Please help! Wooden wedges

Hi, I used a set of wooden wedges to prop up each bricks while building my oven. Unfortunately, I forgot to remove them and mortared the gaps with the wooden wedges still between the bricks. I am about halfway done and the mortar has set hard. As anyone else done this? I suspect the wedges will burn when I fire up the oven and create some issues down the line. Do you have any suggestions? Thoughts?

Much appreciated

Joel

Hi Joel!

Sounds like you’re making good progress on your oven, even if you’ve built a little something extra into the mortar.

I think you’re right. Theoretically they would be in a sealed space if your stucco shell is perfect, thus denying oxygen to the wood as it heats up. Nevertheless, the mortar and firebrick are your primary lining for the oven, and having a combustible material in place of the refractory mortar is not a good thing. The closest reference I could find is to chimney construction, where a double course of bricks and a fire-clay lining are required and nothing combustible is allowed within two inches of the chimney.

Are the wedges accessible? (That is, do their faces still come out to the surface of your joints?) If so, I’d recommend starting with a masonry chisel and a hammer (you’d kill a woodworking chisel and you don’t need the precision) to dig out as much of the wedges as you can, then a shop vac to suck out all the debris and dust. You may be able to remove all of it using just these tools, or pretty close. Then, mix up another batch of refractory mortar and point it into the gaps left where the wedges were. Remember to mist those gaps with water before you add any mortar! You want the new mortar to have the best chance of adhering to your existing work.

That’s going to set you back a few days, but it’s definitely not worth it to just leave them in there and hope for the best.

Good luck, Joel, and keep in touch!

Hi Matt,

Thanks for the reply and advice. The wedges are literally between bricks buried deep in mortar, which were set hard as of your reply. I tried to chisel them out but impossible. The mortar is way too hard at this point. I dont have choice but to hope for the best at this stage. One thing I was considering doing if to start curing before covering the dome with insulation and completing the build.

Will keep you posted

Thanks again

Joel

If they are completely encased, probably best not to worry about them. (That’s the case I didn’t address in my first response.) I also wouldn’t worry about curing before you insulate. In general, because they are embedded and not exposed outside the mortar, don’t worry.

The mortar itself is refractory, and should provide enough “protection” to keep the wood from smoldering or combusting. Without oxygen, it’s just not a happening thing.

In a thousand years, when archaeologists of the far future examine this amazing enduring structure, they’ll take samples of the mortar and discover ancient organic fiber embedded in it. So you’re contributing to history!