Q: Is the new hearth ready for heat? (now with pix and desperate plea for advice)

[Lyndenbrook Farm]

Looking for some advice.

We just laid a new hearth of natural stone for our new-to-us Hearthstone Heritage stove (2003 model).

We used Rapid Set brand mortar mix to set the stones. We finished the last grouting Sunday night.

The package info indicates that this stuff is ready for the weight almost right away, although we have not had the chance to move the stove into position yet.

My question is, how long do you think we need to wait before lighting it up? Should 5 days be enough to allow moisture to come out to avoid making popcorn out of our work?

The stove has a few inches of clearance above the floor and the room has good circulation (including a lot of unintended exchange with the outside that will be addressed when we can get new windows in). I am trying to google up some answers but I am sure someone here has some experience they can relate.

Thank you all for being awesome!

 

[Lyndenbrook Farm]

Oh, forgot to add that I will be posting pix soon!

And thanks mods for deleting my double-post. Not sure how that happened.

 

[begreen]

5 days should be ok, especially for small fires. You'll want to do a couple small break-in fires for the stove anyhow. The Heritage wants a hearth insulation of R=1.2. What is the construction detail of the hearth below the stone?

 

[Lyndenbrook Farm]

The Heritage wants a hearth insulation of R=1.2. What is the construction detail of the hearth below the stone?

The stone ranges from .75-2" thick. Under that is a layer of mortar at about .2" at the thinnest up to the difference with the thinner stones. Then we have cement backer board under that.

The manual included values for the airspace, so we should be well beyond what it calls for

If not .... don't tell me I'm not

 

[Lyndenbrook Farm]

So here is the project before beginning..
And after cutting some rug..

More rocks than we needed ...

The young man who carried them all up from the creek ...

And the mother-in-law who thought this was crazy ...

 

[begreen]

The air space could definitely help as long as their is nothing under the cement board that is combustible and the support framework is non-combustible. If made from metal studs it should be fine.

 

[Lyndenbrook Farm]

The puzzle is complete ...

About this point is where we are totally ready to quit. Squeezing concrete out of an icing bag is not fun on my carpal tunnel thingy. Ugh ...


VICTORY

 

[JTRock]

Super Jealous of your heritage. I wanted one really bad but didn't meet mantle clearance in the fireplace. Nice project you got there

 

[Lyndenbrook Farm]

The air space could definitely help as long as their is nothing under the cement board that is combustible and the support framework is non-combustible. If made from metal studs it should be fine.

Thanks for the reassurance

 

[Lyndenbrook Farm]

Super Jealous of your heritage. I wanted one really bad but didn't meet mantle clearance in the fireplace. Nice project you got there

Thanks! Ours will be out from the mantle a bit.

 

[begreen]

Thanks for the reassurance

Sorry to say that it looks like hearth insulation requirement was ignored.

 

[tarzan]

Where are you getting airspace? I'm puzzled about that and a little worried.

I think you and your family worked hard to build a pretty hearth and I may be missing something but I don't even see half the R value requirements you need.

Excuse me and enlighten me if I'm wrong but I'm just a little to worried about it not to point it out.

 

[Lyndenbrook Farm]

Oh, dear.

We had consulted with a professional and told him exactly our plan. He said it was OK.

Do we not count the airspace between ash-pan and stone?

Oh, dear, oh, dear.

If not, I would say we have an issue.

I would also say "%§&* of a ↨♫*ing ♂↑&%$!"

 

[Simonkenton]

If you don't meet specs, why not install a heat shield below the stove. You could get a sheet of copper, or steel, and just lay it on bricks. It would be 2 1/2 inches above the hearth.

 

[Lyndenbrook Farm]

If you don't meet specs, why not install a heat shield below the stove. You could get a sheet of copper, or steel, and just lay it on bricks. It would be 2 1/2 inches above the hearth.

Yes, such thoughts are swirling in my dense head right about now. Maybe some of that fiber stuff ....

Anyone else have a thought that does not involve jackhammers?

 

[Simonkenton]

I have copper heat shields for the sides of my stove. Copper reflects about 99 percent of the heat that strikes it, so that, with my stove at 500 degrees you can touch the copper, 12 inches away, and hold it with your hand, it is about room temp, maybe 80 degrees.
So I don't ,know if a copper heat shield below the stove would meet official spec, but I have no doubt that it would prevent your hearth from over heating.

 

[Lyndenbrook Farm]

I have copper heat shields for the sides of my stove. Copper reflects about 99 percent of the heat that strikes it, so that, with my stove at 500 degrees you can touch the copper, 12 inches away, and hold it with your hand, it is about room temp, maybe 80 degrees.
So I don't ,know if a copper heat shield below the stove would meet official spec, but I have no doubt that it would prevent your hearth from over heating.

How thick is the copper you use, and where did you obtain it?
Thanks!

 

[begreen]

Oh, dear.

We had consulted with a professional and told him exactly our plan. He said it was OK.

Do we not count the airspace between ash-pan and stone?

