weather permits.

[JBA]

Thank you for the tips and advice!

In the inevitable event that the oven does get wet from rain or high winter humidity, do I just have to go through a drying procedure again? Say in preparation for first cook in spring after a long and wet winter.

[Pizzarotic]

Since the plan is to leave the oven exposed, is it sufficient to drill weep holes into the hearth (or perhaps form them when casting?) and elevate the insulation using a layer of ceramic tiles?

That's always a good idea and will help dissipate any moisture that does get in.

I plan to also make all horizontal surfaces as water repellent as possible, such as painting the dome with several layers of waterproof paint and setting granite tiles around the outside perimeter of the dome.

Just remember, tiling is not waterproof as the water can still enter through the grout. Make sure you use a waterproof membrane under the tiles as well as the dome.

The part that would be left exposed is the fire brick that forms the gallery.

A outer door may help as well.

During the wet season here in Seattle and the Pacific Northwest I would try to keep the oven covered with a tarp.

Sounds like a good plan.

[JBA]

The oven will not be covered by a roof, at least not the way it is planned right now. Even if I added a roof, it wouldn't be possible to build something large with enough visual appeal to really protect the oven from rain when it is windy.

Since the plan is to leave the oven exposed, is it sufficient to drill weep holes into the hearth (or perhaps form them when casting?) and elevate the insulation using a layer of ceramic tiles?

I plan to also make all horizontal surfaces as water repellent as possible, such as painting the dome with several layers of waterproof paint and setting granite tiles around the outside perimeter of the dome.

The part that would be left exposed is the fire brick that forms the gallery.

During the wet season here in Seattle and the Pacific Northwest I would try to keep the oven covered with a tarp.

As for keeping the oven dry during building - I plan on keeping it covered with a tarp when I'm not working on it. Luckily, summers are reliably dry here in Seattle which also reduces the chance of accidentally leaving it uncovered in the rain when I plan to do most of the building.

Finally, when it comes to drying fires (or curing like people like to say), I'm already expecting that to be a 7+ day process regardless if the oven or floor will end up getting soaked or not.

[JRPizza]

Are you going to have some kind of cover to keep the persistent rain off the oven or are you going to try to waterproof it? I needed both a roof and sides on the South and West sides to keep the oven and hearth dry. If you are going to leave it exposed you should research all the means to keep the floor dry (weep holes and elevated insulation) and at least consider a temporary shelter to keep the insulation dry during your build. I soaked my floor early in my build and nearly a year later when I cured the oven I had to drive the remaining water out over several days of fires.

[david s]

After measuring the distance from the chimney to the nearest combustible structure (wooden deck), the distance is only 14".
Since NFPA mandates a minimum distance of 18" for single-wall chimneys, it looks like I will have to opt for a double-walled chimney.

I've done a few ovens through a roof, but now prefer an alternative solution that doesn't involve a double flue or penetrating the roof with its associated problems. There's not a great deal of price difference, but functionally I prefer the illustrated set up and don't mind the look. Check your local building code, but ours requires the pipe be at least 500mm clearance from the gutter and the flue exit 600mm higher. A couple of brackets are needed to secure the flue to the facia board.

[JBA]

After measuring the distance from the chimney to the nearest combustible structure (wooden deck), the distance is only 14".
Since NFPA mandates a minimum distance of 18" for single-wall chimneys, it looks like I will have to opt for a double-walled chimney.

[JBA]

Wow, thank you everyone for some great feedback, thoughts, and ideas! While I feel like I have a grip of the general steps of the build, there are many smaller but important details that I've been made aware of now. This will help me a lot in the coming months.


- The chimney will be about 20" away from the nearest wooden structure. From what I can gather, the clearance limit set by the National Fire Protection Agency is 18". I will take closer measurements later in my design to confirm.

- As for the dome insulation: I will keep the blanket at 3". The added vermicrete layer will primarily be to get the dome back in shape. I really like the two photos provided by Gulf and I will try to use a similar method to get a uniformly shaped dome. The vermicrete would then be finished with a render layer for a nicer texture, and finished with waterproof paint.

- Sounds like homebrew mortar is the way to go. If it saves me $100 then I'm fine with it being a little extra work than the pre-mix.

- Great tip regarding Harbison Walker in Kent! I will contact them about pricing for bricks and insulation. Really hope I can save a couple 100 there.

- I'll be upping the floor insulation to 4", hoping that well help the oven retain just that little extra bit of heat.

- Great advice again on how to design and build an oven door without requiring welding. I'll of course have an angle grinder, and have a nice heavy vice already to help me with the bending where needed.

- I hadn't considered heat loss mitigation around the gallery. I will reconsider my design and see if there's something I might be able to do there.


Really looking forward to building now that more and more of my conundrums seem to have good answers and approaches to them!