house brick for stand, quick quetsion

[Liteceeper]

Re: house brick for stand, quick quetsion

For anybody that may be reading this...a membrane (plastic sheeting) will stop slab cracking from migrating up into your cladding and/or dome.

Croc, too late for that on yours, unless you plan on overlaying the exposed slab with something.

Hi Croc & Stonecutter

Liteceeper here, been crook all week with flu so no action with build but have been researching forum for hints and tips. I know Croc is following my build, not sure about stonecutter.

My question is, as I am also building a brick stand first using a membrane between foundation and first row of bricks, when it comes to forming up and pouring slab do I place a membrane on top of brickwork to isolate slab?

I will follow stonecutters advice and place membrane between slab and perlite insulation render.

Any further advice welcomed.

PS. how do I add a link on signature to build thread?

[cobblerdave]

Re: house brick for stand, quick quetsion

there is no mortar between floor tiles itself but there is mortar under the tiles, doesn't seem to stop the expansion, i can clearly see floor movement so i guess that is good thing other then my front landing bricks and mortar cracks.
my main worry is that water will get in there from rain a lot faster with the cracks open and get in to calsil boards, maybe i will dig out inch of mortar and feel that in with sikafireate
if water didn't worry me i would just leave it, the landing is all made of refractory bricks and they suck water in anyway so maybe i should just ignore the crack? the way my oven cooked yesterday i just could not care less about couple of cracks there.

Gudday
I recon Davids sikafireate should handle those cracks. As you have pointed out those entrance bricks are you Achilles heel when it comes to rain. I have poured a cup of water on mine and you would not believe how fast they suck the water down!
I have a outer cover/door now but before a simple tarp held down with a few bricks stopped that problem.
I suppose overhead cover would eliminate the problem completely but I enjoy the winter sun and being in the open air so I don't consider it an option.
Regards dave

[CrocAu]

Re: house brick for stand, quick quetsion

just had a quick look and all cracks closed up a lot on cool down

[CrocAu]

Re: house brick for stand, quick quetsion

there is no mortar between floor tiles itself but there is mortar under the tiles, doesn't seem to stop the expansion, i can clearly see floor movement so i guess that is good thing other then my front landing bricks and mortar cracks.
my main worry is that water will get in there from rain a lot faster with the cracks open and get in to calsil boards, maybe i will dig out inch of mortar and feel that in with sikafireate
if water didn't worry me i would just leave it, the landing is all made of refractory bricks and they suck water in anyway so maybe i should just ignore the crack? the way my oven cooked yesterday i just could not care less about couple of cracks there.

[david s]

Re: house brick for stand, quick quetsion

You are probably stuck with them if you use mortar. Are your floor bricks mortared together? One reason lots of builders don't mortar the floor bricks is to allow for their expansion. Also an expansion joint/ heat break works well between the floor and the outer decorative arch.You could try filling the cracks with Sikafireate.

[CrocAu]

Re: house brick for stand, quick quetsion

structural slab now have 4 cracks (one on each side), i'm quite positive now that they are heat related thanks to some moisture still in calsil boards, today each crack expanded and since i got the whole thing so hot moisture traveled out the cracks leaving some wet spots at each side, not a lot but enough to crack it.
dome have one (that i can see) hair line crack traveling in mortar to about 4th course of bricks so i'm very happy with this.
if i was starting over with what i know today i'm quite sure i could avoid cracks structural slab but the dome and arch would show up without a question.
the amount of expansion i seen in floor tiles is just crazy, almost makes me feel lucky to only have the cracks in dome and arch that i have now.

question that i do have is my front 4 bricks that seal off calsil board at the front, due to crack in slab and due to floor pushing out from the expansion i have mortar hairline cracks around couple of bricks there, if i fix them after few more fires will they develop cracks again or most likely they would stay crack free?

[CrocAu]

Re: house brick for stand, quick quetsion

was going for another big fire today with no rain in view and got really good temperatures all around
most of the dome went to 1000F with top going 1100-1200
floor was near 1000F
this maintained itself for quite a long time, dome cleared all the way around without any problems.
most of the dome was around 1000F for almost 2 hours after fire died down and all i had left was embers and no real flame anywhere
once floor dropped to 850 i put in 3 arm size logs in push all to left and got on to making my pizza, then came with it after about 15min and put in my first pizza
had no timer going but it was just bit over 1min with single spin about half way mark
and here it is

[Greenman]

Re: house brick for stand, quick quetsion

Hey Croc - Without being an expert I would suggest that if nothing is getting worse then you have a max 0.5mm crack to live with. Wear it like a badge of honour. We all have one if the truth is known. Just make sure that you let those you let see it know that it is there to be admired and not interfered with.

You sound stressed. Have a beer, and a pizza, and another beer.

[CrocAu]

Re: house brick for stand, quick quetsion

my crack opens up a little (back to that max 0.5mm i had before) as i heat up the oven over whole day and slab temperature goes up, then it closes up once temperature drops.
am i guessing right that if supporting stand was too weak it would never close back once temperature dropped so this is good sign and nothing more but cosmetic scar?

[david s]

Re: house brick for stand, quick quetsion

funny story today

48hours after last fire and oven still had around 50C (120F)
slab underside was 26C in hottest spot
so i start my fire and 30min in underside temperature started to go down, how freaky is that, the hotter the oven got the cooler structural slab was at 40min mark it was down to 20C

am i guessing right that my calsil insulation under the floor is finally drying up?

Because it takes a couple of hours for the heat of the fire to get through the cal sil it is not doing anything to heat the supporting slab, meanwhile the slab is losing heat to the atmosphere so still cools down even though you have fire in the oven.

[CrocAu]

Re: house brick for stand, quick quetsion

funny story today

48hours after last fire and oven still had around 50C (120F)
slab underside was 26C in hottest spot
so i start my fire and 30min in underside temperature started to go down, how freaky is that, the hotter the oven got the cooler structural slab was at 40min mark it was down to 20C

am i guessing right that my calsil insulation under the floor is finally drying up?

[stonecutter]

Re: house brick for stand, quick quetsion

You can use membranes on vertical surfaces.

Don't depend on caulk or liquid membranes to span cracking...remember, this is a new slab, and if it the crack widens a liquid membrane has a limit before it breaks and the crack will transfer up through your thin-set and the tile.

Read all the info from the link, it will help you understand how uncoupling layers work. Modern materials for an ancient technique...some floors in Rome had uncoupling layers.

[CrocAu]

Re: house brick for stand, quick quetsion

maybe i just leave gap over the crack on vertical side of slab and instead of grout i use silicone caulk in that spot

[CrocAu]

Re: house brick for stand, quick quetsion

I had suggested this....

that's right, and i think it is great idea which is why i'm going to follow your suggestion just wondering if there is option for vertical surface to do provide same function

[stonecutter]

Re: house brick for stand, quick quetsion

doing so will leave my structural cracks in view so i'm going to tile the slab around, on the top i understand i should use some pvc underlay to prevent further movement around cracks from showing on tiles/grout but how do i tackle the vertical sides? to prevent this problem?

I had suggested this....

I recommend an exterior uncoupling layer, which will prevent any cracks from migrating through your tile and grout.

I don't know what is available to you over there but this is what I use.

Ditra