42" build in McPherson KS

[david s]

SableSprings I was planning to use vermicrete rather than insulation board. I still have scraps of hardiebacker board.. Do you see any issues with maybe putting a layer of hardiebacker on top of sheets of scrap tile and then pouring the vermicrete layer on that?

Yes you will have to use something like cement sheet to prevent the vermicrete from filling the gaps between the tiles. Remember to also glue some insect screen over the holes, to prevent insect entry, before building over them.

[slschoming]

Took a slow motion video when I broke out my weep holes from the bottom. Kind of neat to see how the water starts to ripple on the surface before the concrete finally breaks.

https://www.youtube.com/watch?v=CjdCK_JcJfw

[SableSprings]

SableSprings ...We're to the point now where we occasionally freeze overnight. Daily highs ranging between 45 and 60 F. I was wondering if I should be calling it quits for the winter, or if I still have some workable weekends. I was also curious if it would be out of the question to do an occasional course of my dome on warmer days in the winter or if I should be planning to wait for the spring.

Here's a link to a pdf document regarding masonry work in cold weather that should help answer your questions. Especially note that freezes can seriously damage/change the curing process and the wetter the mortar/cement mixes are the more prone they are to physical bond breakage due to the ice formation. Based on the information in the pdf, I think I'd start thinking about covering up for the season......unless you tent the structure and give it a little heat to keep it above freezing at night so you can extend your building time further into fall. (p.s. The video of the weep hole punch-up is pretty cool!)

https://www.quikrete.com/media/newsl...nry8_20_12.pdf

[slschoming]

SableSprings Thanks for the help and that document.. I guess I will hang it up until the spring.

[Bethencourt]

slschoming I see you have been using cement boards to pour the concrete of your hearth. did you build support under it towards the center or the corner part? or did they hold strong enough? I'm going to build a 42" and willing to use this instead of wood.

Thanks!!

[slschoming]

Bethencourt Sorry, I did not see your question until today. I did use some minimal wood support under my cement boards. I made legs from 4x4 fence posts and spaced them about 18 inches apart along a 2x4 and propped them under the cement board. Take a look at the photo I am attaching, I realize this is actually when I was supporting a lintel, but it was the same idea. I didn't have to cut any plywood to perfectly fit the space, I just made the concrete board overlap the blocks enough that they were supported, but not so much that they wouldn't allow concrete to bond the hearth with the holes in the blocks. My crude wood supports were pretty tight when I went to take them out. david s gave me the idea to use wedges under the uprights next time to assist in the removal.

The beauty of the concrete boards is that you leave them in place and they become part of the hearth, whereas the plywood forms must be removed.

Hoping to get going again on my build soon. The weather is right, now I just have to find the time again.

[slschoming]

When I hung things up for the winter I was planning to use vermiculite as my insulation layer. I have thought about it over the winter and have sort of shifted gears. I am now planning to purchase some CF board and blanket. It will save me some space and will be easier to put a rigid piece of CF board on top of a sheet of tiles for my weep hole drain channels.

This is the board I plan to buy. I get confused when people start talking about CF board specs, so I am sorry for this uneducated question. Does this seem like it will do the trick for insulation under my firebrick floor?

https://www.mcgillswarehouse.com/hf1...0kgm3-d1af10df

[UtahBeehiver]

Most like will work but to ensure, get the "K" value of the material, should be around 0.5) at 500 F (Standard Units) or 0.079 at 260 C (Metric Units), also need compression strength of at least 75 PSI with 5% compression.

[slschoming]

I sent the manufacturer an email and am now waiting on a response regarding the K value. I searched the forums and it looks like others have used this CF board. In the meantime, I noticed that the 2" variety is out of stock, but I can get the same volume in 1" board for the same cost. Is it acceptable to do two layers of 1" board in place of one layer of 2"?

[deejayoh]

I used the McGill's CF board. Its been great for 4+ years. Can't beat the price either.

1" layers are great, you can stagger the seams

[UtahBeehiver]

If DJ used the board, then great, as long as it is the same product.

[slschoming]

Shipping that stuff to Kansas doubles the price... $213 worth of insulation ships for $207.. I might be going back to vermicrete...

[david s]

Most like will work but to ensure, get the "K" value of the material, should be around 0.5) at 500 F (Standard Units) or 0.079 at 260 C (Metric Units), also need compression strength of at least 75 PSI with 5% compression.

That board has pretty much the same density as 10;1 vermicrete which is considered too weak to support the weight of an oven. There are tons of different products out there, even under the same brand name. My calsil board has a density of 350 kg/m3, considerably more than the product you’re looking at. Make sure it has the compressive strength Russell has already posted.

[Michael Harrington]

I bought 12 18x24 sheets of 1.5 foam glass on ebay 72..00 including shipping the peices arrived with a few dings and some rounded corners over all good shape. I don't know if you could use this instead let me know I can give link he said he had15 left.

[slschoming]

Michael Harrington Thanks, but CoastPizza pointed me to a place nearby that has both foamglas and CaSi board. 70 miles away so I can drive down there.