New Build on this side of the Pond

[underpendle]

Been Lurking in the shadows for a while now and thought it about time I got started and introduced myself, just in time for winter!!
Had a few days on my site prep and am almost ready for pouring my oven base. Don't have any real issues with the structural side of things but have zero experience of WFO's. Hope I don't disgrace myself on here and other users don't get too annoyed with what will be I'm sure a series of very basic questions.
Anyway so far removed about 10 Ton and theres no sign of the spoil heap getting any smaller, Waiting for some more stone to turn up and I can pour next series of footings.

Regards


Simon

[staestc]

Welcome to the forum! Looks like a nice corner for a WFO to me. I look forward to watching!

[underpendle]

Evening All.

Got some done this week and am hoping to pour oven base this weekend. Working sunday so going to be tight. I am thinking a little forward. I am planning on an ash shoot cast into the base. Not sure just how this will pan out but can always fill if required. Anyway, this will obviously require the smoke chamber being in the correct location. I have draw this out and come up with a minor concern which I hope one of you experts may help with?

I plan to build the front of the oven with a heat break and construct from Diatomaceous insulation bricks. Im a little concerned that my flue design may provide too much thermal mass. Hence the insulation bricks.

A little difficult I know without a proper drawing. will try and get a model done before I start building. but I hope build a brick flue, lined and insulated, arching back over the oven dome. If I insulate all well. do you envisage any probs?

For reference. I plan on 100mm CaSi under a 75mm hearth. 115mm firebrick wall, 50mm 128kg blanket over the dome, then vermicrete between this and outer brick. Will use insulating bricks, prob thermalite anywhere that isn't on show.

Recon on a 150mm flue, stainless liner insulated from outer brick with vermiculite and thermalite between flue and dome.

Thanks in advance

S

[underpendle]

A Late finish last night but got my base cast. A lot of head scratching to get my design to work in this location, what works on paper doesn't always fit!! Ended up sacking the idea of an ash shoot, occurred to me that this could make lighting harder, partic if you wanted to get flue warm first.
Tons of steel in a 150mm cantilevered base, troweled up fine this morning. I'll give a few days to cure before removing the forms. Tons of work to go into rest of site anyway. Just for interest made with strong mix, 150Kg of cement in that!! Reinforced with two layers of A grade mesh, A piece of Box Section to assist with the Cantilever and 20mm ReBar.

[jonv]

Interesting base! I'm most curious... what have you got planned for that space underneath that makes supporting walls inconvenient? I haven't seen one without more support underneath - going to be quite a weight when finished - where does the steel run?

[underpendle]

Not really sure what I'll do underneath, but wanted to keep my options open, Don't really want the area to cluttered so may just leave open. I'll make my mind up when its nearer completion. Steel is a lattice Box running cross corners then heavy rebars front to back and across. Two layers a A142 holding that lot in place. Ive also anchored to both walls. Not concerned about the weight, most is at the outsides and I plan on sweeping the flue back over the top again throwing weight to the rear. When completed I intend to build a hipped roof over this area using the flue as part of the roof construction and hence also adding more weight to the cantilever. Fingers crossed Ive worked it all out ok otherwise I'll have to get the big hammer out!!!

[Gulf]

I may be missing something. But, I don't see where the slab extends back over and beyond the block walls to make it a cantilever. Be careful, and don't let the kids play under there. What is A142?

[underpendle]

Thanks for your concern. Im sure/hope it will become obvious as the build continues. The cantilever has been formed internally. the effective unsupported section being 500mm and the supported 1300mm. this will then be incorporated in the rest of the masonry/Roof structure and hence be supported. I have made my staircase along a similar line casting individual steps out of concrete and then polishing them, in this case the additional weight required has been supplied by the upstairs floor and ultimately the roof.

A142 is a grade of remesh I use in floors.

Cheers S

[jonv]

A142 is a 6mm mesh - I used some on my slab along with 12mm rebar.

[fnbroken]

Watching with interest - a drawing of how you have done this would be great for understanding the principles...

I wouldn't be crawling around under there either!!

[jonv]

You are braver than me - I would have nightmares about that weight hanging around... I hope it works out for you.

[deejayoh]

Looking at the pictures - it's not really cantilevered if it is supported in the corner by the two walls. Seems like it's more of a cast span. If the oven is toward the back it's weight is supported by the walls. That said, it's a pretty broad span. The steel will need to do a lot of the work.

[underpendle]

Thats why I cast it 150mm thick and put a lot of steel in. I'm not concerned. Good job really just spent the last couple of hours stood on it sorting out that back wall.
I would agree with DeeJay. mostly a span but would call the front a cantilever. Doesn't really matter if it works. 1800mm at its widest, with 20mm ReBars, I'm confident it'll be fine. Don't think it would get a comment if it was a precast 150x100 lintel I've also cast a piece of 40x40 box in, really cos I had a piece kicking about. Time will tell.


On a completely different subject. I'm about to order fire brick etc. I have asked this elsewhere but can anyone offer advice on the relative pros and cons of running the hearth under the inner brick wall. I can see that you wouldn't be able to get them out in the event of a breakage but think that unlikely. Planning on 100mm CaSi under the hearth and provided the external insulation passes below the hearth I can't see any disadvantage from an insulation point of view.

Just thinking the overall finish will be neater with the wall built on the hearth.

Had thought 50mm blanket on the outside, but think I may up that. I can a double to 100mm or add a layer of Tri-iso super10. But not sure what the temp likely to be at that point.?( Tri iso is a high grade multi layered ins used in UK, but NOT fire resistant.) Think the Tri iso will have a superior U Value. I think I will be adding a layer of Vermicrete as well to aid construction when I come build the external skin.


Any thoughts

S

[deejayoh]

Bricks under the dome wall is fine. I've never seen anyone have to replace the floor bricks. If you did, they'd more likely be in the middle than on the edges.

As to insulation, I would go with 75-100mm on the outside. 50mm is a bit skinny.

[jonv]

I'm only just starting my own build so I might have misunderstood many things, but I thought some folk cut the floor bricks to fit inside the dome, with a little bit of a gap, to allow for expansion of the floor? That's my plan, anyway, although there seem to be plenty of builds with the dome sat on the floor bricks - haven't read of any problems with this...