39/42” Corner Building in Brisbane

[Hatzi]

Hi Hatzi,
Yeah spooky isn’t it.
I have only done the one initial render, and no I didn’t add any fibre’s, I didn’t know where to get them either and also didn’t really know if I needed them?
So many posts just said 4:1:1 Sand cement lime so that’s all that went in.
Next coat I will add them if I can find them and I think I will add some Bondcrete as well.
My dome has been closed and drying for about two weeks and as you know it has been hot and dry here, I have paid particular attention to not getting the build wet at all, so I do not expect to have much locked up moisture.I have installed a 2 inch galvanised nipple in the top of the render but will look to see if I can find something else instead, I just don’t like the look of it.
I will do another render coat in a day or two, had a few other commitments this weekend.
Still have not not decided on the countertop after reading your last post, I had not even considered a stone or granite top but now I am, yours look great.
That is the problem with this forum, there is just so much information and every time I look at it I find another build that holds me captivated and has the potential to make me change my mind, and then the hesitation begins again.
I will see if I can find some Ar tomorrow and let you know.
Cheers

Yep, bit the bullet and did my first layer of render today. I used a 4:1:1 mixture. Now just leaving it sit and dry for the next couple of days - or even week and a bit. Depends how busy I get with my return to work.

Have also been very careful not to get the oven wet. I decided to do my curing fires once my perlite layers went on.

Stupid me the, other night forgot to cover it, luckily we only got a little bit of rain, so my insulation layer was a bit damp in the morning. Nothing that our hot and dry QLD weather did not fix up.

Yes agree about the "beauty" of this forum. Mow i am looking for inspiration to complete my outdoor kitchen.

[david s]

I find it is better to eliminate the water from the oven after insulation, but before rendering the outer shell. This way moisture can escape far easier. However it then presents the problem of the dry insulation sucking the water from the render layer leaving it with insufficient water for the hydration process. My solution is to wrap the whole oven in cling wrap after the render layer (I do it in one single layer to save time) . Sponge finish to remove any tooling marks. After 24 hrs you can see beads of moisture under the cling wrap so it works pretty well. Leave it for a week for enhanced strength before unwrapping. (forget this advice if you're building a dog kennel style).

Bondcrete is ok, but a dedicated acrylic fortifier like Lanko Bondit 752 added in same quantity as water to the render mix is better.

I like to add a layer of 10:1 vermicrete over the blanket as rendering directly on to the blanket is difficult because it's a bit springy.

Also, don't render directly against the flue pipe or you're likely to get cracks there that can provide water entry. Wrap some cardboard around the pipe so when you remove it there's around a 5 mm gap that you can fill with high temp silicon.

[Hatzi]

david s once again thanks for your advice.

[Delta]

Thanks Dave,
Well got most of that wrong then.
I rendered straight onto the blanket, didn’t go to bad, only did a thin layer as I planned on doing another two layer on top to get the strength.
I didn’t keep it moist as I thought I would do that with next couple of layers.
I have rendered up the side if the chimney but not on top of it where the flue penetrates as I thought I might cap it with a copper or stainless top?
Hatzi and I are both wondering whether we should be including any AR fibres in the Render?
Cheers

[Hatzi]

Thanks Dave,
Well got most of that wrong then.
I rendered straight onto the blanket, didn’t go to bad, only did a thin layer as I planned on doing another two layer on top to get the strength.
I didn’t keep it moist as I thought I would do that with next couple of layers.
I have rendered up the side if the chimney but not on top of it where the flue penetrates as I thought I might cap it with a copper or stainless top?
Hatzi and I are both wondering whether we should be including any AR fibres in the Render?
Cheers

just another thought Delta, Are you going to do a decorative arch?

[Delta]

Yes but just something simple.
I will just use the angliser program to work out the inner and outer diameters and then cut some thin bricks or stone for a simple arch.
I think I will also leave a small rebate so I can maybe fit an outer door?

[Delta]

Back to it after a week off.
Have decided to do a black polished countertop with a bullnose edge.
Have formed up and sealed the hearth, just got to tie the reo in and can then pour.
I am just going to use a 4:1:1 of builders loam, cement and lime, will add some bondcrete and the AR fibres I found this morning and a jet black cement colour additive.
Have got a shovel full of white marble stones which I will smash up and push down into the countertop top and then hope to polish up when cured.
I figure if it ends up looking like sh*t, then I can just lay tiles over it instead.
Once cured I will restart the rendering of the dome now I have fibres.
Does anyone see an error in my ways?
Cheers.

