I am going to build a hearth ( I know there are a lot of threads on this). I have been researching the r-value thing and i see that fiberglass insulation batts have a 3.33 r- rating. So could i sandwich that between 2 sheets of wonderboard to get the needed r-rating underneath my stove? If so would that work on the wall to reduce the distance the stove has to be from the wall?? I only need R=1.2 underneath my stove. Thanks!
Fiberglass batts
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TROY COOK
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Hey there, I think durock has a r value of 1.2 for each 1/2'' I think that batt would be overkill.Plus you will loose r's if you squash it between 2 pieces of D-rock
I'm not clear on your thinking.Are you proposing squashing the insulation between two sections of wonderboard? Lots of questions here, and easy to answer, if you can provide the input- For instance- What type of stove are you planning to use? Brand & model would eliminate 80%+ of the guesswork. As far as insulation, look into - www.thermafiber.com , Sound attenuation fire blankets- Listed at 3.8R per inch. I've got 4.5" of the stuff under my hearth, and I only needed spark protection. Better safe than sorry, correct? Keep us posted-
Compressing regular fiberglass in between sheets of Wonderboard would eliminate most of the fiberglass's insulating qualities. It's the air trapped in the fluffed batts that gives it its insulation value. Mineral or ceramic fiberboard like Micore or Fiberfrax work well here. The link Beetle-Kill provided looks like a similar product.
For the wall shield, there should be no fiberglass at all blocking the ventilated air space behind it. Air needs to flow freely behind this shield.
Cement board, including Durock has an R value of .26 per 1/2" or R .52 / inch. It would take 5 sheets of 1/2 cement board to reach R 1.2.
https://www.hearth.com/econtent/index.php/articles/stove_wall_clear
For the wall shield, there should be no fiberglass at all blocking the ventilated air space behind it. Air needs to flow freely behind this shield.
Cement board, including Durock has an R value of .26 per 1/2" or R .52 / inch. It would take 5 sheets of 1/2 cement board to reach R 1.2.
https://www.hearth.com/econtent/index.php/articles/stove_wall_clear
I have a US stove Co. Magnolia 2015. I am trying to build this thing as inexpensive as i can. But i want it to be as safe as possible. Will probably tile it tho. According to the manual http://usstovecom.siteprotect.net/Downloads/Owners Manuals/2015 Manual.pdf I think it says to have the stove 16/17 in. from the corner of the stove to the wall and like 27/28 from the center. Could i put something on my wall (other than what is in the manual) to reduce that distance to the wall? If so how do i determine how much material per unit of distance? (sorry if i worded that weird)
I made a basic hearth of 3/4 plywood base, several 3' sections of metal studs screwed together (boxed) to make spacers, two layers of Durock on the metal studs, and tile. R is over 1.5, because the metal studs allow airflow between the plywood and the Durock/tile layers and don't substantially conduct the heat. Did the same thing on the wall behind the stove, but made sure to leave a gap at the bottom so air could flow up the wall behind the tile/durock. Only cost about $175 for everything and two days to put it together (including mortar drying time). Make sure to check the mortar brand, not all are good for high-temp applications. If you need, I can dig up the one I used.
Josh25 said:
The manual lists several options for creating a wall shield. Do none of these work? What did you have in mind instead?
The article should be helpful: https://www.hearth.com/econtent/index.php/articles/stove_wall_clear You could also use plain cement board, with doubled-up, cement board strips to create the 1" spacers. The key is to allow air to easily flow behind it by leaving a gap at the bottom and it open on top.
Note, the wall shield doesn't remove the clearance constraints for the connector pipe of 18" for single wall and 6" for double wall.
My MH is a double wide about 16-1700 sqft. Its a 94 model. Doesn't seem so air tight to me. Anyways, Just found the hook up on a bunch of field stone so i want to put down studs, put concrete board n top of that. Then put down the field stones with mortar. My field stones are all about 3/4 of an inch up to about 1 1/4 inch.
That should work on the shield as long as the cement board substrate is held off the wall 1" with non-combustible spacers and it has openings bottom and top for the air to convect behind it. We've had a few folks do this here.
