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Food With Legs 05-03-2010 11:00 AM

Island Pompeii 42" in Ontario
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After a long time of talking about I (with a lot of help from family) have finally broken ground on a wood-fired oven project. We'll be using the excellent Pompeii 42" plans.

As I mentioned in my introduction post we are facing some interesting challenges with this build. First, we're on an island northeast of Toronto, Ontario so materials have to be brought in by boat and all concrete will have to be mixed by hand. Secondly, our site sits on very little topsoil (2 - 4") and then levels of fairly solid limestone sandwiched between smaller layers of clay (see the first picture).

To give some extra weight distribution and provide support for finishing the outside of the block stand we dug a footprint bigger than recommended (ours is 79" X 92") and 15" deep. The next layer is six inches of solid dolomite limestone on top of clay and the frost line is somewhere in that six inches.

Our plan is to dig four piers (8" dia sonotube filled and reinforced with rebar) twelve inches deep (i.e. through the six of limestone and six of clay below it) and roughly under the eventual corners of the block stand (so in from the corners of the foundation pad. We'll then fill with gravel and pour a 4" slab tied into the piers. In other words we'll have 4 inches of slab supported by about 24 inches of pier in some places and 4 inches of slab on about 12-13" of gravel on dolomite in others.

Is there anything wrong with this plan? Should we tie the piers together laterally with poured grade beams? Should we used extruded foam board between the slab and gravel, at the bottom of the piers, or at the bottom of the grade beams?

Sorry to make my second post such a long one with so many questions but as you can probably tell I'm eager to get building. Thanks in advance for any help.


John D. Burke 05-14-2010 07:32 AM

Re: Island Pompeii 42" in Ontario
David -

Looks like you have really engineered your plan. My only concern would be turning a floating pad into a fixed pad with the sonotube piers. Might this lead to cracking? I don't know the answer but our Canadian winters can be pretty brutal.
I'm just starting to build in Iroquois Ontario - about 400 kms. east of you - and opted for a six inch packed gravel base with 5-1/2 inch steel reinforced concrete that will sit about 1-1/2 inches above our swimming pool deck when it's finished. It's a way to go before I need insulating materials but I would appreciate any sources you have found for the ceramic fibre board base and blanket insulation for the dome.



Food With Legs 05-31-2010 09:11 AM

Re: Island Pompeii 42" in Ontario

On the recommendation of CanuckJim we have been sourcing materials from Alphatherm in Markham, ON. Apparently, they get 5-7 backyard oven builders a week so they seem to be an alright source of expertise.

We got mortar, firebricks and fibre board insulation from them and plan to go back there for more firebricks and the blanket insulation. On the salesman's recommendation we decided to go with the K-Fac 19 board insulation. It gets some criticism on the forum, I believe, because it is not rated for bearing weight in industrial situations. I'm confident that it will be fine for the oven but make your decision based on a forum search etc.

All part of the improvisation needed for those of us living outside the range of reasonably-priced shipping for the FB materials.


Food With Legs 05-31-2010 09:36 AM

Re: Island Pompeii 42" in Ontario
4 Attachment(s)
Our project is progressing nicely--especially considering we're only there on weekends and it's boat access only.

I think we have solved the question of how to build a frost-secure foundation in our unique circumstances. As a hybrid between the recommended

-dug a rectangular hole fifteen inches deep to solid rock.
-in the four corners, using a cement saw and jackhammer, dug a further twelve inches down.
-set reinforced piers--eight-inch sonotube with three pieces of 1/2" rebar--in the deep corner holes
-connected the piers with reinforced concrete grade beams
-backfilled with crushed rock to grade outside the beams and within a couple inches of the bottom of the pad inside the beams
-placed the blue SM insulation between the crushed rock and what would be the bottom of the pad and also around the sides and underneath the grade beams

I am not an expert on building foundations but based on what I have read here and the expertise from those who have done this sort of work for heated and unheated buildings in our area I think this a good solution to our situation. Again the unique characteristics are an area that experiences very cold winters (-18C is not uncommon), has a high water table, and very little topsoil before the much more difficult to excavate rock starts.

