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Serious trouble with my vent design. Please help. - Forno Bravo Forum: The Wood-Fired Oven Community


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Serious trouble with my vent design. Please help.

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  • Serious trouble with my vent design. Please help.

    A little dramatic but I hit a huge road block here.

    I have decided to abandon the idea of a metal vent and I'm going with clay. I have posted some one else's picture and his build is here: https://community.fornobravo.com/for...sic-oven?t=765


    1) how did he link the flue liner pieces together or how should I?

    2) around this flue I'm going to use fire brick. What do you put between the fire brick and flue liner?

    3) this oven is uncovered and beside the ocean and in a rain forrest. Does mean I should cover the whole thng with quickwall to waterproof it? This will take away the asthetic appeal but I could alway do sheets of tile after like in a restaurant.

    4) how tall do I need to go with the chimney? I was planning on 60" total length with 8x8 square clay flue liner.

    I believe I have build a 38" oven with the proper 63% entrance way.

    Thanks everyone

    Here is my build so far:


  • #2
    Do you have a wet saw?
    Joe Watson, "A year from now, you will have wished that you had started today"
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    • #3
      1) I used a similar design for my oven's vent system. I have an old blog post that shows how I cut the lower sections of flue pipe & fit them together. My build here doesn't cover it very well but it also might help. Here's the link to the blog post (and the link to my build is in my signature line);


      2) I used a homebrew mortar to bind the two pieces together and held them together with some nylon line until I put the top piece on with more mortar. I actually used nested liners and created a facade of brick on the outside of the flue. My dome's upper insulation has an "open" pathway to the gap between the liners. I put this in play with the idea of providing a vent for any moisture that might build up and need release. You want to make sure your flue pipe has a little room or flexibility for expansion as it heats up. I used fiberglass wood stove gasket rope placed in a couple rings around the flue for mine.

      3) It sounds to me like you might seriously consider putting a structure over the oven. Waterproofing additives are available for render on the outside, but they do need fairly constant attention/maintenance in the kinds of weather you have. If you do keep the outside (no building cover) approach, I'd advise putting a layer of foamglas between the hearth and ceramic board insulation (your dome & cooking floor would rest on top of the ceramic board). Ceramic board will wick moisture in from around the edges (where cracks normally occur)...the foamglas does not wick water and protects your oven from getting a "wet floor".

      4) The height of the chimney will be more to get the smoke above the heads of your guests and you. That height is great but the 8 x 8 size is probably ID and you'll be really having just an internal 6 x 6 opening. I have a 39" oven and used 8 x 8 (OD ) flue pipe...it works, but I do get a bit more smoke than I want. If you can go up to the next size of flue pipe, I think you'll be happier...

      Hope that helps a bit...p.s. I'm quite spatially challenged, so cutting the flue pipe sections was a real adventure (and I had sacrificed a flue section figuring out how poor my skills are using a grinder/masonry blade and/or a masonry blade in my skilsaw)
      Last edited by SableSprings; 06-09-2018, 06:10 PM.
      Mike Stansbury - The Traveling Loafer
      Roseburg, Oregon

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      • #4
        If you have pulled a permit and are getting inspected your height needs to be 3 ft above the roof, assuming an enclosure. Here's the relevant code:

        1001.5 Termination. Chimneys shall extend at least 2 feet (610 mm) higher than any portion of the building within 10 feet (3048 mm), but shall not be less than 3 feet (914 mm) above the point where the chimney passes through the roof.
        My build thread: https://tinyurl.com/y8bx7hbd


        • #5
          Thanks everyone. I ended up doing a combination of things. I built a funnel which ended at a masonary anchor. Then I went for a stainless steel vent. I can take it off when Iím not using it which will be helpful.


          • #6
            Originally posted by ubcpsyc View Post

            3) this oven is uncovered and beside the ocean and in a rain forrest. Does mean I should cover the whole thng with quickwall to waterproof it? This will take away the asthetic appeal but I could alway do sheets of tile after like in a restaurant.
            As someone who shares a climate with you - but perhaps a bit drier (Seattle)... I'd recommend against an igloo. Neither stucco or tile is waterproof. Even if you can keep the dome dry, water can still seep in around the base. Nothing worse than a wet oven.
            My build progress
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            • #7
              Wow your oven is gorgeous!

              i agree that on the north west coast we should all be building our ovens with some sort of enclosure. Unfortunately my oven sits out on a high bank peninsula exposed to high winds and it is too small an area to build an enclosure. That stainless steel chimney is on a masonry anchor so I can take it off and cover it with a tarp when Iím not using it. Luckily there are no sight lines to the oven from our deck so it wonít be an eye sore when itís covered.


              • #8
                Thanks. You've got quite the spot there for yours...
                At a minimum, I'd make certain to slope everything away from the base of the oven so that water won't pool. It can wick in through concrete over quite some distance if allowed to pool
                My build progress
                My WFO Journal on Facebook
                My dome spreadsheet calculator


                • #9
                  Thatís great advice. Iíve already noticed that. As a temporizing measure I applied the quikwall right down to the countertop and sealed the whole thing and the junction with acrylic sealer. It will still have to be covered when it rains of course.


                  • #10
                    It will be interesting to see what kind of a cover you come up with - please share. We spent a winter using temporary cover over our dome and it seriously put a damper (pun intended) on cooking, and a few times I went outside to see that the wind had blown up one side of my cover and water had leaked in. The second year we had a roof but no sides, and had similar problems when the rain was coming in horizontally. We had temporary sides but they had trouble battling some of our higher winds. We ended up with a roof and two sides guarding against the prevailing winter winds (South & South West) and that has kept the oven dry and allowed for year round cooking.
                    My build thread