Tanzania/Canada

[SteveS]

Re: Tanzania/Canada

Thanks lwood! I will try that for sure. It will be much easier and faster. Just a quick question though. Since I don't have a coating of poor mans mortar around the outside of the soldier coarse do I have to worry about too much heat from the back side of the bricks breaking down the insulation layer?

Cheers SteveS.

[david s]

Re: Tanzania/Canada

If you add sand to your insulating mix it will make it stronger, but will also reduce its insulating value because you are filing lots of the air spaces between the pumice with the sand. The purpose of the cement is just to hold the pumice in place so you can stucco over it. Degradation of the cement in the insulating layer doesn't matter once it's in place.

[SteveS]

Re: Tanzania/Canada

Just thought that I would share a picture of the application of the lower level of the pumice cement insulation. Used the 5-1 ratio. Thanks lwood. Seems to be setting up just fine. Hope to finish the dome tomorrow.

Cheers SteveS.

[SteveS]

Re: Tanzania/Canada

Hello All,

Pumice insulation application is now complete. Thanks for advice on the mix lwood...worked well. Stucco application next...never done this before either. Any advice anyone? How thick?(both rough coat and finish coat or just one coat), what type of finish is better...smooth or textured?...paint?

Any quick advice will be greatly appreciated!

Cheers SteveS.

[cobblerdave]

Re: Tanzania/Canada

SteveS
Here's a Mugs version of Render
The art is to started at the bottom get some mix on your steel float and Push the mix on Up and the the right or left at angle of 45 or so. you can then smooth it of. Remember Push the mortar on and it will stick. Check the pics out and your finish looked alright on the dome but did you play with the mortar with you hands?... we all do I think.
Don't know whats avaliable in Africa as a seal coat at a pinch you could try a flat plastic paint. I say Flat not Gloss as a gloss shows up all the lumps and bumps.... flat is more forgiving and gives you a softer finish
Hope something here helps

Regards Dave

[SteveS]

Re: Tanzania/Canada

Thanks Dave,

Anyone....how thick on the scratch coat and finnish coat?....buttressing needed for arch on vent walls?

Cheers SteveS.

[brickie in oz]

Re: Tanzania/Canada

If you dont provide sideways thrust (buttressing) to an arch it will fail, build some fancy brickwork to the side of the arch.

[SteveS]

Re: Tanzania/Canada

Also....I forgot this question. I've read almost everything on the proceedure for curing. I'm on a bit of a time constraint! All of the dome has been complete for well over a week except the last 10 brick coarse and the keystone which was complete 5 days ago. I must return to Canada in 1 week. Just finnished the insulation yesterday. Hopefully I will start stucco today as well as continue on the chimney. What does anyone think of me starting to go slow with the curing process now so it can be done before I have to leave. I have no thermometer sooooo....if I burn some news paper and then close the door I should be able to keep working....right? Just don't know how long to burn it for to get it to 200 degrees F. The outside temperature here usually gets to about 95 degrees by early afternoon.

Cheers SteveS.

[david s]

Re: Tanzania/Canada

Steve, you should start the fires to eliminate the water from the oven before you do the stucco. Failure to do this often leads to cracks in the stucco layer because of expanding steam pressure. your insulation layer probably needs a week to dry. What has your weather been like? Has is had plenty of sun and wind on it ? You add lots of water to the insulation layer and it has to be removed slowly. Trying to do this job fast is a recipe for cracks.Not that cracks in the outer shell are that crucial, it is only a weather protection thing anyway. I have made the outer shell as thin as 10 mm but usually more like 15mm.

[SteveS]

Re: Tanzania/Canada

Thanks Dave,

How about the newspaper question?

Cheers, SteveS.

[SteveS]

Re: Tanzania/Canada

Also the weather here has been hot and dry but after every step I have kept all my work moist to let it dry slowly....it's just that the insulation layer is so thick! I agree it will take a while for that insulation layer to naturally cure slowly but I don't have the time.

Cheers, SteveS.

[david s]

Re: Tanzania/Canada

If you burn newspaper and close the door it will go out.
You have added probably 50 litres of water or more to that insulation layer. How much fire would it take to boil dry a 50 litre drum of water ? Lots. That's why it is better to let nature dry it out for you. Once the insulation layer has set, keeping it moist to increase strength is a waste of time because the cement in that layer is only there to hold the pumice in position so you can stucco over it. In fact 5:1 is probably way to much cement IMO because it just adds thermal mass where you don't want it. I f you have to start fires just keep it really low, glowing embers rather than flames. Can you use charcoal? just keep it going gently for as long as you can. Should be able to feel the moisture coming out on the outside with your hand.

[SteveS]

Re: Tanzania/Canada

Thanks Dave,

I love the charcoal idea. I have plenty of that. I also have a small hibachi grill that can hold the charcoal for the low slow burn so it is not just sitting on the oven floor.

Now I read that the idea is to cure the oven slowly which I understand lets the oven get used to to the natural expansion and contraction that occurs when you get the temperature up to 800-900 degrees and then as it cools back down to room temperature no cracking occurs.

What your suggesting is that since I'm on a tight time, keep the charcoal going at a sustained low temperature to drive out as much moisture as possible before starting to raise the heat/cool....right?

By the by, my thoughts on closing the door on the paper fire was to do that after the fire was out. I hope you don't think that since I'm below the equator, I think oxygen isn't needed for combustion...lol. Thanks again for quick reply and help on this!

Cheers, SteveS.

[david s]

Re: Tanzania/Canada

Yes,
Crank up that Hibachi and keep it burning constantly but gently, for a few days. Monitor the moisture on the outside, then progress to larger fires until you are satisfied that the moisturevhas gone. Then do the stucco, cover with cling wrap to keep it moist, for strength and you're done.

[dmun]

Re: Tanzania/Canada

but I don't have the time

Decide in haste, repent at leisure.

Think if you have time to rebuild it if you crank it up to temperature too early and get it full of cracks.