another floor question

[trailblaze]

ok so after searching and reading i think i came up with a workable and safe floor idea..

the dutchwest stove i bought calls for a .74 R value or .84 K value for the flooring... so heres what i plan on doing, let me know your opinions

i'll lay a 2x4 down so i get a 1.5 inch raise, then i'll lay some 3/4-1 inch plywood on top, followed by 2 layers of wonderboard (can't find durock anywhere), then apply mortar to that and set 1.75-2 inch stone down.

few questons,

1. would i be at the .75 R value with above design...

2. when layering wonderboard, do i just screw it together or use a quickset

3. does the air space underneath really do anything since i will be putting plywood on top of the 2x4's?

4. would i be better of ditching the 2x4's and just use 3 layers of wonderboard layed right down on my wood floor?

thanks guys..

 

[fossil]

The required insulative property (R-value) must be between the stove and the closest combustible material, so in your plan, the 2" x 4" , the air space you've created, and the plywood do nothing for you except raise the surface of the hearth above the floor. Rick

https://www.hearth.com/econtent/index.php/articles/installing_a_woodstove#protection

https://www.hearth.com/econtent/index.php/articles/wood_stove_clearances_installing_it_safely

https://www.hearth.com/econtent/index.php/articles/k_values_what_does_it_all_mean

 

[trailblaze]

well, maybe i'll put 3 layers of wonderboard down... unless i find something else around here thats a bit better for a layer... looks like wonder board, and hardibacker, and some off brand cement board is all i can find.

 

[SlyFerret]

Metal framing studs work well to build up the airspace with non-combustible material.

-SF

 

[fossil]

Yup, they work just fine, and even provide a wonderful insulating airspace beneath...provided you don't lay plywood atop them, then you start over. Rick

 

[trailblaze]

supose i use metal studs, then lay some sheet metal down...then the wonderboard+stone

would that be the superior way...

what thickness metal would i need to support the weight of the stove and rock/board?? would it possibly be too much weight for my floor?

 

[SlyFerret]

I screwed two metal studs together to box them (they were open on one side) and give a little more strength. Then I put down three layers of half inch Durock and quarter inch ceramic tile. It produced a very solid hearth pad for me.

I put the framing studs pretty close together. I think they ended up being about 8" on center so that I would be sure to have plenty of support.

-SF

 

[thebeatlesrgood]

im in the process of building a heath pad. just need to get it approved from the building inspector b4 i start building it. but micore 300 is a mineral fiber board that offers about 1.2 r so all you would need is -
1. studs (if you want a raised pad)optional
2. 3/4 plywood
3. micore 300
4. 1 layer 1/2 wonderboard
5 then thinset and tile

i couldnt find micore anywhere so i was going to go the metal stud route, but then i came across this website. i dont know how close you are to telford or philadelphia but here goes

(broken link removed)

either way works realy just what you feel would be easier.

 

[trailblaze]

hmm i wish i could get me some of that micore

 

[fossil]

(broken link removed)

 

[trailblaze]

checked it out... nearest place is 6hrs away...

 

[trailblaze]

https://www.hearth.com/econtent/index.php/articles/k_values_what_does_it_all_mean

i'm a bit confused? according to this link... wonder board has an R value of .52 per 1/2 inch right? or is 1 inch...but whats the 1.92 r value at the right side for??

 

[fossil]

That table's pretty hosed up and difficult to interpret. Somewhere along the line, the column headings became misaligned. The best I can make out, Wonderboard has an r-value of 0.52 per inch of thickness...but I can't really claim that this is anything but my best guess. If you find the manufacturer's website, you might be able to get a better number. I know you can with Durock through USG. Rick

 

[trailblaze]

i just sent the company an email... i imagine it's about what hardibacker or durock is in terms on r value...

regardless i'd be using 3 layers... taveling 6 hrs to buy micore isn't cost effective...

 

[begreen]

https://www.hearth.com/econtent/index.php/articles/k_values_what_does_it_all_mean

i'm a bit confused? according to this link... wonder board has an R value of .52 per 1/2 inch right? or is 1 inch...but whats the 1.92 r value at the right side for??

The columns in the table are out of alignment. That is the Rvalue for an inch of cement board. I think something like R .26 for 1/2" is what USG posts. The last column is the number of inches required to achieve an R = 1 value. In this case the article is listing it at 1.92 inches.

 

[trailblaze]

thank you... that helps...

would it be bad to have four 1/2 inch layers of that stuff? so about 2 inchs? i would have to quickset them all together

 

[fossil]

2" of cement board would (it appears) give you an r-value of about 1.04 or so. If that's what you need, or what you want, then that's one way to achieve it. When laying down that type of board, the best way to get a solid, stable structure is to use a layer of thinset adhesive spread with a serrated trowel between sheets, and screw them all together with the specially made screws for cement board. Other screws will work, but the purpose-made screws go in the easiest and do the least damage. Rick

 

[trailblaze]

well looks like thats what i'll do... although my stove requires a .74 r value, so i could use 3 layers of wonderboard with my 2 inch rock and be a little over the r value...better to be over then under!

one last question... hopefully.... What is the type (name) of the saw blade you all used to cut wonderboard??

 

[thebeatlesrgood]

you do not use a saw. score the board a couple of times with a utility knife (they actually do have a knife for that purposes, looks like a nasty hooked blade) then fold it over, score the back and it should come apart. there are invariably little bits of cement that protrude past where you want so lay the board flat on the ground and smash them with a hammer. oh btw i hope you like to sweep and vacuum, because if so youll have a blast.

 

[trailblaze]

ok, i bought that hook/ scoring tool, i thought i read somewhere that someone used a special blade on a circular saw??

 

[fossil]

You can use a masonry blade on a circular saw...half way through your cut you won't be able to see what you're doing anymore & it'll take about a year for the dust to settle. Score & snap is a cleaner process. A course rasp works pretty good to clean up the rough edges. Rick

 

[trailblaze]

thanks for all the help guys!!

i'll score and snap it... even though i'll be doing most of the cuts outside... the way with the scorer sounds a bit easier too...i've been told using a utility knife takes longer and you go through blades like crazy