Attached are a few of photos of the foundation.

Food With Legs 06-09-2010 06:54 AM

Re: Island Pompeii 42" in Ontario
3 Attachment(s)
I know I haven't been great about updates but here's another one.

The foundation slab has been poured. Concrete blocks dry-stacked, leveled with mortar, and every second core filled with rebar and more concrete. We're now working on forming up the hearth slab that sits on top of the block stand.

Two lessons learned:
1. We struggled for a while with the layout of the blocks for the stand but then just decided to simplify, shrink it a bit and will have our hearth slab (for a 42" oven) overhang its sides. We only used two half blocks, either side of the door in the second course.
2. Notched a small channel in the top of the first course of blocks and laid rebar parallel to the ground into this channel. Don't know how vital this is but the hope is that if anything shifts it will happen evenly.

I have two planning ahead type questions:
1. We have decided to span the two openings to our oven (door before vent and door into dome) with angle iron supported brick instead of arches. What size angle iron should we use? Pg. 41 of the Pompeii plans calls for 2"X2"X3/16" but the materials list on pg. 67 calls for 1.25"X1.25" (thickness not specified).
2. Because our build site is weekends only we like to get as much done as possible when we're there. When setting the bricks for the dome is there a recommended max number of courses that can be set in one day?



dmun 06-09-2010 08:16 AM

Re: Island Pompeii 42" in Ontario
You can do the first four courses all at once, because most of the forces are downward, and there is a minimum of trimming, if you're keeping the mortar triangles minimized. After that it slows down, because the forces are more inward, and the bricks tend to fall in.

John D. Burke 06-09-2010 10:14 AM

Re: Island Pompeii 42" in Ontario
David -

Looks like you're making great progress. You're one step ahead of me by pouring your platform already! That's my task this weekend.

Thanks for the advice on contacting Alphatherm north of Toronto. I ordered everything by phone and a 1,700 pound skid of materials arrived in Ottawa within two days.

Keep posting


Food With Legs 06-10-2010 06:22 AM

Re: Island Pompeii 42" in Ontario
Thanks, dmun. I suppose a really good indispensable tool like jcg31's clamp-equipped masterpiece helps? Time for me to head into HD/Lowes/Rona with a blank look and some print-offs.

Thanks for the encouragement, John. With the volume that Alphatherm apparently does seems like they would be a good distribution partner for FB here in Canada.


Food With Legs 06-29-2010 06:53 AM

Re: Island Pompeii 42" in Ontario
2 Attachment(s)
Time for another update...

Turns out that my cousin and one of our neighbours has an arc welder so the Indispensable Tool came together more easily than I expected. We cut down an old, adjustable square to use as a brick guide and included a turnbuckle so that the tool's length is adjustable.

With lots of family help we poured the hearth slab last weekend. One thing we did that I haven't seen much of is that we set a length of synthetic rope around the perimeter of the form, about a 1/2" in from the sides. The idea here is that it will create a lip on the underside of the slab's overhang that will encourage rain to fall straight down instead of running down the walls of the block stand.

Food With Legs 06-29-2010 07:04 AM

Re: Island Pompeii 42" in Ontario
1 Attachment(s)
So, moving forward I have two questions:

First, and here I am expecting a "you're over-thinking things" reply or two, I have started to lay out the floor bricks and I'm wondering about the herringbone pattern. I notice that a large but not overwhelming majority lay their pattern left to right (i.e. the fish's backbone would go in this direction) but I have laid mine front to back. See the attached photo for my way.

Does it matter? Anyone laid it front to back and wish they had done it the other way?

Secondly, I'm wondering about connecting the walls of the vent support/entryway to those bricks at both corners of the inner door. We're doing a straight-across, bricks-and-angle-iron inner door lintel and a clay flue tile on a fabricated metal vent.

How important is it to avoid a running mortar joint at this spot? I'm having trouble wrapping my head around how to vary the bricks from course to course and still incorporate the 1" reveal, etc. Would appreciate a pointer to anyone's build who has done this smoothly.


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