Oh, dear, oh, dear.

The professional does not seem to know his stoves. The hearth you have built is ok for ember protection only, but not for this particular stove's requirements. A sheet of metal (it doesn't have to be copper), will create a radiant barrier, but to what extent is unknown if it's just laying on the stone hearth , unless there is a ventilated air gap. But it's probably better than nothing. One solution would be to choose a different stove that has an ember protection only requirement. There are lots of them. Another option might be to bolt a metal heat shield to the legs 1" above and parallel to the hearth. That would introduce an 1" ventilated air space. but that would not protect the hearth in front of the stove where it is likely to get the hottest.

 

[Lyndenbrook Farm]

The professional does not seem to know his stoves. The hearth you have built is ok for ember protection only, but not for this particular stove's requirements. A sheet of metal (it doesn't have to be copper), will create a barrier, but to what extent is unknown, unless there is a ventilated air gap. One solution would be to choose a different stove that has an ember protection only requirement. There are lots of them. Another option might be to bolt a metal heat shield to the legs 1" above and parallel to the hearth. That would introduce an 1" ventilated air space.

Yeah, I may refer to him as a "professional" with super-emphatic air-quotes from now on.

If you or someone else can help me wrap my brain around this, let me see if I have it right:
As of now, I cannot count air space for the R-value because it does not count up to the first solid barrier. But, if there is a solid barrier, then the air space between two solid barriers can add the R-value of air space. So with a plate installed as suggested, then the air space between the plate and the stone counts for R-value, but the air between ash-pan and plate still would not.

I am very grateful for this forum and all you friendly people helping me keep the fire in its nice little box instead of, say, surrounding my family in a panic during the dead of a winter night. Not a pleasant thought.

EDIT: There is about a 3" clearance from the bottom of the stove's feet to the bottom of the ash-pan, so a plate would go in there and give us air space without trouble

 

[jeff_t]

Perhaps the 'professional' wasn't aware that it is an older model? The new ones require only ember protection. I'm not sure what they changed.

I would hate to rip up the great looking, hard work you've already done. Maybe looking for a different stove isn't a bad idea. You can probably get good money back out of the Heritage this time of year. The list of rear vent, ember protection-only stoves is probably kinda short, unfortunately.

Which cement board did you use? Half-inch Durock is R.39.

 

[begreen]

Yeah, I may refer to him as a "professional" with super-emphatic air-quotes from now on.

If you or someone else can help me wrap my brain around this, let me see if I have it right:
As of now, I cannot count air space for the R-value because it does not count up to the first solid barrier. But, if there is a solid barrier, then the air space between two solid barriers can add the R-value of air space. So with a plate installed as suggested, then the air space between the plate and the stone counts for R-value, but the air between ash-pan and plate still would not.

I am very grateful for this forum and all you friendly people helping me keep the fire in its nice little box instead of, say, surrounding my family in a panic during the dead of a winter night. Not a pleasant thought.

EDIT: There is about a 3" clearance from the bottom of the stove's feet to the bottom of the ash-pan, so a plate would go in there and give us air space without trouble

Yes, you understand this correctly. The first solid, non-combustible barrier acts as a radiant heat shield. The heat coming off the bottom and more importantly the front of the stove is highly radiant. When this radiant heat strikes the hearth it heats the surface which then conducts the heat throughout the hearth material. An air gap below this first barrier will act as an insulator. A stove with the door closer to the floor, or an unprotected underbelly is going to heat the hearth more, thus the higher insulation requirement. Older Hearthstones had some high hearth insulation requirements. Be glad this isn't a Homestead.

For a heat shield to be effective in this case it will have to extend 16" in front of the stove door. I'm not sure if raising the stove a couple inches would work as this is untested. Actually most solutions outside of the documented requirements are basically untested. Some will work better than others. One option would be to get an 18" wide, type 2 hearth extension and put it sideways under the stove so that it extends 16" in front of the stove door. I'll see if I can dig up a picture or link.

http://www.woodlanddirect.com/Wood-...ns/HY-C-Black-Type-2-Hearth-Extension-18-x-48

 

[Lyndenbrook Farm]

One option would be to get an 18" wide, type 2 hearth extension and put it sideways under the stove so that it extends 16" in front of the stove door. I'll see if I can dig up a picture or link.

http://www.woodlanddirect.com/Wood-...ns/HY-C-Black-Type-2-Hearth-Extension-18-x-48

thanks for the advice. I suppose ugly is better than dead

 

[tarzan]

from the pics, looks like you used hardi-backer, correct? Any chance you didn't screw it to the sub floor?

 

[Lyndenbrook Farm]

from the pics, looks like you used hardi-backer, correct? Any chance you didn't screw it to the sub floor?

Yes, hardibacker; Negatory, screwed in

 

[Lyndenbrook Farm]

Anyone else with two cents to toss in about my lack of r-value?

Happy to hear more ideas

And please, feel free to call me a dummy. Kinda feelin that right now. So much for consulting a "professional"