30"/760mm Scotland Pompeii

[jms]

Re: 30"/760mm Scotland Pompeii

I have a bag of fireclay which I got for the floor. To make homebrew all I would need is lime. Do you know where I can get some?

[Bookemdanno]

Re: 30"/760mm Scotland Pompeii

Your readymix will not harden up at joints larger than 5mm, and the aggregate is too fine to hold together and will slump and pull away from the bricks JMS. Don't use it!

You have two options really, more cuts or get some fireclay to make a batch of homebrew for the outer edge of your joints. Use a sliver of brick to support the dome bricks but leave the joint open at the outer edge. When the mortar has set up a bit, you can point/pack the outer joint with a homebrew mix.
If the joints get larger than 10mm, which they can as you get higher up the chains, i'd even be adding some washed sharp sand to the mix to strengthen the mortar and allow it to hold together in place.

Are this lot near you?

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[GIANLUCA]

Re: 30"/760mm Scotland Pompeii

Using the home brew with extra fine sandblasting sand I made it to the final chain without them dropping. Make sure you dampen your bricks prior it will help the draw of water from the dryness maybe you might have to hold it in place for a minute or two it's really not a big deal you can always use the it loosen it a bit and use a wedge to tighten it up its tough to remove it to the next brick at that height

[deejayoh]

Re: 30"/760mm Scotland Pompeii

If I could un-buy the stuff I've got, I would. But I've got two 25kg tubs and no other use for it.

I'll try mortaring some offcuts together and see how it goes.

You may go through that pretty quickly. I think I went through an 80lb bag of dry (which I would guess is about the same as your two tubs of wet) in about 3 courses. I couldn't stomach the cost of another bag, so switched to home brew at that point. I preferred working with the home brew, once I got the right sand (super fine)

but you shouldn't have any issue with the 10mm gaps at the back. Once the oven is done, the mortar just holds the bricks apart - it doesn't provide any structural "glue"

[jms]

Re: 30"/760mm Scotland Pompeii

A 10mm mortar gap seems to be fine, the offcuts I put together could support a load after an hour without the mortar squeezing out, and a couple of hours later it was pretty solid.

Today I got most of my inner arch cut. Although I ran out of time before I could stick it together.

[jms]

Re: 30"/760mm Scotland Pompeii

Two thoughts: 1) the recommended gap is for a fireplace, not a dome. For a dome, your gap is going to be 0 mm at front and 10 mm at back, so I guess that's 5mm avg?
2) I'd use home brew. you will save money, and I think it's easier to work with!

If I could un-buy the stuff I've got, I would. But I've got two 25kg tubs and no other use for it.

I'll try mortaring some offcuts together and see how it goes.

[deejayoh]

Re: 30"/760mm Scotland Pompeii

A 5 degree angle would equal a mortar gap of 10mm. My premix fire-cement recommends a maximum mortar gap of 5mm. I'll try a test on some offcuts and see how it goes. My main worry is the mortar not setting quickly enough to prevent them slipping down from gravity, and being strong enough to support the next course within 24hrs.

Two thoughts: 1) the recommended gap is for a fireplace, not a dome. For a dome, your gap is going to be 0 mm at front and 10 mm at back, so I guess that's 5mm avg?
2) I'd use home brew. you will save money, and I think it's easier to work with!

[jms]

Re: 30"/760mm Scotland Pompeii

If you are cutting the sides, the only gap you will have is at the back, and my experience is that you don't need to use any brick chips to hold the bricks apart. The angle is a pretty constant 5 degrees or so, which the mortar will easily fill in. Your joints at the back don't have to be all that neat - but for appearances sake I used a jointing tool on the mortar on the backs and that was all it took.

A 5 degree angle would equal a mortar gap of 10mm. My premix fire-cement recommends a maximum mortar gap of 5mm. I'll try a test on some offcuts and see how it goes. My main worry is the mortar not setting quickly enough to prevent them slipping down from gravity, and being strong enough to support the next course within 24hrs.

[UtahBeehiver]

Re: 30"/760mm Scotland Pompeii

Jms
Watch those small brick slivers (chips) better to adjust several bricks than install a narrow one. This is due to mortar creep i mentioned earlier. But a good start.

[deejayoh]

Re: 30"/760mm Scotland Pompeii

I don't think anyone bothers to cut the tops/bottoms. Just the compound cut on the sides.

If you are cutting the sides, the only gap you will have is at the back, and my experience is that you don't need to use any brick chips to hold the bricks apart. The angle is a pretty constant 5 degrees or so, which the mortar will easily fill in. Your joints at the back don't have to be all that neat - but for appearances sake I used a jointing tool on the mortar on the backs and that was all it took.

[jms]

Re: 30"/760mm Scotland Pompeii

The weather yesterday was pretty bad so all I could get done was cutting my stainless steel tube to size and packing it with CaSil.

Today I cut the arch soldiers and linked them with the second soldier course. Linking it up was fun due to my earlier rotation error. My oven's internal diameter has grown by 1", shoddy workmanship

I cut my arch form and was going to cut arch bricks, but then I realised its probably best to let the arch soldier mortar set before I put any weight on it.


Has anyone cut their dome bricks on three sides to reduce the mortar gap? It occurred to me today because I have all this fire-cement mortar to use I will have to pack the gaps with pieces of brick. I was already planning to taper the sides to eliminate inverted Vs.

[mrchipster]

Re: 30"/760mm Scotland Pompeii

Before going any further cover thos gaps between the floor and the dome. You do not want those filling with mortar, it is fine if they fill with ash later but for now get some paper in there and tape it off.

[jms]

Re: 30"/760mm Scotland Pompeii

Thanks for all the advice. In the end I just pushed the floor around by the required amount with some well aimed hits with a rubber mallet. Then I recut the soldier on one side and wedged in a thin slice on the other to make it all link up again, "don't overthink it"

The second soldier course went on pretty simply. I've still got to plan my arch transition so I left those bricks out for now. Cleaning the excess mortar off of the inside face took longer than it did to put them down .

Tomorrow I'm going to put together an IT and plan out the inner arch.

[Bookemdanno]

Re: 30"/760mm Scotland Pompeii

I think i go along with MrChipster. Dry fill the gaps in the floor with sand and fireclay, wrap compress the whole layer with a ratchet strap and simply spin it by the few degrees. If the whole thing moves including the calsil, which is quite likely, that's the lesser of the two evils, and will all be covered up with layers of insulation later anyway. The oven is set straight, the calsil won't matter. You might get a slight overhang of your arch bricks, but you're gonna have CB and Vermiculite handy to fill under if you need.

Its just a case of how happy you are to continue. You'll probably have many of these junctions during the build where you either carry on regardless after weighing up the pros and cons, or you strip back to attain near perfection. Many areas will also be covered up, or not fully seen, so only mechanical properties need to be considered.

Be sure in your own mind of the path you want to take, but like i've been told on here "don't overthink it" too. You can get bogged down in technicalities and imperfections, in what is a very simple and tolerant being.

Good luck with your build, you have made a great start.

[mrchipster]

Re: 30"/760mm Scotland Pompeii

correct. I think if I remove a few of the larger floor blocks then I should be able to rotate the rest around by a few degrees to make it aligned, hopefully without damaging the mortared soldiers. If it won't work I'll just re-cut them. I'll find out tomorrow.

Wrap a wide belt or strap around the entire first layer and attach to a long pole this will put the whole floor in compression and should allow you to rotate it.

If you get a crack or two you can pull those bricks and re mortar.

You may need to have someone holding the CalSil from moving or with another belt in the opposite direction to keep it from moving