Planning next phase & needing help

[waynebergman]

The lid came out nicely without sticking and all looks good. Showing pictures of rock I got at the beach yesterday that I plan to face the upper section of dome suround. Also shown is rock and slate propped up kind of like I plan to place them. Planing now to not do the igloo look with the stucco but rather a round enclosure (similar in diamiter to stand but about 3 feet height) containing the insulation around and on top of the oven and it will also serve as a structural wall to hold up the roof. Would like some feedback on my plans for this as I am a bit unsure of a few things. I was thinking of getting a large piece of reinforcing mesh 3' by 18' and making a big 68" diameter by 36" stucture to place around the oven to act as a guide and holder for mortar and rock to rest against. Thought if I got some masons mortar and added a bit of portland cement to it and applied it like a 2 inch cladding to this mesh and then after it set up mortar my rocks to it. Then this would be my walls for the roof. Sorry I see the middle attachment is the wrong one. Some things I am not so sure about are....

How much cement should I add to the mortar?
Will it be strong and hold out our Canadian winters?(more rain here than snow)
What kind of mesh would be best suited for the job?

[Frances]

A round oven covered with pebbles . Sounds like a cool idea, I like it.

From a bit of experience with cement-based sculptures, I think it should be doable. Could you include some rebar in the wire mesh structure? Say bore some holes in the hearth and place vertical rebar lengths in them? I would also suggest a second layer of wire mesh inside the cladding - clad the first lot of mesh in 1 inch of mortar, wrap the second layer of mesh round it and mash the final inch of cladding over it. I use the wire mesh with hexagonal holes which is used for rabit hutches for my stuff, and it holds up fine.

I don't know If you need any more cement in the mortar - the stuff they sell here is fine without, but of course it may be different where you are.

What kind of roof are you planning?

Hope this helps,
Frances

[CanuckJim]

Wayne,

Frances has got the superstructure nailed, so no need for me to comment. Using rebar is a must. You could either use rabbit hutch wire or wire lath, which might be a bit stronger in the end. Or hutch wire for one layer, lath wire for the second. Frankly, I'd go a bit thicker than two inches to bear the weight of the stones. For the mortar, I'd use Type N and brick sand (3 sand to 1 mortar). Type N is very good for vertical surfaces that will be exposed to rain. You don't need to add Portland to it, although a bit of accelerant (Home Depot) will help the mortar set up more quickly in cold and wet weather. Be sure to tarp your work between sessions.

Jim

[waynebergman]

First to answer your question about the roof, I am not sure yet. I am thinking kind of a mushroom cap look to the roof. Maybee copper or Cedar.Would like it to be suported by the walls here that you are helping me with. The roof will just hang over a bit from the walls, maybee a foot or so. Still a few things I am not so sure about.....

Type N mortar I think is one part cement 1 1/4 lime and 6 or so sand, so a little confused Jim about the 3 to one you mentioned. Should I take the above formula for type N mortar mix that and then add sand at 3 to one? Sounds like too much sand but maybee I am not understanding you right.

If I drill through the hearth for the vertical rebar I will be going through about 4" of the vermiculite concrete before I hit the stuctural concrete. Any issues here? Is this vermiculite conrete got any strength or should I drill out an extra big hole and then mortar the rebar in place?

Thanks again this has been a big help.....wayne

[CanuckJim]

Wayne,

Apologies; I was a bit sketchy about what you planned. Nope, Type N mortar has no sand in it at all; it's not a mix but a pure cementitious product. You can buy it at HD, and the bag will be marked that way, like Type S and Portland bags are. Just use one part Type N to three parts brick sand. Type N is normally used for pointing, parging or exposed exterior layers. You might want to pour the interior walls (around the rebar and mesh) with ready mix Sakrete (stronger because of the included aggregate), then parge the outside of it with Type N, then use it again for a bed in which to secure your stones. Alternately, you could do a 3:1 mix of Type N (or Type S for that matter) and add washed pea gravel to it for strength. Sakrete, I suspect, would be cheaper. Think of it as the interior core which will be protected from weather by the skin of Type N mortar.

If the roof will be supported by the walls, you should drill directly into the cement layer, not just the vermic. Buy (mine's a $69 cheapo DeWalt that works fine for light duty) or rent (HD or your local rental place) a hammer drill for this, and there are long bits available for such applications. Make sure the bit is new. It would be better if the walls actually touched the structural slab rather than just the vermic layer so you get a good bond. Consider cutting a channel to the thickness of your walls right down to the structural layer.

There are many ways to form a project like this. Thinking about it a bit more and considering the walls will bear a fair bit of weight from the roof, you might want to use standard reinforcing mesh tied to the vertical rebar (it actually does bend fairly well if you're patient until you get the shape you want). Then you could use 1/4" plywood (very well saturated with water) to bend an inside and outside form in the shape you want. It would have to be very well braced/strapped to prevent buldging. You could then pour in the concrete from the top of the form, using a spare piece of rebar or pipe as a plunger to make sure there are no air pockets. Once the pour is complete, it's standard practice to tap the outside of the form all over with a brick hammer to make sure everything has settled. For weight bearing walls, I suspect you'd need at least four inches in thickness. Uno hasn't been active lately, but I'd welcome his input on this.

You'll need to attach plates at the top of the walls to secure the roof structure. If you're using 18 gauge steel studs, they can be attached with Tapcons once the cement has cured. If you plan on wood plates, J bolts should be placed strategically in the wet cement at the top of the walls. They come with washers and nuts. Drill holes in wood plates, slide over bolts, tighten nuts.

To really nail this one down, I'd like to see a rudimentary sketch.

Projects like this can be tough to comment on at a distance. Hope this helps.

Jim

[waynebergman]

Thank you Jim. This is a huge help. I still have plenty to do with my landing arch work and vent and chimney. So I dont think I will start this wall and roof for a bit yet but its nice to get the shopping and planning out of the way......wayne