My pizza oven exploded!!!

[Dave T]

I have an FB Casa2G100 40 inch oven, installed in a massive granite monolith with a fireplace below:




It was installed about a year ago. Since then, I've had about 15 pizza cooks, but I've never used the fireplace below until last night, after cooking some pizzas. I had a decent fire going for an hour or two, when suddenly the oven exploded. It was pretty dramatic. There was a loud boom, and a lot of concrete fell from above into the fire in the fireplace, and it blew the fire bricks upward in the pizza oven above. What exploded was the level between the floor of the pizza oven, and the ceiling of the fireplace. My wife talked to the contractor who installed it, and he said he thought they'd used the wrong kind of mortar. I have a call into him and haven't talked to him yet. He says they're make it right, but clearly they didn't do a good job, and I want to make sure that they fix it correctly this time. Can anyone here please advise me as to what I should ask/tell them?

I'm attaching some pictures. I'm having problems figuring out how to pretty up this post, hopefully you can make sense of these pics.

Thanks!

Inside pizza oven, showing firebrick floor displaced by the explosion:



Another view inside oven:




Looking up at underside of pizza oven, from inside the fireplace:

[JRPizza]

Dave, sorry to hear about your explosion! You need to repost your pictures though, nothing shows up when I click on the link. It will be good for the forum to follow your investigation into this failure. I have seen quite a few posts from builders wanting to incorporate a fireplace into the oven build - you misfortune could offer invaluable lessons as to what to avoid when putting the fireplace below the oven.

[david s]

Without being able to see the pic the first thing that comes to mind is moisture sealed in the insulation layer under the pizza oven floor bricks, turning to steam suddenly from the fire below it. What kind of insulation was used in that layer? Perhaps you should be directing your problem to Forno Bravo as this may be a warranty issue.

[Dave T]

Ok, I got the pictures up, kinda. I am having problems with the site - when I go to add the pictures and save my edit, it just sits there forever (I waited about 15 minutes), saying "Waiting". Then if I cancel the upload, the pictures seem to be there.

Anyway, any suggestions about what I should discuss with the contractor who installed it? Let me know if you need to see anything else.

[JRPizza]

Don't add them as an edit - there has been a problem with the edit function for some time. Try making a new post in this thread and see if you have more luck.

[Dave T]

I did add them as an edit. I had started the thread and tried to exit out and delete the post, but it wouldn't let me delete so I had to edit the original to avoid having two threads.

It looks good enough now, see above. I'm also not getting notifications of new posts to this thread. Is that supposed to work?

[JRPizza]

Not sure what is going on then - still blank above. Also when I go to your profile and look at your media, I see 6 photos of your oven, 2 you posted back in 2015 and 4 from March of this year.
Anybody else see Dave's newest pics?

[Dave T]

Can you try refreshing the page? I checked on two different computers as well as my phone and I see the pictures everywhere.

[Gulf]

Dave,

I can't see them either. Are you using the camera icon or the attach image icon. If you haven't tried both try, the other. Also, when posting or editing a post, previewing first seems to upload better.

[JRPizza]

Thanks Joe - I refreshed, cleared my cache, and rebooted with no luck. Even tried out desktop computer and same results - no pics.

[Caliea]

I don't see them either

[Dave T]

I used attach image. They're definitely there, embedded in the first post. I had uploaded them from one computer, and then was able to see them on a different computer as well as my phone. I guess it's some kind of bug in the site.

I am attaching the pics again here, in this post. Thanks for the help!

And update - I just talked to the contractor. He was embarrassed, and said his guys had used the wrong kind of mortar for the bottom of the floor. He said they will fix it by building a platform and pouring the right kind of mortar on, supported by a grid of rebar. They will replace the insulation and firebrick. Anything else I should ask him or tell him?

[Gulf]

I can click on the attached files and open up the pics in your last post. Daammnn! That was a heck of an explosion. I'm going to agree with David on this. It must have been trapped steam. Something had to be present and trapped that violently expanded to have caused that. Since this is not a gas fired oven, steam trapped between the roof of the fireplace and the floor of the oven is most probably the culprit. I have more to add but, I have supper to attend to at the moment.

[Dave T]

Hmmm. I think steam would have been able to escape through the cracks in the firebrick. Do you know about using the wrong type of mortar in a high heat situation? Apparently, it can explode, which is what happened here, so I'm inclined to believe that.

[Gulf]

And update - I just talked to the contractor. He was embarrassed, and said his guys had used the wrong kind of mortar for the bottom of the floor. He said they will fix it by building a platform and pouring the right kind of mortar on, supported by a grid of rebar. They will replace the insulation and firebrick. Anything else I should ask him or tell him?

I'm thinking that there should have been a refractory brick lining the sides and throat of your fireplace. Insulation or space between that and a reinforced concrete hearth. Then more insulation and finally your oven. Placing a properly functioning fireplace directly under a wfo (in that amount of space) is above my paygrade. Perhaps, it is above your contractor's as well. I think that it would have to be a mortar that I have never heard of to do that alone. But, since your contractor is on track with it, let him warranty it on that basis. The oven has to be removed from the base to make these repairs. Placing a fireplace under a wfo is an extreme build. Make sure that there is all the components mentioned above and that there is some form of venting for that area between the two.

just sayin'