Ovem build on a soil bank?

[ross]

Hello, this is my first poat here, i have read lots of material (books and websites/forums) about building wood fired ovens, though i have a question i am hoping someone can amswer. Is it sensible to build a woos fired oven on a raised soil bank? I have a high bank surrounding my patio that would be the perfect height to build an oven. If i were to put a concrete slab ontop of this bank and build the oven on the slab? Has anyone done this? Would the weight of the oven cause the bank to colllapse? The bank has been there flr years and is wrll.compacted amd full of plants so plenry of roots etc.

Any advice would be appreciated!

Ross.

[truckcab79]

I imagine it would be fine, but difficult to be sure without seeing it. Personally if I was happy that it was as firm and compacted as you say then I'd go for it, but add a strong rebar frame into the slab and link it down into the bank with vertical rebar to give it more stability. Probably overkill but peace of mind, and you can't go back and do it later.

[oblertone]

As above, you need assurance that your slab won't decide to visit your garden at some later date, so excavate and shutter your slab but before pouring hammer some vertical rebar stakes into the ground to 'peg' your slab in place.

[ross]

Thanks for your replies, i was fairly confident it would be ok, but i think to add a little extra support (along with the rebar stakes & reinforced base), i might built a small retaining wall at the front. i am thinking of placing the front edge of the slab on top of the wall to aid support, or could this be a mistake? if the soil does compress a little, it may put extra force on the base with it being tilted instead of just 'settling' (at least if that does happen, i hope it would be just a small amount of settling!).

i was also thinking of making the base wider than required, to help spread the load, and then back filling the edges with soil to keep the misses happy!

i was thinking something like this:

[devontiger]

ross, how about a couple of pictures, so we can judge the wall.
Very hard to say one way or other without Pictures.

But I must admit it does sound good.
DT

[ross]

thanks for the reply, i have taken a photo now, and here it is:





and here i have added my intentions:




does this help make it clearer? i know with the plants its not as easy to see, but its a very solid bank (trust me, ive had to dig plants into other areas of it!).

P.S., Ignore the Gnome, i found it buried in the flowers (I have only lived here a year)!

Ross.

[downunderdave]

Jun 25, 2018 10:50:46 GMT ross said:

Thanks for your replies, i was fairly confident it would be ok, but i think to add a little extra support (along with the rebar stakes & reinforced base), i might built a small retaining wall at the front. i am thinking of placing the front edge of the slab on top of the wall to aid support, or could this be a mistake? if the soil does compress a little, it may put extra force on the base with it being tilted instead of just 'settling' (at least if that does happen, i hope it would be just a small amount of settling!).

i was also thinking of making the base wider than required, to help spread the load, and then back filling the edges with soil to keep the misses happy!

i was thinking something like this:

I think you’re asking for trouble if you build it according to your pic. The oven should not have soil surrounding it or moisture will migrate into your oven, wetting it’s insulation  which will require you to be constantly drying it. Try to make sure that at least the insulation is well above ground level. If it were mine i’d Be digging some footings and so also have the supporting slab above ground level. Water fairly easily wicks up from the base into the underfloor insulation for ovens without a stand.

[ross]

this was a concern as well, i am trying to think of a solution. perhaps if surrounded the base with damp proofing? i am not a builder as you can tell i am sure. how about building the base slab (with damp proofing) on top of the soil?

[devontiger]

ross, I would look for another position, or remove part of the wall, & build a proper base.

[ross]

there isnt really a better place, or any other place to be honest, and i would rather not dig out the bank as its quite close to my house. i think i may just raise up the slab and surround it with Damp proof Membrane, i'm sure that should give it the same chance as any free-standing oven surely? as long as the second slab is well insulated, the heat shouldn't damage the damp proofing i would imagine. any one have any experience with damp proof membrane?

also, just a question, when building an oven with a full base/stand, is the base slab surrounded by DPM? if not, whats to stop the moisture rising through the base/stand? is it simply the distance it would have to travel to reach the top of the stand?

[downunderdave]

Jun 25, 2018 22:08:40 GMT ross said:

there isnt really a better place, or any other place to be honest, and i would rather not dig out the bank as its quite close to my house. i think i may just raise up the slab and surround it with Damp proof Membrane, i'm sure that should give it the same chance as any free-standing oven surely? as long as the second slab is well insulated, the heat shouldn't damage the damp proofing i would imagine. any one have any experience with damp proof membrane?

also, just a question, when building an oven with a full base/stand, is the base slab surrounded by DPM? if not, whats to stop the moisture rising through the base/stand? is it simply the distance it would have to travel to reach the top of the stand?

I put plastic under the foundation slab and although it would prevent some rising damp, acts more to retain moisture in the concrete when laid while it cures to get more strength. In order to reduce moisture wicking up the stand, I like to make the foundation slab higher than the surrounding soil level. The higher the stand the less moisture will be wicked up. I also put in an additive (Xypex) when casting the supporting slab which makes the concrete waterproof, as well as coating the top of the stand supports with sealer. Not really sure how much all this helps, but it must be better than not doing anything.

[ross]

I think if i line the slab with damp proofing, add the additive to the concrete mix to make it waterproof, and then seal the top with another waterproofing sealant and built the insulated base on top of that, it might be ok... and if not, i'll have to try something else! if i do the slab and leave it a month or so, i should be able to tell if its waterproof or not, shouldn't I?

thank you for you advice, i did not realise concrete was so porous until you guys mentioned it and did a little more research.

[truckcab79]

I'd be incline to dig out a bit, build strip foundation, then concrete slab set on that. You could have it low so it's barely above, but not touching soil level, giving similar effect to your first suggestion.

[oblertone]

Just to add another factor to the mix; your oven floor should be at elbow height for the main user, otherwise you'll be stooping a lot. That might give you some idea of how much slab you'll need t cast.

[ross]

the height is a good point, i will need to measure, but actually, i may have to build a small base, say 1 level or concrete bricks, perhaps 2 to get it to the correct height (with digging down for foundations). so actually, it may work! i will have a measure up later. thanks for the help everyone, i appreciate it.

also, i just noticed that a number of you chaps seem to be from Devon, im in Plymouth, so another devonian!