[Delta]

Hi David,
I recon it is a one (1) kg bag.
Maybe I will call them in the morning to check.
I decided to do th countertop top today and changed my mind and used high strength 55kpa premix, it goes off quick don’t it!
Anyway, happy enough with it, it looks black at the moment and will see how it polish’s up?
Can alway lay tiles if it’s no good.
Cheers.

[david s]

Hi Delta,

My apologies re fibres. I was getting you mixed up with Hatzi. I thought you were looking for a mix to render the outer shell, but now realise you were wanting the fibres for the countertop. I think Lyndons probably sold you the two pack plastic Sika fibres rather than the AR fibreglasss ones. They are good for a slab, but the AR fibres being shorter and softer are much better and easier to work for a rendered coat.
Pictured are the two pack plastic fibres (left pic) and the AR glass fibres (right pic) to show the difference. I used to use the plastic fibres in the render coat, but found I often had to pick out fibres that stuck out from the surface.

[Delta]

Hi Dave,
Thanks for that.
Attached is a photo of the fibres I have.
I didn’t put them in the countertop, late afternoon pour and a high MPA blend which goes of quick meant I was just to rushed.
I intend to add them to the second render coat tomorrow along with some Lancrete 503?
So the countertop came out ok but I didn’t have enough time to pay attention to the bullnose which is what stands out like a third ball.
I got a sanding disc from All Prep Equipment to see what it comes up like, 50 grit and if I kept polishing I think it would look good but am happy with what I got, the white marble chips sank a bit to much so I can’t see them, oh well.
My real issue is that the bullnose needs a lot of filling.
Can it be filled and recovered, or should I cut the bullnose off and have square edge.
I think I will move on to get to a cooking stage and come back to the cosmetic decisions later.

[Delta]

Here are photos

[SableSprings]

Really looks good. The bullnose will be easy to fill/patch with plaster or thinset (or just Portland cement-without the gravel of course ). You might even consider painting it with a contrasting accent paint after filling. Yes, many of us continue to do "detail upgrades" for a long time after the first pizza.

[david s]

Here are photos

They are the polypropylene fibres which increase compressive strength but do little for flexural strength. They are the finer fibres I referred to in the two pack system, fibres in the brown bag, left hand pic. If you add them make sure you mix them around double the time you think as they clump and are a bit hard to disperse. They are also the same fibres you can add to a castable mix as burnout fibres leaving behind a network of mini pipes to help moisture escape without altering the density of the castable. Don't worry they won't reach anything like the 160C at which temp they melt, if you are adding them to the render for the outer shell. They also impart better workability to the render mix. You will find the stuff virtually sticks to your trowel.

[Delta]

Thanks Dave,
Added them to the render regardless, seems to have worked ok.
I now have a furry dome which may help the final colour coat stick better?

[david s]

Hi Dave,
Thanks for that.
Attached is a photo of the fibres I have.
I didn’t put them in the countertop, late afternoon pour and a high MPA blend which goes of quick meant I was just to rushed.
I intend to add them to the second render coat tomorrow along with some Lancrete 503?
So the countertop came out ok but I didn’t have enough time to pay attention to the bullnose which is what stands out like a third ball.
I got a sanding disc from All Prep Equipment to see what it comes up like, 50 grit and if I kept polishing I think it would look good but am happy with what I got, the white marble chips sank a bit to much so I can’t see them, oh well.
My real issue is that the bullnose needs a lot of filling.
Can it be filled and recovered, or should I cut the bullnose off and have square edge.
I think I will move on to get to a cooking stage and come back to the cosmetic decisions later.

You can fill pinholes and voids, then wait a few days and polish. When you are satisfied with your result coat it with a concrete or stone sealer, which will retain the wet look. I first started with an orbital sander fitted with wet and dry paper and adding a minimal amount of water. It did work, but now I have a purpose made angle grinder with variable speed, good electrical cut off and a central water feed with diamond pads in various grades which Velcro on and off. A pretty good machine. My Mum once sanded back a home built concrete shower base with wet and dry paper by hand. It looked pretty good, but hours of elbow grease.
I don't know Lancrete 503, I use Lanko 752, probably a similar product. If added to your render mix it will improve both workability and strength, but use plenty.