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Santino 06-12-2011 08:47 PM

Mother Nature hates me and my hearth
Hey guys, anything I should know to try to help my poor hearth out?

I was about 10 bags of concrete into my pour when the bottom fell out of the sky and the top of my hearth turned into a mini lake. I did the best I could to try to finish it correctly and put 2 tarps over it but I am stressed out about the whole thing. I checked it out just now before I am going to sleep and there's an 1/8" or so of water on the top and it seems pretty sandy towards the top of the concrete. I tried to float it a little (which was way easier now than when it was pouring down rain), but it was dark and I didn't want to make it any worse.

What (if anything) should I do?

dmun 06-13-2011 06:03 AM

Re: Mother Nature hates me and my hearth
If concrete couldn't set under water there would never be any bridges built. You should be fine.

Santino 06-13-2011 07:11 AM

Re: Mother Nature hates me and my hearth
Thanks for your replies guys. I checked it out this morning and it set up for the most part, but it has some puddled spots where it didn't level out very well. Some are as bad as 1/8 -1/4" deeper than the high points. How do I fix this? It seems like most of the spots that are high and low are towards the middle where the dome will go. Once the concrete fully cures, will I be able to build up those areas with sand or fireclay?

I tried to do a cantilevered front and it's a little cracked near the lip. I tried to use the concrete float to pull some of the loose materials and fill that crack in while it's still wet in that area and hopefully it will help it out.

The other problem is that I didn't get to the top of my form before the bags of concrete started going bad, so I'm probably 1/4" away from being a full 3 1/2" of slab for the hearth. I was planning on just putting ceramic fiber board directly on top of the slab (before all this happened), but I am going to need to put an inch or two of vermicrete down now just to get it more level?

azpizzanut 06-13-2011 09:22 AM

Re: Mother Nature hates me and my hearth
Hello Santino,

You have several options. It is a good idea to add 2" of vermicrete to the top of the slab. However, if all you want to do is level out the high/low spots then a thin layer of mortar or 2" of concrete with small aggregate would work too. A 3 1/4" slab is strong enough if you used rebar or wire mesh.

You don't need to put sand/fire clay on top of the ceramic board to level the hearth bricks since the board is ridged and flat. You can put a thin layer of wet sand/fire clay under the board to fill low spots.


Santino 06-13-2011 12:15 PM

Re: Mother Nature hates me and my hearth
4 Attachment(s)
As embarrassing as it is to show, here is what it looks like today after I gave it a spraydown of water. This thread will hopefully teach other newbies not to be as ambitious as I was when there is a even a small threat of a thunderstorm....

1st pic shows side view and puddling.
2nd pic shows layer of sand on top that crumbles just by touching it. Looks like the planet Mars.
3rd pic shows more of the sandy/rocky settling that occured at the top because of the all the excess water that collected before I was able to finish pouring and getting a tarp on.
4th pic shows the high point at the middle of the form with a 1/4" or so drop off going towards the corners.

Hopefully this will show you guys what I'm talking about and help me come up with the best solution for a fix.

Faith In Virginia 06-13-2011 02:33 PM

Re: Mother Nature hates me and my hearth
Personally I would scrape off all the loose stuff and fill in the low spots so you don't have any puddling. Then put a few inches vermiculite/Portland cement mix on top and proceed with your original plans. But that's just me.

I ended up building a cover for my oven. I'm just north of you and I've been getting hit with the same out of the blue storms.

azpizzanut 06-13-2011 02:46 PM

Re: Mother Nature hates me and my hearth
Hi Santino,

Yep, it's a pretty rough job but not as bad as you may think. Just the area under the oven is important since the other areas will be covered or enclosed.

Here's what I would do: Brush off the loose debris then use a grinder or sander to work down the high spots. It doesn't have to be perfect. Then place the ceramic board over some sand/fire clay to bed it. You still have the vermicrete layer as an option too. It comes down to time and effort vs expected results.


Santino 06-13-2011 09:24 PM

Re: Mother Nature hates me and my hearth
Thanks Faith and Bob for your recommendations. I think I am going to let it finish curing over the next couple days and then scrape off whatever is on top. Level out any remaining low spots with a sand/fireclay mix and then place my ceramic fiber boards on top. I was planning for now to just build an igloo enclosure so maybe what I'll do is cover the exposed hearth slab with some type of tile to cover any imperfections.

Is there a certain ratio I should use for the sand/fireclay?

Santino 06-13-2011 09:34 PM

Re: Mother Nature hates me and my hearth
Oh and Faith, you're absolutely right. I was working outside and it was beautiful out. I started to see some clouds WAY out in the distance and I told myself, "I have at least 30-45 minutes if something actually happens." And I definitely would have been done by then and could have covered everything up and been fine. Well literally 10 minutes later, the cloud that looked like it was miles and miles away was sitting over me dumping buckets of rain on me.

Faith In Virginia 06-14-2011 03:28 AM

Re: Mother Nature hates me and my hearth
Santino, rain can be a real show stopper I use this web site and I can predict my local weather to minutes so if you suspect you have some incoming storms you can look at where they're at an how fast it's traveling

NWS - National Mosaic Enhanced Radar Image: Full Resolution Loop

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