Question about ground insulation (cross post from Pompeii ovens)

[uneekwahn]

G'day guys, another Aussie here.

I've posted this here and the Pompeii oven forum hope this isn't a problem.

I'm looking at building a WFO in my backyard. I have just had a limestone retaining wall built, and as my property is tiered, I have the ability to have the floor of the pizza oven on the highest level, meaning I don't need to build an actual base.

Here are some photos.

In this first photo, the area where the oven will go is (unfortunately) directly behind the post.



In this photo, you can see the area a bit clearer.



And finally, the area where the oven will go. Basically right in the corner.



After today's effort of bitumen sealing the back of the wall, next weekend will be backfilling the area and then having it paved the following week.

There will be a 1.5m2 (about 5'2 - not sure how to symbolise feet squared?) left of plain, clean sand. This is where I plan to build the oven.

I plan on making a concrete foundation and am wondering whether I need to lay insulation below this? Could I put some form of insulation material into the concrete? Would I even need to worry about insulation?

Look forward to hearing people's thoughts.

Cheers,

Jason.

[Lburou]

Re: Question about ground insulation (cross post from Pompeii ovens)

It looks like you have a good location Jason

I don't see any value added to insulatiing underneath the slab. If you insulate as depicted in the pompeii oven plans, the insulation will be on top of the hearth slab and the oven on top of that.

Looking at your retaining wall, I'm sure the wall will hold the part of the oven resting on it....What I have a question about is the backside of the oven.....? Without a footing and blocks to support the back side of the oven, it will certainly settle and that will compromise the hearth slab for level and who knows what else. Are you planning some kind of support (roughly equal to the wall support) for the back side of the hearth slab?

Best regards,

[uneekwahn]

Re: Question about ground insulation (cross post from Pompeii ovens)

Hi guys, many thanks for the responses.

I hadn't given any thought to laying some form of foundations at the back before laying the slab. The guys laying the pavers will be compacting the area prior to paving, and I was hoping that that would be sufficient enough.

Regarding the limestone wall and whether it would take the additional weight, the oven won't be on the wall directly, but butted up to it.

Here is my dodgy drawing of what it would look like from the side.



My father was once a construction and maintenance manager for a reputable home building company a number of years ago and he believes that compaction of the soil by the brick pavers would be sufficient. He hasn't done this for a long time, and I am definitely happy to take on board what others here are saying due to your experiences.

Cheers,

Jason.

[BOOMERS WFO]

Re: Question about ground insulation (cross post from Pompeii ovens)

Hi Jason,

My concern would be where the water runnoff goes from the upper area? I assume it will be paved and does not look like it will be under the verandah. Last thing you would want is a waterlogged oven. Also, the height would be ideal for kids to climb over etc. Not perhaps good if oven ( and flue) are hot!!!

Cheers

Craig

[Gulf]

Re: Question about ground insulation (cross post from Pompeii ovens)

What ever you do, make sure that all areas of the foundation are treated in the same manner. Front back and sides should all have the same settling rate. Dig down on the back and sides and mimic what was done with your retaining wall. You can tie all of these together with a thick reinforced hearth. Put your moisture barrier either between your retainer walls and the hearth or directly on top of the hearth (between the hearth and insulation).
Since you will not have a wood storage area, this would be the best way to stop the moisture wicking problem. Failure to do this might mean retrofitting French Drains. Trust me, you don't want to do that .