Hearthstone Homestead owners...

[Ithaca]

I just bought a Homestead (4 in. legs) and the installer said my hearth was fine for floor protection because it was a 'non combustible' floor. The hearth is Black shale stone on a bed of 8 in poured concrete. However I have a wooden joist running through it about 3-4 in. down.

I read in the manual about the floor protection requiring a 6.6 R value and am left scratching my head. All are telling me 'Ahh... your fine", but I want some advice from those who own the thing.

How hot does the homestead get underneath?

 

[Vic99]

First I'd want to know how thich the black shale is. Is there an air space between the shale and the concrete?

Wood that is too close to a stove will get hot enough to eventually cause problems. Essentially, the heat will slowly dry out wood that is too close to the stove. I believe this is called pyrolysis. This will actually lower the temperature at which the wood will combust. Very bad for peace of mind, in my opinion.

However, maybe if these joists are encased in concrete, that changes things. You might talk to a home inspector with a lot of experience. These guys follow the stove manuals

Each inch of concrete has an R value of about .1. Here's a pretty good list of R values: http://www.chimneysweeponline.com/horvalue.htm

I use the 6 inch leg and a bottom heat shield for my Homestead supplied by Hearthstone. This cuts my under the stove clearance to combustibles down to 2.5 R. So I bought a hearth pad with a rating of 3.1R.

This thread has some good info on hearth pads: https://www.hearth.com/econtent/index.php/forums/viewthread/14490/

If you are curious about how hot the Homestead gets underneath, you could use an infrared thermometer and point it at the surface underneath the stove. I have a thermometer that reads to over 1000 F. bought it for about 25-30 bucks from Harbor Frieght. . . . . course maybe you don't want to chance a burn to find out.

The homestead is a good stove.

Good luck.

 

[Highbeam]

You will find that concrete and any sort of tile make for very poor hearths with regards to R-value. Your stone is likely set in mortar right on top of the poured concrete. Likely no air gap. Your stove manual requires an R value of 6.6 which is very very high and hard to get even for the best of us. Your current hearth has a very low R-value and yes, the top face of that wooden joist is the "combustible" that you will measure to when considering thicknesses of materials making up your hearth.

3 inches of concrete, and a layer of black shale. Nowhere near good enough if you go by the book. Will your home insurance company go by the book when trying to decide whether to pay you hundreds of thousands of dollars to replace your home after it burns down? Are you willing to gamble with that?

The easiest way to get a high R-value is to use an air gap. Non-vented air spaces make excellent insulators. Within the dead air space you will have steel or concrete supports for the stove and hearth above.

 

[Ithaca]

Thanks for the replies.

That 6.6 R rating was a shock (once I learned what a R rating was). I am having a hard time understanding why the stove would have to sit on 5'6" of concrete for it to be safe. The Homestead bottom construction is 2/3 soapstone with a cast iron circular grate in the center 1/3, sitting on top of a steel ashpan. The bottom clearance is low under the ashpan compartment at 1/2" to the hearth. One of the reasons I went with Soapstone was the lower temps!! I wish there was an independent testing lab to verify these figures. 6.6 is the highest I've seen and yet the other clearances (side,rear,front etc) are standard.

I guess I'll have to tear up the concrete. Can I get a 6.6 R in a 3" space? It probably makes more sense to get the 6" leg & heat shield option and deal with a 2.5 R rating like clownfish has.

I was hoping other Homestead owners have been down this road before I take the tech's word that all will be swell. I really don't want to sleep in the basement holding a fire extinguisher.

 

[rdrcr56]

Our stove has the bottom heat shield and directly under the stove does not get hot at all, that being said I still built the hearth to spec with two layers of Micor 300 and two layers of Durock. I have wondered why the R factor is so high also, because the hottest I have seen on the hearth with my infrared thermometer is maybe 180 degrees tops, and that is out in front of the stove 6-10 in.

 

[begreen]

Now imagine someone pushing same stove 100 degrees hotter and you'll see why they rate the hearth conservatively.

 

[Vic99]

Yes, I agree with BeGreen. Designers have to assume that the user is going to try to get more out of the product than recommended . . . even if this is by accident.

The 6 inch leg/heat shield works well. The link below shows the company I went with for a hearth pad. I got the cumberland sky hearth pad with thermashield option to get me to 3.1. Basically the thermashield is another layer underneath the main hearth pad. A space between the 2 pieces boosts the R value to 3.1. The top surface of the pad sits about 2.5 inches above my wooden floor.

http://www.hearthclassics.com/hearth_pads/hearth_pad_colors.html

Good luck.

 

[Ithaca]

I guess it is liability issues and 'Worst Case' Scenarios they rate for. I suppose an overheated or runaway stove with the grate open and without the ash pan in place would create a very hot floor.

Either that or they are in dutch with the hearth pad makers.

Great, another project!

Thanks guys.

 

[Vic99]

I know . . . I was just looking at my project list today myself.

You have to plan for the worst, though. Clearly you will not be there to watch your stove 24/7. The manual places a center stovetop temp max of 600 F before overfiring occurs. Sure, there's probably a 5 or 10% safety margin built in, but even so, I have had 3 incidences where I was home and that temp would have been exceeded had I not place a box fan blowing at the stove to halt it at 580 or 590. Who knows if that temp climb has happened when I have not been home . . . the fan always worked though.

Spend $15 and buy a stove top thermometer. It will help you be more efficient as well. I saw a chart somewhere on this site that shows stove heat output at different temps. It is not linear. The difference between 400 degrees and 500 degrees is HUGE, so during the colder days, I try to aim for 550 F. You will get a sense of when to reload your stove to achieve this. It will be trial and error and depend on other variables as well such as tree species, wood moisture etc., but the thermometer will help you understand how your stove cycles much more quickly.