TROY COOK
New Member
LLigetfa
Minister of Fire
It's just you. Even the flammability aspect aside, wood studs can warp when dried by the amount of heat present around a stove.RAMSAY said:
So If I can't find metal studs could I not use wood studs frame my hearth so i can have an airspace?
LLigetfa
Minister of Fire
If you are counting on the airspace to achieve the required R-value, then no, you should not attach directly to wood studs. You would want to have the required R-value to the wood which could be achieved using standoffs.
Josh, the insulation is from the nearest combustible. Using wood studs would place them right under the hearth. That's ok if the hearth is built up to the proper R value, but not ok if the intent is to use the air space to achieve the hearth's insulation requirement. But don't worry, metal studs are used commercially everywhere.
Ramsay, stove hearth requirements vary dramatically depending on the make and model. Some stoves simply require ember protection for a hearth. Other's require very substantial heat protection for the hearth. In the later case, if one can not easily find affordable insulation board locally, metal studs provide a cheap way to increase R Value while providing structure for the top of the hearth.
Ramsay, stove hearth requirements vary dramatically depending on the make and model. Some stoves simply require ember protection for a hearth. Other's require very substantial heat protection for the hearth. In the later case, if one can not easily find affordable insulation board locally, metal studs provide a cheap way to increase R Value while providing structure for the top of the hearth.
The construction of the hearth is different in that the air space is typically captive and not ventilated, though it could be. In a hearth, if metal studs are used, they are the spacers.
The spacers in the article are small pieces of pipe or ceramic insulators. These are fine on a wall because they support no weight. All the weight is on the screws. In a hearth, small spacers won't work because they are then carrying all the weight. There is a risk of them punching right through the cement board with the weight of the stove (and possibly a human) on them. The flat surface of the metal stud distributes this weight.
But this is not necessary if one either builds up cement board to the correct R value requirement or puts the cement board on top of a good insulation board like micore or fiberfrax. That's the simplest hearth construction.
The spacers in the article are small pieces of pipe or ceramic insulators. These are fine on a wall because they support no weight. All the weight is on the screws. In a hearth, small spacers won't work because they are then carrying all the weight. There is a risk of them punching right through the cement board with the weight of the stove (and possibly a human) on them. The flat surface of the metal stud distributes this weight.
But this is not necessary if one either builds up cement board to the correct R value requirement or puts the cement board on top of a good insulation board like micore or fiberfrax. That's the simplest hearth construction.
LLigetfa
Minister of Fire
The hearth requires masonry units capable of bearing the full weight as BG mentioned. Clay bricks could be sandwiched between layers of cement board with mortar to achieve the desired thickness (R-value).
Bricks seem a bit of overkill. One should be able to use doubled up strips of the cement board to achieve the air gap too. If you go this method, space the strips (or bricks) about 12" apart and be sure the top layer consists of 2 sheets of cement board with the seams staggered. There should be zero flexing of the top of the hearth.
That said, if materials like steel studs and micore are hard to come by, I'd just install the 5 layers of durock or wonderboard. It will provide a very solid surface and can be ready for the stone veneer or tiling in about an hour.
That said, if materials like steel studs and micore are hard to come by, I'd just install the 5 layers of durock or wonderboard. It will provide a very solid surface and can be ready for the stone veneer or tiling in about an hour.
LLigetfa
Minister of Fire
Overkill? 5 layers of Durock is 2.5 inches. 2 layers of Durock is 1 inch and a common size of clay brick is 2.25 so overall less than an inch more than you propose.
True - could just use the layers od Durock. However, if you can't find metal studs at Lowes (I couldn't either), your nearest regular building store - local lumber co, roofing co, etc. can get them - a lot of commercial construction nowdays is metal studs. Home Depot here had them too and they're cheap. Alternatively, a local welding / metal shop can sell you like 1" square or 1 x 3" rectangluar tubing - a light gauge like 14-16 is all you will need. May be a little more $, but you wouldn't have to double them to make a box like you do the studs so may work out even, and less work. I think I spaced mine parallel and about 12" apart, the two layers od Durock and the tile / grout above will distribute the load over that space pretty easily. So maybe 5-6 pieces, 4-5' long depending on your design.
LLigetfa
Minister of Fire
I wonder how well metal drywall furring channel normally used for soundproofing would work sandwiched beween layers of Durock?
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