On top or underneath?

[jim81147]

Poured the hearth yesterday , so went to the brick store today to gather materials to get started . While I was there , I noticed a small pile of "splits " sitting all by themselves . when I asked about them the guy told me they did not want to carry them anymore so that pile was just kind of left over . I said that I would give him a quarter a piece for them and before I knew it they were in my truck . So I am thinking they would be good to add some mass with the full bricks on the hearth . Should they go above or below the full bricks? I would guess that either way , they should be laid in a different pattern , yes? Also I started spraying down the hearth today with water to help with the cure and notice that the water flows right through , not standing on top at all . Is that the way it should be ? Thanks for all the input.

[mrchipster]

Re: On top or underneath?

Poured the hearth yesterday , so went to the brick store today to gather materials to get started . While I was there , I noticed a small pile of "splits " sitting all by themselves . when I asked about them the guy told me they did not want to carry them anymore so that pile was just kind of left over . I said that I would give him a quarter a piece for them and before I knew it they were in my truck . So I am thinking they would be good to add some mass with the full bricks on the hearth . Should they go above or below the full bricks? I would guess that either way , they should be laid in a different pattern , yes? Also I started spraying down the hearth today with water to help with the cure and notice that the water flows right through , not standing on top at all . Is that the way it should be ? Thanks for all the input.

Sweet purchase.

Should they go above or below the full bricks?
Below. you want a thicker brick closest to the heat.

should be laid in a different pattern
They do not need to be in a herringbone pattern because they are just a layer of mass if that is how you will use them. A different pattern would be good.

Another use would be to have alternating rings of full and split bricks in your dome. It might look nice.

You sprayed down the hearth? Structural layer? or vermicrete insulating layer?

Structural layer should not absorb much water and should just be misted and the covered with plastic or tarp. Vermicrete should just be covered with plastic or tarp and should not be misted as it has a great deal of water in it and tarp shoud keep it moist enough.

Are your forms still in place?

Chip

[Tscarborough]

Re: On top or underneath?

I would question the need to add mass to the floor, since that is the hardest to heat anyway.

[jim81147]

Re: On top or underneath?

Chip , all the hearth forms are still in place and yes it is the perlcrete layer i was talking about that just let the water run right through . Right now I have both the structural layer and the insulated layer under a sheet of plastic with a tarp on top of that . I am burning a halogen light in the box ( cinder block stand ) under them to keep them warm , thats why i added the water . I just want to make sure there is ample moisture for a week or so anyways. I thought I might pull the forms wednesday or so .
Tom , my thought for putting them on the floor was that I would get a bit of a compromise , not as thick as a brick on edge but thicker than flat .

[Laurentius]

Re: On top or underneath?

Hi Jim,

You might want to give the perlcrete plenty of time to dry out. Watering it down was a no-no, its a sponge and hate giving up the water. A wet insulation under the cooking floor is the primary cause of heat stalling. You're wasting time and energy with the lamb under the stand, better off allowing it to air dry, try a rotating fan.

[mrchipster]

Re: On top or underneath?

Perlcrete will be like a sponge; water will go right in, but you can stop watering it; if you have it covered there is plenty of water there for the week and beyond.

Good idea for a light to keep things warm, I disagree with above post as he probably does not see freezing temps like you are experiencing. I have been doing so with my few remaining tomato plants trying to get the last harvest to ripen. but alas next week looks like it will do them in, no hope after Tuesday next, as it looks now.

Two nights at 25 have bruised the outer parts of the plants that were touching the tarp but tomatoes still look good.

Chip

[jim81147]

Re: On top or underneath?

Hi Laurentius , I had the light under the hearth not to help it dry , but to keep everything warm so that while it was still full of water it would not freeze . Its that time of year here where I live !!!! I know , real bad planning to start an outdoor concrete project , but this is the only time of year where i get a chance. Does the collective think it would be better to remove the coverings during the day? i was always taught that concrete should be kept damp for a while to get a better cure.

[mrchipster]

Re: On top or underneath?

Hi Laurentius , I had the light under the hearth not to help it dry , but to keep everything warm so that while it was still full of water it would not freeze . Its that time of year here where I live !!!! I know , real bad planning to start an outdoor concrete project , but this is the only time of year where i get a chance. Does the collective think it would be better to remove the coverings during the day? i was always taught that concrete should be kept damp for a while to get a better cure.

Keep covered. And should remain damp. and will at these low temps we both have been having. but you are correct it should b kept from freezing for a few days more. Once set it should not be a problem but just to be safe if you can keep it above freezing for a week it would be a good idea.

Another question. Are you going to continue building further into the fall?

Chip

[Tscarborough]

Re: On top or underneath?

Once concrete or mortar has achieved initial set, freezing has no effect on strength. Initial set is defined by no free water in the mix. Best practice is 40 degrees and rising at the time of placing, with no freezing temps within 24 hours of placement.

[jim81147]

Re: On top or underneath?

Yes it is my plan to continue to build as much as i can until I cant anymore . I am not so much trying to get it ready to use as I am trying to get it built and started drying . I doubt that i can get any stucco done this year , which is how I hope to finish the top half , but i would like to get the framing up , the hardiback on and the roof at least on and black papered to keep the weather off of everything. I love the wintertime , but it does come with its challenges.

[jim81147]

Re: On top or underneath?

Tom , with the light burning it is keeping the little tarp tent in the mid to high forties .

[Tscarborough]

Re: On top or underneath?

And by "freezing temps", it is meant the temperature of the concrete/mortar, not the ambient air temp. Covering the concrete will generally allow the concrete/mortar to set well below freezing so long as it was placed with a material temp of 40 or above.

[mrchipster]

Re: On top or underneath?

And by "freezing temps", it is meant the temperature of the concrete/mortar, not the ambient air temp. Covering the concrete will generally allow the concrete/mortar to set well below freezing so long as it was placed with a material temp of 40 or above.

So what I gather from this is that if he wants to keep building he need to keep the structure (Tent) warm and all of his dome bricks and mortar warm prior to placement and he should be good for a while. Maybe keep the bricks and mortar in a heated garage. Here in Minnesota that would mean I would have about another 2 weeks under a tent and then it would be all over. I was able to lay some tile in our sun room two years ago at Thanksgiving but I was able to keep the floor temp at 50 and the room temp at 65 by using two electric space heaters. Outside temps dropped to 10F at night by then. But that room is insulated walls R19 and Ceiling R36.

Chip